Engine hot idiot light came on

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Chris Mead

The other day after running the Yanmar GM for about an hour back to port at around 2000 RPM...nothing unusual...the hot-engine warning light came on. Checked the raw water strainer -- not blocked or anything. Have enough anti-freeze. Tonight I'm going to pop off the impeller behind the belt. Question is...any other thoughts? Anyone ever have the idiot lights conk out? Where is the thermostat?
 
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Miles

Could be the thermostat...

Or sometimes something will block the raw water intake on the outside of the hull and prevent water from getting through. Was any water coming out when the engine overheated?
 
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Paul Akers

Growth in intake

Sometimes creatures (barnacles) take up residence in the intake thru-hull which is hard to reach with bottom paint and restrict full intake of water.
 
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Brian Smith

Cold water cooling light

I had the same problem on my Hunter 31. The thermostat was the problem. Not difficult to change at all. On my 2GMF it's on the top of the engine. Takes about 10 minutes to replace. Good luck.
 
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Mike

Seacock

If you have the old gate style seacocks, the gate could have corroded off the shaft in the closed position. Take the hose off at the seacock and if water flows then you know the problem is closer to the engine. If you do have gate seacocks and it's not the problem...put them on your list of things to replace next off-season.
 
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Bill O'Donovan

Two more things

Check to make sure the L-shaped hose for raw water intake is really L-shaped and not just bent. Any auto parts store can fit you with the right one. 2000 is pretty low rpm's and may be contributing to the overheating. 2800-3000 is recommended.
 
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Dave Winiker

Idiot Light

Two faults which recently caused the engine overheat idiot light and alarm (really obnoxious) to activate are: restricted raw water flow through the heat exchanger caused by an old impeller vane restricting the flow of raw water through the exchanger and secondly a busted raw water pump belt. We shut down the engine each time and sailed back to the vicinity of marina before restarting the engine for docking. (I'm not quite to the point where I can back into the slip under sail.) Both fixes were relatively simple and the heat exchanger tubes were in good shape.
 
Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
No barnies, but what about the ZBras

Chris: You probably don't have too many barnacles in Lake Erie, but do you have Zebra Mussels (or what ever they call them up there?). If you do not want to get in the water, consider getting a stiff piece of wire or something the you can poke down from the inside of the open valve on the seawater intake. Be sure that you are getting good flow. If this is clear then you need to just check everything out from the seacock to the mixing elbow. You should not be cruising at that low of an RPM like Bill O mentioned. You should be cruising at a minimum of 2500 up to about 3000 rpms as your cruising RPM. Once you know that everything on the raw water side is clean and clear then you need to check out the fresh water side. Don't forget belts, impellers, heat exchanger, check for soft hoses (they can collapse under suction).
 
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Chris Mead

Impeller is just fine

Thanks for the thoughts so far. The impeller is fine...but...I think the problem was air. The water pump intake hose was loose. So I replaced the impeller, tightened all the hoses. Then..I read that I should have greased the impeller housing. Any thoughts on that? I also think I'm going to replace the thermostat. Cheap and easy enough.
 
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Jim A

Check your intake hose

I had a piece of grass with a wierd root clogging my intake hose. Look just before the strainer. The inside diameter of the water path is restructed because of the strainer fitting. I was a bitch to find! Jim, DownTime H28
 
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Doug T.

Thermostat

I was out one day motoring merrily along when the warning buzzer went off. (Well, not so merrily... there was no wind and I'd rather be sailing...) Anyway, after working my way through the cooling system from the intake to the strainer to the impeller to the thermostat, I found that the thermostat was just about welded shut. Total junk. Luckily there was a spare on board (this was a new-to-us boat). Put it in and all is great. Check out yours. Replace if necessary and stock a spare one under a settee somewhere...
 
Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Good Idea Doug.

Doug: I think that saving the old parts (belts, hoses, impellers etc) that are still in workable condition is a very good idea. You never know when a part is going to fail (new parts fail too). If you are doing prudent preventative maintenance, many of the old parts will still have some life left in them. Get an old plastic box and save these old part for the ultimate failure.
 
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Crazy Dave Condon

what year is your boat

What model year is your boat. Crazya Dave Condon
 
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Matthew Jenkins

Engine overheating - try mixing elbow

Sounds like you're on the right track. The first thing to check is the strainer. Even if it is clear, the through-hull may be clogged by a plastic bag or something. disconnect the intake hose by the strainer. Open the seacock (slowly / carefully). If you get a spurt of water, it's clear and this option is eliminated. Next step is to change the impeller. It's easiest just to disconnect the entire water pump assembly and change the impeller while seated at a table. When you're done just re-attach the whole water pump. This is a good time to change the belt too. (Quick job, fairly easy. It's nice to have 2 people when re-attaching - one to hold the pump / tension the belt, and the second to tighten the nut.) Chances are your impeller will be fine and the problem is the mixing elbow. This is the third thing to check. This metal horseshoe shaped piece rises out of the top back of the engine near the heat exchanger. It's where the water is mixed with the exhaust to be exited. After about 10 years it gets gunked up and corroded inside, eventually blocking water flow. It may be possible to clean the one you have. It may need to be replaced. This happens eventually to all Yanmar 2GMs. Depending on your skill with diesels, this may be something to have a mechanic do. Good luck. Matt Jenkins s/v Moondance cblights@earthlink.net
 
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Jim A

Chris, the mech. at the marina told me

that if the engine has been over heated and you are using green anti-freeze is makes a film. If this has happen he says to acid wash cooler and clean the back of the heat sensor real good. Jim, DownTime H28
 
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