Yanmar raw water cooling

[Bill22113]

Not getting water out the exhaust when engine (2QM15 - raw water cooled)warms up.Was pumping plain water fine when cold (from a bucket - boat is "on the hard")and then I started running antifreeze and the flow stopped and the engine temp warning light came on. Water (and antifreeze)does seem to be getting to the block (plenty drains out when I disconnect the inlet hose). New thermostat had no effect. Is this an exhaust manifold jacket clog, an impeller that's too weak to pump antifreeze (but can pump water!) or something else? Because water is going out the mixer elbow when cold, can't be a clog there.

 

[Robert]

Cooling problem

I don't know the 2QM15, but the only time I've had water flow problems with my 2GM, it was the raw water pump belt slipping. This was non obvious and took me quite a while, including disassembly of the pump!, to diagnose. The thermostat shouldn't be the problem, since it has a bypass hole so water should flow whether the engine is cold or hot, just less when cold. I don't think the viscosity of the antifreeze (hopefully you are using the "pink" nontoxic kind) is different enough from water to make a difference to the pump. I'm assuming you don't have a heat exchanger to make engine hot water on the boat, but if you do then you have two independent fluid systems on the engine.Good luck,Robert