Marinette Boat Forum

Unless some kinda metal bug ate your impeller, I doubt if the circulating pump is the problem. (Their seals leak, that's all.)

Very easy for the strainer gasket--that you think is in there okay--to leak air. I replaced that fool thing with a homemade O-ring made from 3/16 vacuum hose glued together with a wire inserted. Easy to do and it NEVER leaked again.

Jeff

I would take the T-stat out completely. The engine won't heat up as fast but otherwise will be fine. Run it for a while and see if you still have the problem. Often there is nothing wrong, just air trapped in the housing and needs to be bled. With air trapped you have no coolant there, so the t-stat never heats up and opens. Or the t-stat is bad. ( you can drill a small hole in the t-stat to help it by pass some fluid and force any air out )
To check for air leaks on the suction side I would have it running and pour water over each possible leak point. Use a garden hose or a bucket of water. See if it sucks in water where it might be sucking in air.

Thanks for your suggestions! Next time down i will try them, next weekend.

I replaced the thermostat with a new 140 degree stat. In the process i found two impeller tips wedged in the two smaller holes of the housing. Lord knows how long they have been there. I thought that was the problem but nope. No change. The cast housing is very rusty, will replace it with the revised one soon.

That'll do it! Had an impeller grenade on me as well and plug up the starboard side of the system.

Jeff

Tomorrow, new thermostat housing and new thermostat, will install a different washer/gasket on the sea strainer stud, check transmission oil cooler for a restriction, inspect all hoses. Will pull spark plugs to sure its not running lean (i doubt it).

Installed a new engine circulation pump with no change. No engine hot spots and cool exhaust manifols. Clamped the short hose between the circulation pump and the engine and it cooled right down. So there is something keeping the water in the engine at the thermostat housing. It has the new thermostat housing and a new 140 thermostat. Still baffled on whats causing the problem. Still able to cruise and fire up the port motor for docking etc.

Weird! I suggest you individually remove the hoses leaving the T-stat housing and see how much water pours out.

Good luck!

Jeff

Considering trying "Barnacle Buster", let it sit in the engine for four hours and then open the fresh water valve and flushing the engine. It is really meant for salt water closed cooling systems however they do claim rust removal.. It appears i have slight blockage some where in the engine. Will be taking off the intake manifold to inspect it and the water jacket inlets for debris.

Uuugh! Thanks for reminding me why I got out of inboard cruisers.

Jeff