M40c Loud exhaust noise comes and goes.

[sailhard]

Hello,

I was out with My tohatsu m40c last weekend and under full throttle after a few seconds, the motor started making a loud exhaust farty noise, as if the exhaust was not coming out the prop bet elswhere. I slowed down and it stopped but it come back under high throttle. Now I'm worried I have a head gasket starting to go or worse.

I haven't really looked at it yet so it could just be a loose sparkplug but I thought I'd throw it out there.

I have a shop manual now, but found nothing about intermittant exhaust noise....I think I will check the exhaust cover too...

 

[TOHATSU GURU]

Re: M40c Loud exhaust noise comes and goes.

Something blew...Check your compression before you run the engine again.

 

[sailhard]

Re: M40c Loud exhaust noise comes and goes.

Hello,

Thanks for the reply, TG.

I checked the compression, my manual says it should be 107psi, but both cyls were close 120psi. I tightened the exhaust cover bolts and powerhead bolts. Then I took it out for 10 minutes or so and it seemed fine...

I'll take her out this friday and see how she does...

 

[TOHATSU GURU]

Re: M40c Loud exhaust noise comes and goes.

Don't worry about the number itself. You just want the cylinders to be even. While it's possible a series of loose bolts could allow an exhaust leak I would say that normally they can't get loose on their own as old as the engine is.

 

[sailhard]

Re: M40c Loud exhaust noise comes and goes.

Don't worry about the number itself. You just want the cylinders to be even. While it's possible a series of loose bolts could allow an exhaust leak I would say that normally they can't get loose on their own as old as the engine is.

Yes it is strange, but I've run it for several hours now without issues.(??)
My wife complains that it is too loud though, so I think a 4 stroke is in my future. Does tohatsu offer a 40 hp 4 stroke?

 

[TOHATSU GURU]

Re: M40c Loud exhaust noise comes and goes.

Nope. That went with DFI in the 2-strokes.