I had the opportunity to work with a friend on his boat yesterday and I took the inline scale and a tachometer with me to test the performance of the engine in a static thrust test. We also did this with both the stock 8 pitch prop and a 6 pitch prop.
The tachometer is a Sendec unit good to 7000 rpm in 10 rpm increments.
The scale is a 3000 lb loadcell scale accurate to the nearest 1 lb increment.
I have been wanting to do this for a while as I have the same engine only marketed under the tohatsu brand and it has run weak since I got it. I had assumed that there were problems with my engine but based on the test results I think that there is a much larger issue.
The Nissan engine produced identical test results in RPM and thrust for the static tests with both the 6 pitch and 8 pitch props as my Tohatsu. Both engines with the 8 pitch prop could only turn 3700 to 3800 rpm and produce an average 124 lbs of thrust. With the 6 pitch prop they both turn about 4300 rpm and produce an average of 165 lbs of thrust. With the 6 pitch prop this does produce more thrust at low rpm and in static tests. However on the water this does not equate to better high end performance. The drop in pitch actually needs the engine to turn more rpms to maintain the same speed at the top end. Unfortuanatly even with a 6 pitch prop the engine does not produce enough power to even match the manufactures specified nominal 5500 rpm.
For this engine to output 6 hp it has to be turning the prop at 5500 to 6000 rpm. On the water not tied to a dock the engine will produce a little more rpm.. It will with the 6 pitch prop get to around 4700 rpm. This is still 800 rpm below the 5500 rpm nominal and 1300 rpm below rated max rpm. The difference in 800 rpm on the thrust produced is large, 1300 is simply huge.
My conclusions based on these tests is that Tohatsu/Mercury/Nissan all the names this engine is branded under are over reporting the power produced. Their 6 hp engine produces approx the same output as a 4hp 2 stroke engine.
When I replaced my old 4hp engine with this one I was looking for more power, better fuel economy and queiter operation.
1. Power
The power is the equivalant of a 4hp 2 stroke engine based on static thrust tests (based on testing two engines-one Nissan and one Tohatsu) at the dock. On the water on the same boat that the 4hp engine was pushing the week before , the boat actually lost about 10% of its through the water performance. Going from a top average over the water speed of 5.76 knots to 5.35 knots. I had actually lightend the boat during this time period also in cleaning out a bunch of stuff that had accumulated on the boat. My expectations were sadly let down with this engine. It not only doesn’t give me the extra safety margin I had looked for in a engine 50% more powerfull than my old one it actually is just slightly less powerfull.
2. Fuel Economy
I have to give the new engine top rating for comparative fuel economy. A three gallon tank will give almost 30 nautical miles range with the new engine. This is more than twice the range I had with the old engine. It meets the stated .5 gallon per hour fuel consumtion give by the manufacture.
3. Noise and Vibration
I was expecting a much quieter operation with the new engine and it failed to give that. It is almost as loud as the 2 stroke at WOT (wide open throttle) which is the normal operating speed needed to fight the currents here. Also the engine vibrates even more than the two stroke. The Manufacture told me that this is normal as it is a one cylinder engine. The vibration is bad enough that it vibrates the whole boat at speed and if holding it the engine tiller handle will numb your hand after a while becuase of the vibration.
Another effect of the vibration and a badly designed friction adjustment on the unit is that it will not hold itself straight unless you hold onto the tiller handle. ( the friend with the Nissan version reports the exact same issues) At low rpms the torque of the engine running will instantly turn the engine to the side if not held and at WOT it will gradually twist sideways. For those in dingys and such that use the engine to turn/steer with this shouldn’t be that much of an issue as you are constantly holding the engine tiller handle anyways, but on sailboats (which it is marketed to in the long and ultralong shaft designs) it is a major problem. We have a boat tiller or wheel that we steer with, not the outboard. If not closely monitored it will introduce course changes when your not expecting it while under power.
I would imagine that this data holds true over the entire line of the 6hp engines having these model numbers. Mercury also puts these engines out but I don’t have the model numbers offhand. As to the 4 and 5 hp engines that are based on the same engine and chasis, I have no test data to say how they perform. I can only think that they will be quite weak, as well as having the same issues with vibration and noise.
