Hard Starting when warm

dobler5

Seaman Apprentice
Joined
Apr 13, 2010
Messages
31
Hey guys, I have a 1990 OMC Cobra 4.3L with brand new 2BBL holley carb. and a brand new electronic delco voyager distributor with a brand new fuel pump as well with new spark plugs. Here is my problem, I took my boat out and everything was running good on my first 4 tanks of gas. Approximately 25 hrs or possibly more. Now after running while the motor is very hard to start after running around for awhile. Whenever the engine warms up in takes quite a bit of cranking over to finally get it to fire up and start again. Black smoke comes out of the back of my boat when getting started. I am noticing that oil is coming out of the breathers going to the carb. Not a whole lot but the cover on top of my carb is slighty oily. I notice from draining my oil from last 50 hrs that it was a quart short of what I put in there. What can be the cause of this hard starting now after there was no problems a couple of days right before my engine started doing this. Any help to check would be awesome! Thanks guys
 

CobiaXL

Banned
Joined
Mar 8, 2010
Messages
353
Re: Hard Starting when warm

Worn or broken piston rings would cause excessive blow by.Time for a compression check and leak down...Does it idle good?Did your engine by chance backfire and maybe blow the power valve?
 

dobler5

Seaman Apprentice
Joined
Apr 13, 2010
Messages
31
Re: Hard Starting when warm

Yes the engine idles very nice, that is why I am confused. How can I check if the power valve is bad or not? Will do compression test soon. and get back
 

CobiaXL

Banned
Joined
Mar 8, 2010
Messages
353
Re: Hard Starting when warm

TEST: At idle turn your idle mixture screws
(found on the side of the metering block) all the way in. If your
engine dies the power valve is not blown.
 

dobler5

Seaman Apprentice
Joined
Apr 13, 2010
Messages
31
Re: Hard Starting when warm

Ok so here is an update. I turned the idle mixture screws all the way in and the engine DID die. So whew one less issue to worry about. After doing that test I checked my timing and found an issue that concerned me here. My timing was correct but what I was noticing was that the line for the timing was bouncing around every so often. It would bounce to either before or after TDC every so often. Would not be consistently at -4 where the my timing should be. What is the cause of this and could this be my problem?
 
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