Mercruiser Breather Tube

[boatingedge]

I was going through the process of adjusting my carb idle mixture screws and after the engine had warmed up I noticed very light white smoke coming from the breather tubes. I could only see the smoke when a flashlight was shined directly over the carb so it is not a heavy thick smoke but a very light almost clear smoke. When I got back to the dock I removed the plugs and they were all fouled which is not suprising since I beleive the carb needs to be rebuilt due to constantly fouling the plugs. I also checked the compression and all cylinders were within 10% of each other.
The engine sounded fine and starts up with no problem. So my question is what is the smoke that is coming out of the breather tubes? Is this normal?

Engine is a 1996 Mercruiser 7.4L 300hp.

Thanks as always for your advice.

 

[Don S]

Re: Mercruiser Breather Tube

Some smoke/steam is normal.
Did you have the Thunderbolt V ignition in base timing mode when you adjusted the idle mixture? You are supposed to.

 

[boatingedge]

Re: Mercruiser Breather Tube

Yes I did have the ignition in base timing mode. Thanks for your help Don.