Marinette Boat Forum

One of my twin 318's has a very strong rust discharge when starting it. The other one does not. After a minute or so, it clears up. The engines have about 1900 hours on them and seem to run good and smooth. Is this discharge a problem? What could it be from?

Thanks in advance for any answers.
Capn Gary
1986 32 FB
twin 318'a,
Milton, Fl

Guessing you have raw water cooling and it is rust from inside the block. Watch the temperature and oil in both engines. The other engine will have some rust too, you don't want it to clog the oil cooler or internal passages. The rust was cast iron that was your block or manifold. When they rust out you can get water in the oil.

Rust discharge not confined to raw water engines. I had it almost every time I started up after a rest interval of, say, a week between boat outings. Closed cooling system. I had '88 32' FBS w/240's. As gary noted, it cleared up quickly. Always concerned me but I suspect it was quite normal but I do confess being surprised more folks on the forum aren't talking about it.

Even with closed cooling the exhaust manifolds and any exhaust fittings you may have, have raw water flowing through them. So it is normal to get some rust from them. My manifolds lasted ten years.

Good thoughts, thanks,
They are raw water cooled. In brackish water this past one year. In freshwater the rest of it's prior life. I did install flushouts and use them every time the boat is returned to dock to make sure freshwater is in the system. Temp and oil have been OK so far.
Capn Gary