Engine running HOT! Need advice.

[apollo24]

Took X-18 out this weekend. Thermostat started jumping around a little, then it went through the roof as I smoked a big Fountain at a bend in the river. :)

I immediately shut it down and got towed by a bassboat.

Reckon it's a stuck thermostat or a bad impeller in the pump (the pulley was spinning).

The risers were HOT!

[harbormaster]

I don't prfess to be an expert but since you ran the Tstat hot, its not a bad idea to go ahead and replace it.
I would check out your impellor. If its been over year or so since it was last changed its definitely a candidate.

[MOP]

Scot is 100% right, T stats are cheap. Question how long were you running before the OH? Have you checked to see if any water got into the oil? It is a good idea to do a compression check not that it will rule out a possible leak but will show a bad one. With an over heat it is always good to start at the source, you say belts were spinning so I am guessing you are running an inboard pump. If you have an oil cooler before the pump start there, pull the hose to the cooler and to the pump completely off. Check cooler for debris, carefully check hoses to see if inner liner has come loose, it can collapse and choke off feed. I did put all this before the so it does in fact get checked, Not sure which style pump but tear into it, that may be the full cause of the problem but at least you will be good to there. Fire it up check for good flow should be fine, you still may not be out of the woods. Bring the RPM up to about 2500 to build pressure within the block watch the seams where the heads meet the block by the spark plugs to see it you have any seepage. Once it reaches op temp shut it down and let it cool off and recheck the oil for water, all this stuff does take time but worth it. If everything looks to be OK another thing that is worth checking is an air leak coming from the drive while underway, to do this get a long piece of clear hose the right size to fit between the transom and the pump. I like it long enough to be able to drape it out into the cockpit so I can see the water flow a various RPM ranges (don't forget to secure the hatch from blowing open). Normally drive will let air into the cooling water as they go on plane, I have seen Volvos suck air only at WOT. Hope some of this helps.

Phil

[apollo24]

WOW!

Thanks, guys. I need to print this out and head over to the boat for a few hours!

What should I tell my boss? :)

Ben

[apollo24]

Don't scare me with that WATER IN OIL STUFF.

All of a sudden, she started running hot. Ran to the stern, and water was barely trickling out of the thru-hull exhausts. Engine ran funny for a minute right before that when I was chasing down the Fountain.

Then checked external belt driven water pump. It WAS turning. Could it still be that the impeller is worn?

[Morgan's Cloud]

Don't overlook the possibility that you could have had a plastic bag etc. wrap around the lower unit temporarily. Nothing will cook an engine faster ... especially if your running at full tilt.

S

[harbormaster]

Impellor could have failed and then you would be pumping hardly anything.

[tmdog]

I would'nt bet the farm on it but I think your exh. risers are plugged (rusted over. First thing pull the risers and check the ports. If plugged, use your cordless drill and proper size bit to open up.

[MOP]

Another quick check to see how the flow is through the engine without pulling everything apart. is to pull the hose coming from the pump to the engine and run the garden hose to it. If it flow free the problem is before the pump.

Gues you will be a busy camper this weekend!

Phil