MFS6BS, MFS6BL, MFS6BUL for the tohatsu’s
NSF6B1, NSF6B2, NSF6B4 for nissan
l just purchased a Nissan Marine 6hp outboard and was wondering if it could be hooked up to a battery for charging purposes model NSF6B 1 year 2010.
A short time ago i bought a Briggs&Stratton 5 HP 4 stroke single cylinder to replace a merc 6 that had died. The Merc put my 12 foot up on the plane handily so in my ignorance I thought a 5 HP would come close and add the benefit of 4 stroke fuel effciency. It did not deliver the former. Its characteristics tracked those described in this article regarding the Nissan 6.
I had a Merc 25 4 stroke on a flattop with which I was quite pleased. The contrast here would seem to confirm that single cylinder low HP 4 stroke outboards will be no means match 2 strokes of comparable HP in performance.
I would add that the Briggs is as the Nissan is described: it is very noisy, it vibrates badly, and it will flip the boat if one doesn’t hold tight to it.
I have a Merc 6HP 4 stroke and it is good for a boat anchor or ballast. Otherwise it is a expensive garage ornament. This motor is loud vibrates and quite simply does not perform. Had it to TWO merc dealers and they both say it is fine. to late for money back — put the old Yamaha back on boat
My experience exactly. As far as I can tell these engines are performing as designed. They just advertise and sell them as a stronger engine than they actually are.
I just recently had the chance to put it on a 8 ft RIB dinghy… it was extremely underwhelming even there. The dealer and tohatsu USA consistently tried to blame my performance issues on how heavy my boat was even though the old engine with less HP did better on it. Well it doesn’t perform rpm wise any better on a 150 lb dinghy.
yes. i know exactly what you guys mean. before i bought a mercury/tohatsu 6 hp two stroke for my tinny i had the opportunity to have a test drive of a suzuki fourstroke 6 hp. i was extreamly dissapointed. for the largest 6 hp fourstroke single cylinder in its class i expected far better results. the boat planed me on my own, the test was done in the flattest of conditions and even the slightest wave would cause the engine to lose rpm. with 2 people in the boat i was gobsmacked at how gutless it was (were also talking a 3.3 metre tinny with no gear just 2 people), i thought that these 4 cylces were meant to have more mid range torque? what a load of bulls%*@!!. whilst all my mates at the time had two strokes i had lots of experience with the 2 cycles and i can say confidently that the 4 stroke did NOT put out the same horsepower as the two stroke counterpart. there was nothing wrong with the fourstroke either as it was a demo model from a dealer. the bottom line with 6 hp being 6 hp, the only difference i expected was a little slower acceleration from the 4 cycle. i was very wrong.
This engine is a little over twice as much than the 5hp Suzuki 2 stroke. I had planned on buying the Nissan because of the complaints I had read regarding the noise and vibration of the Suzuki. From this, it sounds no better. Should I save the extra $700 and go with the 2 stroke?
You are going to get better performance with the 5hp Suzuki 2stroke than the 6 hp Nissan 4 stroke. I’m not sure what the fuel consumption comparison would be or what the noise comparison is going to be but on performance and price the Suzuki wins hands down. If it is a 2 cylinder engine it will also run much smoother with less vibration than the Nissan. Mine and the other 4 strokes run very quiet at an idle and mid range but when you get to 3/4 to full throttle they were not much quieter than the 2 stroke 4hp Johnson i had on the boat previously.
I’m glad that I found out about these problems. I was ready to buy the Nissan 6 hp ultra long shaft for my 25′ MacGregor sailboat. Because of its light weight and fuel economy, it seemed ideally suited for this boat. Does anyone have a recommendation for a motor that will more accurately fit Nissan/Tohatsu’s advertised description for this motor?
Thanks for all your thoughts
Mike
If your bound to look at the tohatsu engines then the 9.9 long shaft would be my go to engine. I have been hearing really good things about some of the Yamaha engines lately but have no personal experience with them.
my 6hp Tohatsu will not idle using California gasoline. I’m told the idle fuel supply line is such small diameter that the ehtanol collects in it and clogs it, thus preventing idle. It runs fine at high speed. I’ve bought a new carburetor increasing it from 4 to 6 hp and have had the idle line cleaned numerous times at $75 per time. Very dissatified!
I concur with the other’s experience. My 6HP Tohatsu produces less HP than the 5HP Tohatsu 2-stroke.
