Yanmar 1GM10 revs die and slow speed

[kevsbox]

My boat is fitted with a Yanmar 1GM10 , recently I have noticed the top speed has decreased, I used to get able to get 6 knots, now she struggles to 4. I have also noticed that at full throttle the revs die off (you can see/hear this here -

.
I have checked the prop and shaft, all clean with no snags. Fuel looks clean in filter and no sign of leaks. Air filter is less than 1 year old also.
Any ideas folks?

 

[Biggles Wader]

Is your bottom clean? The boat I mean

 

[RichardS]

Have you checked whether the exhaust elbow is partially blocked? I would recommended that as the first port of call.

Richard

 

[kevsbox]

Have you checked whether the exhaust elbow is partially blocked? I would recommended that as the first port of call.

Richard

Hi Richard, yep done that, all clear

 

[kevsbox]

Is your bottom clean? The boat I mean

Hi, yep bottom is fairly clean (boat that is). She was cleaned and anti-fouled 18 months ago, due to come out again this winter but i went under a couple of weeks ago and no problems, also checked prop and shaft at the same time.

 

[garymalmgren]

Check that the Morse cable outer sheath is clamped to its mounting tightly. At both ends.
Also check the the inner cable is clamped well to the throttle arm and at the control end.

You may be lucky and find that it is a slipping cable.

gary

 

[kevsbox]

Check that the Morse cable outer sheath is clamped to its mounting tightly. At both ends.
Also check the the inner cable is clamped well to the throttle arm and at the control end.

You may be lucky and find that it is a slipping cable.

gary

Thanks Gary, I will check that out next time I am on board.

 

[Tomahawk]

Fuel looks clean... but is the filter clean?.

 

[garymalmgren]

Kev
Are you pushing the control lever with your foot because it is stiff or that is your way?
Stiff Morse cables can be loosened by removing, hanging vertically and pouring warm kerosine between the inner and outer sheath and inner cable.
They can some times get gunked up with salt, sand and dried grease.
Don't grease them.

 

[Refueler]

At one time I had similar ... revs dropping off shortly after starting ... I checked everything and finally found it was a bit of crap in the tank bottom basically sitting in the 'well' ... I'd start engine ... all fine ... then that bit of c**** would suck onto fuel pick up and restrict fuel ...
Cure ? I Pela'd out the fuel ... after giving a good stir as possible even with the baffles - the fuel moved enough ... then let it settle .. then filtered - put it back.
No more drop of revs.

I was surprised as I never thought fuel draw was that strong ..

 

[kevsbox]

Fuel looks clean... but is the filter clean?.

I will check that out

 

[kevsbox]

Kev
Are you pushing the control lever with your foot because it is stiff or that is your way?
Stiff Morse cables can be loosened by removing, hanging vertically and pouring warm kerosine between the inner and outer sheath and inner cable.
They can some times get gunked up with salt, sand and dried grease.
Don't grease them.

I use my foot because it is low to the ground, next year I hope to raise the control