No bottom end power in M40C tohatsu

T

tt600

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I just bought a '95 M40C. It runs fine on top and is faster than my 35hp Johnson was. However it has so little bottom end that it stalls when I shift into gear. I had to detach the block so I could get it to start in gear and then use starting fluid to get it going with the throttle revved. In my experience this is either a clogged pilot jet or low compression however tohatsus are new to me. Does this sound familiar to anyone? Ideas? would it run so good on top with low compression?
 
pvanv

pvanv

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Re: No bottom end power in M40C tohatsu

Might just need a proper carb cleaning.
 
Sea Rider

Sea Rider

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Re: No bottom end power in M40C tohatsu

Yep, as stated, just needs a proper carb cleaning or mix or idle screw out of correct adjustment, too low idle revs, stalls when shifting into gear. Those are rocket proof, simple engines.

Happy Boating
 
TOHATSU GURU

TOHATSU GURU

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Re: No bottom end power in M40C tohatsu

It could be anything from the fuel system to a bad block...Testing if you have a manual or shotgun parts replacement if you don't.
 
T

tt600

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Re: No bottom end power in M40C tohatsu

TOHATSU GURU said:
It could be anything from the fuel system to a bad block...Testing if you have a manual or shotgun parts replacement if you don't.
Click to expand...

I took apart the carb today. all jets we not clogged. the idle mix screw was at 3/4 turn out. I set it to 1 1/2 turns. reassembled and tried to start. it was a little difficult but one shot of staring fluid and it started and idled fine. Then started easily thereafter. I shifted into gear and it ran fine. however this was in my driveway with muffs and no load. I guess I need to set up a barrel of water so it will have a load on it.
 
Sea Rider

Sea Rider

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Re: No bottom end power in M40C tohatsu

You must readjust idle rpm at neutral on water, adjusting on a barrel needs slight less revs, once on water engine will probaly stop. With engine fully warmed up, adjust idle screw enough so that when shifted forward you hear a dry clak and engine doesn't stop, readjust slightly CC if needed till correct adjustment is achieved.

Happy Boating
 
Last edited:
T

tt600

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Re: No bottom end power in M40C tohatsu

Well, finally got a chance to test my motor. it now seems to run fine. Not sure if adjusting the idle mix screw 3/4 turn was what did it. I am currently running a 12 prop on my motor which is good for light loads at 3600' on my 16' alum boat. I think i will have to get a 10 prop for high altitudes.
 
T

tt600

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Re: No bottom end power in M40C tohatsu

TOHATSU GURU said:
Are you running it above 3000 feet?
Click to expand...

About half the time I am above 3600 feet and half below. in the winter I go lower and the summer higher.

as the Tohatsu guru do you know any sources for a M40C hood handle? Mine is missing.
 
TOHATSU GURU

TOHATSU GURU

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Re: No bottom end power in M40C tohatsu

Any Nissan or Tohatsu dealer...Except me as iboats does not want me to offer to sell anything. Your engine is drowning above 3000 feet, but dropping down in pitch will help a little.
 
T

tt600

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Re: No bottom end power in M40C tohatsu

When I look at online microfiches for parts it lists the hood handle as obsolete. I am only finding certain parts available for this motor. Any other sources you know of.? can dealers get obsolete parts? now tohatsu makes a 3 cylinder 40. Weighs 30 lbs more. Mine is 132 lbs.
i tried running with an open intake and no cover at higher altitudes as a way to lean it out. Didn't seem to help much. should I
Get two sets of jets?
 
Sea Rider

Sea Rider

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Re: No bottom end power in M40C tohatsu

Ideal would be to have 2 carbs and 2 props, a standard one with factory delivered prop for sea level use and the other jetted for higher alttude use along a less prop pitch to pull revs bit higher. A much faster carb swap than rejetting including tearing carb down frequently...

Happy Boating
 
TOHATSU GURU

TOHATSU GURU

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Re: No bottom end power in M40C tohatsu

The handle is available from any Nissan or Tohatsu dealer and is not obsolete. Dealers can not get obsolete parts as they go obsolete after they are not available anymore. You would normally get the high altitude jets and then change back and forth as needed.
 
pvanv

pvanv

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Re: No bottom end power in M40C tohatsu

Any dealer can accommodate your need. The handle part at the back of the cowl is 345S675210 TILT HANDLE $22.19, available from any dealer, several of whom are forum members, including Elvin... even me :)
 
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