I’ve had good experiences with the Tohatsu/Nissan 2-strokes (3.3 and 5 HP) but am miffed about the 4-stroke 6. It will barely plane one person in a dinghy, something the 5HP did with ease.
I am so glad I stumbled across this web page… Only because it seems that this site contains ONLY the “real deal info” regarding the new 4 stroke engines… Unless your all CRAZY !!! But I dont think so… Just like many of you I needed more H.P and was leaning toward the 4 stroke 6 Hp (Nissan, Mercury or Suzuki) models. for Quietness, Better Gas performance, and lets not forget… better for the enviroment. But after reading these comments, I don’t know now what to get??? My only concern now is if I sink my cash into a new 2 cycle… How long down the road will these engines go the way of the Dinosaurs… There already refused on some Lakes, but you can use a 4 Stroke…. I think we the consumers are getting “STROKED” Michael
BTW : Tom I believe more is involved than just adding a bigger Carb to your exsisting 4 HP to convert it to a 6 Hp rating. even though most of the intial specs look the same…are the “Compression, exhaust ports, Valves” ratio the same ???
Michael,
your best bet if you want more power and smoother, quieter operation is to jump to one of the 2 cylinder 4 strokes such as the 8 or 9.8 hp nissan/tohatsu/mercury engines.. they are what the 4/5/6 hp one cylinder engines should have been for that. They still don’t get as much power as 8 or 9.8 2 stroke would but they are a step up, the downside is that they are about 20+ lbs heavier than the 4/5/6 hp engines and much bulkier. This is an issue in putting the engine on or off the boat or if your boat is real sensitive to weight on the transom.
as to the 4hp to 6hp… changing out the carbs is all that is required. give the guys at internetoutboards.com a call.. they are a dealership that can tell you about it. However it is pretty pricey to buy the new carburetor.
I am looking forward to the day the new generation of e-tec clean and efficient 2 strokes makes it to the low hp engines such as these.
Hello,
I’m buying a Mercury 6 HP / 4 stroke for a 21 ft trailer sailboat. Propeller with 6″ pitch and 8+3/8″.
Do you guess I’m having problems not achieving at least 5 Knots?
Thank you
Alf
Alf,
I’m not sure what kind of boat you have as hull shape can make a large difference in performance but you should be able to get 5+ knots out of this engine on a boat that size.
I have a fairly fast boat it is 23.5 ft long and real world weight is around 4000 lbs… it get 5.5 knots. It does 5 knots easily.
scott
I got this reply from Alf in email and sent a reply back to him.
Hi Scott,
The order was made some days ago and along with the outboard, so it came with a 6″ pitch prop, I had no chance to switch to a smaller pitch.
So, this weekend I tested the new outboard for one and half hour.
The results were ok. At 1/2 the throttle, during the first hour warm up, 5 knots and pretty quiet! At 3/4, 5.6 knots, with some trembling and noise. But not bad.
The only scare i had was when it stopped suddenly when I put it at the lowest rpm. When I did try to restart it, I put previously the gear lever at neutral/idle, but strangely, it remained at forward position inside the gear box. A few tries after, I did achieve to put it really in the neutral position and pull the rope with success. Really on time, when I was a few yards away from the river side wall.
After docked I repeated the process and the same happened. So, the neutral/idle position seems to narrow at lever position. When running, if I move the lever to neutral/idle and stop the engine and after i pull the rope, the gear box is again, by miracle in the forward or reverse position, impeaching any restart, even the lever looks in the neutral/idle position.
Question: it’s a common problem of this motor?
Thank you very much for your help,
Alf
Alf,
I have not had that problem at all on my motor with it staying in gear when in the neutral position. I would call tohatsu and get them to fix it. For something that obvious they should be very responsive. Or call the dealer and tell them.
Your performance sounds good. You sound as if you will be getting 6 knots at full throttle at least.
Let me know what happens.
Scott Carle
I too was looking at the 6HP Tohatsu 4 stroke for my sailboat. I have a catalina capri 22. I just sold my 5 HP Briggs and Stratton air cooled engine because it ran very loudly, and vibrated a bunch. I had to hold the motor tiller in addition to the boat tiller to steer, or the motor would just “walk” out of a straight positition.
