Trojan Boat Forum

Trying to get an opinion. I have what appears to be a white smoke at idle 500 rpm in my 1976 Chrysler 318. I believe it smells like gas. Once I throttle up the smell and smoke disappear. I am thinking that my carb is running rich at idle and could use a tune up.

Thoughts.

Thanks,

John

White smoke in the exh. usually indicateds a water leak into the combustion chamber.
Best do a pressure test on the cooling system, this will let you know if you do have a leak in the system.
Also if you have been adding water to the system as of late this is also a good indication of a leak.

blackish means gas [or so I thought... it's not oil?]. personally,if my boat sits for a few days,the ports engine is a little harder to start fron oil leaking down the valve stem[s ]in the pot[s?] due to 30 + year old valve seals....a getaround to it job.

white smoke can be unburned fuel Is the engine missing ?

The boat doesn't miss but does run a little rough at the 500 rpm. Are you thinking a carb rebuild in the offseason

I would get someone to look at it , to diagnose it over the net is little better then guessing . If i could look at it I could mostly tell you right away .

My 318 runs like a top but "hates" under 600 rpm. 500 is sort of low IMO for any type of smooth running. When mine sit for a while (a week or more), it does smoke at low idle, especially when first started. But this clears up under way. We're not talking WWII smoke screen here, but it does smell more like rich mixture than burning oil. The smoke is light blue, not white, however. When I start up I let it run between 800 - 1000 rpm for a couple of minutes just to get it warmed up. I'm on a upstate NY lake and the boat is raw water cooled so the engine is cold starting and running for the first few minutes.

For what it's worth, Chrysler Marine Engine manual from '79 recommends idle speed of 600-700 RPM in gear. Personally I find that's about as low as I would ever want it, as lower than that I don't get enough power to the props for close quarters maneuvering. I usually set up for about 700-750 RPM in gear.

Mine used to do that, after I fixed the timing issues and installed a new carburetor it no longer does that.