Marinette Boat Forum

have 318 fresh water cooled that runs too hot. Changed all impellers . I am loosing a little antifreeze each time I go out . no water in oil. How do I tell if exhaust manifold (log type) is leaking w/o taking it off?
Thanks guys.
Wayne

Seems I remember Fastjeff mentioning that overheating might be caused by blocked passages in the exhaust manifold. Only recourse was to pull them and "rodding them out". Cleaned out the scale and blockages.

Have you taken an infrared shot of differing parts of the exhaust system? Spikes in temp could tell you where a blockage might be.

Bill

Thanks Bill, I have used infrared gun but no hot spots.
Wayne

How old are the coolant lines? Are the hose clamps tight? Did you clean the clamping surfaces prior to reinstalling the coolant lines?

Air in the coolant lines can cause overheating.

You can check the system for leaks using coolant system pressure tester. Might save you from disassembling the entire system.

Eric

Also look for an air leak before the raw water pump. (A tiny air leak will cause a surprising loss of cooling.) Check the seal on the separator, the hose clamps after it, etc.

Jeff