Any recommendations…I don’t want to go about a 6HP engine, but would also like one with an alternator.
Thx..Tom
Tom,
This engine runs loud at full throttle though maybe not as loud as an air cooled engine.. not sure I would have to hear it.. your not going to have a conversation near this one in anything close to a normal volume. You will have to raise your voice and strain to hear the other person.
At an Idle to about 1/4 throttle is is fairly quiet.
This engine vibrates a lot.. one cylinder engine pretty much says it all. even tohatsu usa will tell you it vibrates.
from an idle to 1/4 throttle this engine will not stay straight.. the torque turns the engine to the side. You have to maintain positive control of it with the tiller handle. At 1/2 to full throttle the force of the prop in the water pushing against the engine sorta locks it in place. But I have still had it over time turn slowly. Then you have to re-adjust it to keep your thrust from turning the boat.
if you get this engine you need to install some sort of linkage that will hold the engine straight if you don’t want to have to keep it from “walking”
I have a battery management system and at full throttle, just under 5000 rpm the alternator puts out 1.6 amps. thats it!!! no more! the tohatsu manual even states that the alternator is not designed as a charging device but just to run running lights etc.. when operating on a dingy etc..
In extended usage I have found that the alternator does a decent job of offsetting light and instrument usage while the engine is running at full throttle.. It hasn’t had any positive affect in charging the batteries though. The specs say it should put out 5 amps but I have never seen that in real world usage.
Scott
Thanks for all the useful info on Tohatsu 4-cycles. I was going to buy a 6 hp for trolling with a 14′ aluminum boat on a midsize lake to replace the 55 lb. electric trolling motor I’ve been using, but it seems that maybe I should look at the 9.8 for performance and reliability? Am I headed in the right direction?
Thanks again!
I would definitely go with the 8 or 9.8 just for the smoother 2 cylinder action. However performance wise I’m not sure how the 6hp would do on your boat. I just don’t have enough experience with smaller boats like that. I do know I wasn’t happy with it on a rubber dinghy but I have the feeling your boat probably moves through the water better than a rubber dinghy. Even the 6hp will be a drastic performance increase and range increase of the electric motor you have been using. If you use your boat alot though and are used to the smooth quiet of a electric trolling motor then the the 2 cylinder engines are going to be much easier on you. They run much smoother and a bit quieter than the 6hp.
Hey Scott
Greetings from South Africa. A few Q’s if I may, Firstly have you heard of an outboard called a “Parsun” apparently their pistons and alot of the other parts are made by Parsun for yamaha motors and are even in most cases interchangable.
They are being brought into South Africa for the first time by a very reputable dealer of long standing in my home town (Pretoria). The other option I’m considering is two stroke Tohatsu motor 40hp for my 18 ft Aluminum boat which i’ve just finished building.
The Tohatsu is going for about $5000 US the same size Parsun motor is retailing for $3500 US I’m nervous to buy the unknown Brand even though the dealer has given me 1 year warranty plus a promise of good backup service.Have you even heard of these motors ?
Any advice ?
Thanks Steve
Steve,
I haven’t ever heard of them before. I did a little research and word of mouth on the internet is mixed.. they are new to these outboards it looks like and have very limited support and parts most places. They claim that they are fairly reliable with a product test before releasing a model of 500 hours of continues operation. People that have observed them but not used them say that side by side with a tohatsu or yamaha that they look more cheaply built. People selling them say they run good and replacement parts are much cheaper than major brands.
One theme that does seem to keep coming up is that they are the new kid on the block and have few dealerships or service centers and that getting parts is hard. Also that warranty issues are hard to get warrantied. If it was me I would probably give it a miss right now.
however to be honest I was only able to find a handful of references to them other than their own website and advertising.
