1999 Merc 135hp huge smoke

Gentlemen, did a search and didn't find anything so here goes. I have the above described engine which really smokes alot when I start it. I mean huge smoke! It is truly embarassing. It is kind of hard to start initially and then the smoke begins. After it warms up the smoke goes away on re-starts. I use this boat about once or twice a month in the summer. It runs good, etc. Would the fuel pump diaphram cause this? I have a feeling it has never been replaced, I know I haven't. Thanks for any suggestions.

Re: 1999 Merc 135hp huge smoke

A short answer is that possibly the Crankcase pressure one-way check valve on the oil injection system is faulty and is either causing too much pressure to be built up in the system or is not releasing the pressure from the sytem in a timely manner after the motor is shut down. Either failure can cause oil to be pushed backwards into the fuel line while the motor is off, resulting in a fuel mixture with too much oil being sent to the carbs the next time the motor is started. Once this extra oil rich mixture is burned off while running the motor, the motor stops smoking. I had this problem myself once so I know how this can happen and the solution. A much, much longer and more detailed answer can be found in the following thread:

http://forums.iboats.com/showthread.php?t=182406&highlight=smoke

I have heard that a fuel pump with a failed diaphram can leak fuel into a cylinder causing smoke at startup. I have never had this happen to me but I can imagine that such a failure would also cause poor idle. If the motor idles fine, then I would not think this is not the likely problem.

Re: 1999 Merc 135hp huge smoke

Thank you sir.

Re: 1999 Merc 135hp huge smoke

Upon reading the posts, I'm pretty sure the check valve is the problem. I noticed my reserve oil container holds pressure for months. Every time I loosen it there is pressure on the tank. I thought this was normal.......

thanks again for the fine advice.

Lynn Wagoner
Yukon, OK

Re: 1999 Merc 135hp huge smoke

Looks like undoing the oil tank cap to relieve pressure will temporarily fix the problem and would also give you proof positive of the diagnosis.

Might be something to try if you don't get the check valve replaced before your next time out.......ed

Re: 1999 Merc 135hp huge smoke

Emckelvy......that fixed it! Thanks again.