stevenmurray1987
Seaman Apprentice
- Joined
- Mar 18, 2010
- Messages
- 41
1989 Yamaha 40HP
2 Stroke
3 cylinder
3 carburetors
oil injected
General picture for reference:
This post doesn't really have a goal. Just wanted to start a discussion on diagnosing a piston slap noise in the crankcase. I found a few old posts, but not a ton of info out there on this. If anyone has any comments, please feel free to contribute.
Have not torn anything apart yet. I'm working my way through a fuel issue and also trying to decide if the noise I'm hearing is a failed wrist/crank bearing. Trying to evaluate the condition of the outboard and decide if I will continue to run it or not.
Symptoms
Bogging/sluggish under load
Suspect fuel/carb issue
Also
Clanking/tapping at low and mid RPM.
Almost sounds like flywheel hitting starter gear but noise comes from crankcase. Doesn't do it at idle, or at WOT. Could just be drowing out the noise though at high RPM.
Suspect piston slap/worn crank bearing or wrist bearing-whatever ya call it. If that is the case I'll probably live with the noise and run it until she spontaneously disassembles.
Did compression test with engine cold, will do it warm later though.
Top and middle were 107.
Bottom was 98.
Plugs- Top to bottom is left to right.
fuel filter- Very difficult to unscrew, good amount of floaty junk at the bottom.
So yeah I am not really asking for advice on anything specific, but very open to any feedback or comments if anyone has dealt with piston slap. Troubleshooting or experience with running an outboard with the condition and how long it ran afterwards. I am not considering tearing into the heads (would be my first) at least until summer is over. Anyways thanks for reading and happy boating.
2 Stroke
3 cylinder
3 carburetors
oil injected
General picture for reference:
This post doesn't really have a goal. Just wanted to start a discussion on diagnosing a piston slap noise in the crankcase. I found a few old posts, but not a ton of info out there on this. If anyone has any comments, please feel free to contribute.
Have not torn anything apart yet. I'm working my way through a fuel issue and also trying to decide if the noise I'm hearing is a failed wrist/crank bearing. Trying to evaluate the condition of the outboard and decide if I will continue to run it or not.
Symptoms
Bogging/sluggish under load
Suspect fuel/carb issue
Also
Clanking/tapping at low and mid RPM.
Almost sounds like flywheel hitting starter gear but noise comes from crankcase. Doesn't do it at idle, or at WOT. Could just be drowing out the noise though at high RPM.
Suspect piston slap/worn crank bearing or wrist bearing-whatever ya call it. If that is the case I'll probably live with the noise and run it until she spontaneously disassembles.
Did compression test with engine cold, will do it warm later though.
Top and middle were 107.
Bottom was 98.
Plugs- Top to bottom is left to right.
fuel filter- Very difficult to unscrew, good amount of floaty junk at the bottom.
So yeah I am not really asking for advice on anything specific, but very open to any feedback or comments if anyone has dealt with piston slap. Troubleshooting or experience with running an outboard with the condition and how long it ran afterwards. I am not considering tearing into the heads (would be my first) at least until summer is over. Anyways thanks for reading and happy boating.
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