Scott
I OWN A NISSAN 6HP ITS ON A 175LB INLATABLE W/FIBERGLASS HULL IT WEIGHS 194LBS. BECAUSE OF ITS HULL DESIGN IT W/1 PERSON WILL APROACH 20 KNOTS.THE KICKER BEING W/2 PEOPLE IT WOULD NOT EVEN BREAK 10 KNOTS.BUT I FOUND A FEW TRICKS FOR MORE POWER AND NOW WITH 2 PEOPLE IT HIT 18KNOTS AND 24KNOTS W/1 1ST AND EASIEST TRICK IS TO PULL THE CHOKE OUT JUST A BIT BE CAREFUL TO MUCH AND WILL BOG BUT LISTEN CLOSLY AND YOU WILL HEAR THE RPM DIFFERECE AND SPEED I WOULD SAY 10-15% 2ND TRICK IS A HOTTER SPARK PLUG MADE BY NGK WILL GIVE YOU A FEW MORE RPMS.3RD TRICK IS TO USE 4-STROKE RACING FUEL 1 TO 1 1/2 GALLONS MIXED W/ 93 OCTANE IN 5GALLON GAS CAN BE CAREFUL ONLY BUY 4-STROKE 100 OCTANE GAS THIS WILL NOT HURT YOUR MOTOR AT ALL PROBABLY WILL RUN COOLER AND SAVE YOUR SINGLE HEAD FROM BURNING UP W/ALL THE STRESS ON MOTOR W/87 OCTANE MY MOTOR IS A 2003 NISSAN 6HP THAT STILL STARTS ON 1ST PULL SO ACTUALY W/ A FEW INEXPENSIVE WAYS TO GET 2-3 MORE HP OUT YOUR OUTBOARD. TRY THIS AND I THINK YOU WOULD BE PRETTY SATISFIED GOOD BOATING
I have an 07 Tohatsu 4 stroke 8 hp and a 93 Merc 8 hp 2 stroke – both are great runners. I disagree with the person who said the 4 stroke 8 hp makes less power than a 2 stroke 8 hp. Not so. It runs just as strong as my Merc 8 hp 2 stroke. In fact, the 4 stroke has more torque off the line than the Merc and will go about 2 mi/hr faster top end. Tohatsu torque is 7.1 lb, and Merc is 5.8. Remember that all our cars are 4 strokes, so there must be something right with them. It only weighs 5 lbs more (81) than the Merc 2 stroke (76). Plus you save on gas weight, because you only have to carry half the amount you would with a 2 stroke, and gas weighs 6.2 lbs/gal. I’m an engineer, so I study these things.
Glad to hear your experience. Your the first to have a positive with one of these.. though most of us are talking about the one cylinder 4 strokes. I haven’t really used any of the 2 cylinder engines.
I currently just bought a 1994 5hp 4 stroke long shaft motor. The guy originally said it was a 1997, but turns out to be 1994, so he is offering a refund if I want it. I’m only considering b/c I saw a 2004 Suzuki 6hp 4 stroke for about the same price at $700.00 US.
Any thoughts? Someone told me to stay away from suzuki as they don’t have fuel injection and don’t idle very well.
Thoughts? Is a 1994 honda 5hp better than a 2004 6hp suzuki at the same price and both in excellent condition?
Thanks in advance!
I really don’t have any experience with suzuki motors and couldn’t give you good advice about this. One engine is a lot newer in years than the other.. How many hours is on them might be a good question. If the older one has less hours on it then It might be better. None of the small motors like these are fuel injected, they all have carburetors on them so that shouldn’t be a determining factor. I would wander into a outboard repair shop and see if I could talk to a mechanic that has been doing this for a while and ask them their opionion of the models. I do know just on general reputation that honda’s are known as top end for quality but that their engines tend to be a bit heavier than anyone else’s engine of equivalent HP.
Hope this helps but I don’t really have anything else I could say about it.
Scott
Scott, thanks so much for the quick reply. I will call a local marine repair shop and see what they think. Also, I was mistaken. My friend said Susuki’s don’t have a fuel pump, whereas the others do, so they don’t idle or run very well at low RPMs. Thanks again!
Brent
Which 3 to 4 hp engine would you buy for an inflatable tender?
Thanks!
I have used a 3.5 hp tohatsu recently and it did well. Not sure if its power is as rated but it cranks easy and runs fairly smooth. The small built in tank seems to be both a positive and an negative depending on your viewpoint. It means you don’t have a external tank and line that can be a pain. However its range is limited on the internal tank only. You would want to keep an extra gallon or two tank in the dingy to fill up with most of the time if you ran out. One of the torqueedo electric motors with an extra battery might be a good solution if you don’t do a lot of long range motoring in the dingy. I think that any of the outboard manufactures motors in that range would be comparable.
