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AQ151c crankcase breather problem?

P

Paul McClure

Member
I've just had the engine put back in the boat after a total rebuild (big end bearing failure) and have been trying to dial in the carb (Weber 38DGES with electric choke). It runs fine then dies after a few minutes. However today I noticed that there was fluid bubbling up from the crankcase breather hose, which then dumps into the carb and the engine dies. I disconnected the hose and put it in a bucket and it was running fluid out, with more coming out as I hit the throttle. The fluid is oily / fuel-ly...

Any idea what is causing the problem? Thanks in advance.
 
Thanks for your reply. We've still not got it fixed - need to do an oil change to get rid of the contaminated stuff before running - then back at the carb. It's an over-fuelling problem, either excess fuel pressure, which I doubt as it's still on the mechanical pump, or the float/needle valve not closing on the idle circuit. Excess fuel drowns the motor, a load ends up in the sump. The level in the sump rises and get to the point where pressure forces it out of the breather hose.

I'll post again once we have sorted the problem to confirm. FWIW compression is good on all cylinders.
 
Sounds like the fuel pump diaphram is shot and leaking fuel into crankcase and the clear line from the pump. Change it and make sure it is marine rated.

Quite sure that is your problem.
 
Agree with robj. And the Weber does not like the higher psi output of the mechanical fuel pump. I put in a pressure reducer and have it set at 3psi. works well.
 
The pump is a new one, we may swap it out for the original one, which was fine. The pressure reducer may be an option, we'll investigate that after verifying the carb is OK.
 
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