Bought this boat back in April with 70 hours on it. Have put about 200 hours on the 3 cyl yanmar
40hp. So, 270 hours on it.
I noticed a progressive issue about 40 hours back.
From day one, it seemed like the engine
just took a good 10 minute warmup or so to idle smoothly. I figured that was normal. Eventually, it seemed as though the fully warmed engine
was not idling smoothly. Sometimes, another few minutes under power and it would idle fine. Sometimes, not. Now, it pretty much tries to shake the boat apart at idle no matter how long it's been running.
It doesn't matter if it's in gear
or neutral, it shakes like hell.
It doesn't smoke. Motor
mounts look good. Idle is set at 825-850. It operates at full rpm
, although there may be a 100 rpm
or so drop in max speed. Not sure about that.
It starts easily, accelerates smoothly, shuts down easily, etc.
Both the primary and secondary filters have been changed, recently. No evidence of fuel
issues found there.
One curious issue- when opening the bleed screw on the secondary filter system, I had to pump the little lever on the fuel pump
about 25 times before fuel
appeared. However, it was solid fuel when it appeared. Also, that bleed operation had no effect on the idle shaking.
Advancing the the throttle instantly stops the shakes. However, advancing it to say, 900 and then stopping, the shakes come back, immediately. Around 1000 rpm, the shaking becomes what I would call normal although I hear a slight knock, like one unhappy cylinder.
The idle stop screw is tight and the plate is firmly against it.
I'm ruling out cable stretch, motor
mounts and filter issues.
Time to pull the injectors and clean them?