I have had a nissan short shaft 6 4S on my Catalina 22 for five years and it pushes it fine. It has always pushed it at hull speed (5.5knots) and usually at just 3/4 throttle. I have a Nissan 3.5 and there is no question the six has more power than the 3.5.
It is much quieter than my old 2s, but I did not think that was a fair comparison and of course it is quieter at low speeds.
There is vibration, I once suggeted you place a plastic cup on top the engines and see at what speed it falls off.
I have an old 8 hp Envinrude and it has more power.
I am in the opposite boat (pun intended). I have a 13′ aluminum and need less hp and weight. I currently have a 7.5 hp Honda and it is way too heavy to lift in and out. It also pushes the boat too fast for trolling. Not having to deal with the oil and smoke is a big deal as well as quietness. The noise level seems to be a problem. Is that just under throttle or at idle or both?
At an idle there is little noise. It is only at higher rpm that the noise gets excessive or 2 stroke level. For trolling I think this engine would work well. At full throttle it will most likely push your boat at 8 knots or so but will vibrate a lot. I am just guesstimating the speed as I have not seen one on a little aluminum boat. On a 7 or 8 foot RIB (rigid floor inflatable boat) dingy it would not get up on plane.
Does anyone have experience with 6 HP, 4-stroke Suzukis versus the same version of Nissan / Tohatsu?
JB
Jb,
I haven’t worked with any Suzuki engines at all so wouldn’t be able to give you good advice there. Mabye someone else reading this will be able to.
Scott
I have a 2006 mercury 6hp 4 stroke. I have it on an inflatable. It halls ass with one person in it, but as soon as you put the dog or the 110 pound wife in, it does not want to plane. Anyone know how I can get a little more hp out of this motor? Thanks any tips would be appreciated.
If it is hauling ass with just you and the inflatable (ie getting up on plane then it is doing more than mine would do on an inflatable already. wish I had some advice to improve the performance. maybe going to a smaller pitch prop.
I’m getting ready to purchase a 6hp for a 14 foot flat bottom. I need the lighter weight since I will be hauling it around by myself. Is there a difference in the 2010 models? Which one would you purchase?
I haven’t seen the 2010 models so could say if they had made any changes.
Scott, I have a 24 foot sailboat that weighs 4000#s. The previous owner had a 9.8 HP Nissan which was more than enough (never got to above 1/2 throttle) but it was heavy to raise and lower on an auxillary mount. I also want to be able to take the engine with me as the dock is not very secure, again the 9.8 HP is too heavy to easily remove. So I was thinking the Sail Pro Tohatsu would be ideal – (though somewhat concerned about power from your posts but 5 knots should be fine) however, I like to camp out overnight and if your saying it can’t charge a battery than that seems like a no go. Your thoughts? Steve
Steve,
The alternator on the 9.8 is the same as on the 6hp as far as I’m aware.. don’t hold me to this but I think it is true.. However tohatsu/nissan themselves in the manual specify that the alternator is not for charging batteries but for running the running lights on a small boat or dingy when operating at night. I found that at abou 4800 rpm which is about the best that my engine can do that I only got about 1.6 amps out of the alternator.. according to tohatsu is should give about 5 or 6 amps at WOT of 6000 rpm. I have never seen one of these engines actually make that rpm so you will probably have to live with the 2 amps or under that I have observed/measured. You will find that at about 60lbs this engine is easier to remove than the 9.8 but that doesn’t mean it is easy. It is an awkward handful. You will find that the 9.8 Nissan is a smoother and more powerful engine that if it is the 4 stroke version is also significantly quieter than the 6hp. The 9.8 has two cylinders vs the 6hp one cylinders. this makes it much smoother. If it is harder for you to get off it is harder for a thief to get off the boat. I would invest in a really good lock and keep that engine on the boat., maybe an outboard lock and a cable lock if you wan’t to go crazy. Also painting the engine something other than stock to make it very distinguishable will lower it’s steal appeal a lot.
