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Old 26 November 2009, 12:03   #1
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Tohatsu 2 strokes MW50

Hi,
Was reluctant to work with 3 cylinder 3 carbed engines because these are far more complicated than a 2 cylinder 1 carbed engine, but clients are requesting us bigger engines for bigger boats uses, would like to know if any of you guys have this same engine model in use, what are you experiences if good/bad, if it's a reliable engine, or any comment you would like to let us know. Assume will need state of the art skills to tune well 3 carbs to perform as expected. MW stands for commercial/fishing model.

Happy Boating
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Old 26 November 2009, 12:17   #2
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Boat name: Supacat
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Hi Lucozodiac,
Myself and my friend had these,I say had because his was stolen with his boat earlier in the year.
He had absolutely no problems with his,and I cannot praise them high enough.It may be too early to tell,but everyone who I have spoken to with the same engine swears by them.I have mine fitted to one of our TT-Supacats and it has behaved faultlessly.I have a s/s prop and Boyeson racing reeds fitted to it and the performance is excellent.
Four other people who have bought our boats have the same engine and nothing has gone wrong with any of these yet.

Regards
Howy
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Old 26 November 2009, 12:20   #3
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Hi Again Lucozodiac
I was on about the Tohatsu 50D short shaft,pull start,tiller engine,which I would imagine is pretty much the same,although if the MW is for commercial/fishing I would have thought it would have been even more robust

Howy
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Old 26 November 2009, 16:09   #4
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Ive got a 50 D2 (s.shaft,tiller) same as howy's. The only difference between the D2 and the MW is that the MW has a high capacity water pump and a larger anti cavitation plate. They are a VERY strong,powerful reliable and simple engine which is why our lifeboat service (RNLI) use them on all their inshore rescue boats(engines are rebadged as Mariner), and im sure you know that they are also mainly used in zapcat/thundercat racing.
If you have the Tohatsu maintenance manual then you will see that they are easy to set the carbs/mixture ,timing ect.
All engines have little weak spots, the 50hp Tohatsu's is that after a good while you can find that you can get a weak spark on one plug - most people change the coil thinking that is the cause when 99% of the time, they only really needed to clean the earth up where the coils mount to the block. A common mod that's done now is to add a link wire between the earths on all 3 coils which solves this problem.
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Old 26 November 2009, 17:36   #5
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Hola Howy and Easyrider

A pitty to hear you had your engine/boat stolen, the MW has tiller, crome plated water pump and longer cav plate, know the 50 D model is used on super cats and has it's own category along Yam 50, if you can flip, do minimum service and start the engine back again and continue to race, must be tought engines. The issue I have, these engines are UL (25") shafts, will need to install on a proper boat transom height or raise a 20" transom to match.

Easyrider,would it be posible to send some pics of the cable addition you mentioned so to better grounds. It's a good issue to ckeck/clean/maintain grounds periodically, apply some grease on top earth cables to protect from salt/oxidation. Will you need to rotate plugs when taken out to clean/regap so to work evenly ?

Happy Boating
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Old 26 November 2009, 18:48   #6
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Hi Loco. My engines not that accessable at the moment to take pics. Basically, you just attach an earth link wire to each coil mounting bolt so they're all joined together. If the MW's only come in UL shafts, why dont you just get the M50D2(what we all use here) - you can get what ever length shaft you want then

A friend of mine used to run an early Tohatsu 50 commercially, and ran it for about 8000 hours with just the usual servicing and no other probs - when he changed it for another one it was still good!!!

Ive never bothered rotating plugs, just fit new ones each year. Its worth carrying a spare set of plugs especially when running in as it can foul the bottom plug with the oily mixture , as for some reason they have a bigger main jet on the bottom carb,i havnt got a clue why. The racer boys change the jets to leaner equal size ones(128's i think).
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Old 27 November 2009, 03:15   #7
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Quote:
Originally Posted by Easyrider View Post
Its worth carrying a spare set of plugs especially when running in as it can foul the bottom plug with the oily mixture , as for some reason they have a bigger main jet on the bottom carb,i havnt got a clue why. The racer boys change the jets to leaner equal size ones(128's i think).
It is because the bottom cylinder will naturally run hotter as it gets the cooling water last - more fuel cools it down!
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Old 27 November 2009, 08:21   #8
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It is because the bottom cylinder will naturally run hotter as it gets the cooling water last - more fuel cools it down!
Just a comment, when you start engine impeller pumps water to all cylinders once thermostat has opened, at speed, there is a continous water in-out flow to cool all 3 cylinders at same time, so maybe there is another issue with respect of having a bigger jet on lower cylinder ? Will ask the tech guru.

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Old 27 November 2009, 10:20   #9
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The water has to get in somewhere & out somewhere else..... And both ports are at the bottom of the block. Also at the differnece in mix you'd get with a bigger jet, I doubt it's a case of using the fuel as coolant - more likely the bottom bearing for whatever reason need a touch more oil.

If it;s a fuel mix thing, it may be to do with the pulses of vacuum created in the exhaust manifold form the other cylinders- somehow the bottom one sees a slightly bigger -ve pressure pulse and so needs a touch more fuel to keep the mix the right side of stoichometrioc in there.
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Old 27 November 2009, 16:30   #10
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Originally Posted by 9D280 View Post
If it;s a fuel mix thing, it may be to do with the pulses of vacuum created in the exhaust manifold form the other cylinders- somehow the bottom one sees a slightly bigger -ve pressure pulse and so needs a touch more fuel to keep the mix the right side of stoichometrioc in there.
Fair point but I doubt its to keep stoich levels right as the racers would be blowing the bottom pistons with the leaner 128 jets(std engine has 132 main jet for top/middle carbs and 135 for bottom one). I havnt heard of people blowing pistons/picking up on the bores.

Anyhows, back on topic. Loco- I understand your worries about 3 carbs when youre used to single carb engines, but they really arent a problem at all.
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