scott carle
Scott,
I am debating between the 5hp Tohatsu long shaft and the 6hp Tohatsu Sail-pro long shaft. I borrowed a friends 5hp Tohatsu and liked it very much (smooth quiet sipped gas and no smoke). But was thinking about the Sail-pro for the “extra” 1hp and the alternator charging the battery (on long day trips jamming the tunes, overnight lights, and maybe a refrigerated cooler?). I would stick with my 25+ yr Mercury 9.9, but she is heavy, smokes alot, and likes to stop running at various times of importance. I have read the present 4 cycle engines are less pwerful than the 2 stroke engines, and can accept that. I am looking for a quiet, dependable engine, to get me in/out of the marina and in an emergency across the bay in a hurry. Should I go with the 5hp or go the extra $$ for the 6hp? Without looking it up do I understand correctly, the 5hp has 2 cylinders vs the 6hp has 1 cylinder. Would the 2 cylinder engine run smoother cause the opposing cylinders balance themselves out? Versus the one cylinder with no counter balance. What’s your recommendation between the two? I will be using on a 22′ Morgan sailboat (4000lbs) on the Chesapeake Bay.
ed
Ed,
The 5hp tohatsu and the 6hp tohatsu engines have identical power heads on them other than the carburetor. They are both a one cylinder engine. If you want smoother and quieter then bump up to the 8 or 9.8 tohatsu which are two cylinder engines.
The tohatsu 5hp long shaft is 20 inches. I really really like the 25 inch ultra long shaft of the 6hp (sail pro) or the 9.8 25 inch shaft. I don’t believe that the 5hp or the 8 hp engines are available with the 25 inch shaft.
The 6hp engine vibrates a lot due to the one cylinder and at WOT (wide open throttle) is very noisy.. about as noisy as a two stroke engine. It does just sip fuel. I have gone about 100 miles on 12 gallons of fuel in my boat (at beneteau first 235 at about 4000 lbs loaded weight.) The 9.8 engine is a much smoother quieter engine with an extra reserve of power. You will most likely only use it at half throttle most of the time while with the 6hp you will use it at WOT most of the time to get to hull speed if it is able to push you to hull speed. The 6hp engine if money is an object will work for you but you need to get the 5.99 pitch super high thrust prop.
Scott
2007 Mercury 6hp longshaft (changed prop!)- Catalina 22
I dont care about noise – as its on a sail boat… but is it nosy at high revs!
I dont care about vibration as is switched off when I am enjoying the boat – its about the same as my old 2 stroke Evinrude sail master 6.
However, (and now I’m going to ruin my resale price) its absolute junk when trying to start it each year and when I get it going it cuts out after five minutes use and will never tick over properly (even roughly)! Its been to the deal twice – who seem to be able to fix it (under warranty)
I have pretty good mechanical knowledge! (being a British antique car restorer and rebuilding/repairing various engines)and I cannot believe that this engine in 2007 needs so much care and maintenance and just does not work as advertised and intended.
Ayone whant to buy mine I repaired the Evinrude and it works great now!?
I am looking at buying a new (2nd owner) 6hp Nissan 4 stoke for a zodiac dingy. The dingy is approx 9 ft and would prob be pushing just under 450lbs combine total weight. I am not replacing an old engine, buying one for the first time. Do you think this is the way to go if the price is right? Dingy and motor being sold together.
Roger,
That engine is a reliable and economical engine but I fear that is is under powered for that dingy.It is the equivalent of a 4hp 2 stroke. It will work but im not sure it will get it up on plane. If you can take it on a test run before buying it to see if it actually can get it up on plane I would. If your getting an increadable deal on it then it probably doesn’t matter. You should be able to sell the engine at a later date to get a bigger one. Also if you don’t need the speed to get up on plane then you will be ok.
I recently purchased an 8 hp merc 4 stroke for fishing use, but found it is too heavy for both my light aluminum boat. But it trolls great – quiet and rather smooth ( a little vibration but not a problem), which is why I got it. I am considering trading for a 6 hp but am concerned about the possible increased vibration, being a single cylinder, at slow trolling speed. Any advice?
The 6hp at trolling speeds is fairly quiet and smooth.. not as quiet and smooth as the 8hp 2cylinder you have though.. At anything over 1/4 speed it will vibrate 3 or 4 times as much as your current engine and be about as loud as a 2 stroke engine. I have been extremely disappointed in this aspect of my 6hp 4 stroke.
I saw a 6 hp for sale and it had a turnbuckle mounted on the motor and then to the boat. I did not understand why until I read all of these statements now I have to re think what I need now that the totsi is not going to be an option. Thank you Scott for your info. Rick
Glad it has been helpful for you Rick.
Scott