I'm hoping someone might have an idea what the deal is. I have a 1985 H34 with a Yanmar 3 cylinder. I think it's 23 HP. I generally let the engine run while day sailing. About an hour or so out on Saturday the alarm went off. The middle light was on on the display/control panel in the cockpit where the key and shutoff are located. I shut it down and sailed the rest of the day without it. It started right up when I went to put it back in the slip. I think it ran about 15 minutes or so before the alarm went off again. The coolant overflow had plenty of fluid in it. I thought it was discharging water from the stern as it's supposed to but that bubbling sound that comes up through the cockpit drains did sound different, more pronounced. Thanks for your input.
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Not sure what signal lite you got on your panel but...
things to check-
check your water strainer for eel grass or other flotsam.
See that you are actually spilling coolant from the aft end exhaust openings
check that your "internal" coolant system has enough antifreeze
Check that your water pump belt is adequately tight and not slipping as it gets hot from friction.
check that your air intake filter hasn't given out and parts of it starving/restricting airflow to the cyls.
Have a replacement water impeller pump "gasket" available and take the cover off the raw water impeller and inspect the condition of the impeller...are the impeller fins there or partially eaten up- time to replace it. You don't want those little pieces going into the system.
Miight want to check out the status/functionality of the thermostat to ensure its opening adequately and at proper temp. Depending upon how old it is- easier to just replace it.
It seemed like the engine starts ...runs a while ...ges hot... alarm ...turn off...let cool... start cycle over again. Thing that gets me was that it ran 15 min. before getting too hot- I would figure the alarm sooner if you had not freshwater getting thru. So I think your impeller is perhaps crapping out and not delivering enough water to the system.
things to check-
check your water strainer for eel grass or other flotsam.
See that you are actually spilling coolant from the aft end exhaust openings
check that your "internal" coolant system has enough antifreeze
Check that your water pump belt is adequately tight and not slipping as it gets hot from friction.
check that your air intake filter hasn't given out and parts of it starving/restricting airflow to the cyls.
Have a replacement water impeller pump "gasket" available and take the cover off the raw water impeller and inspect the condition of the impeller...are the impeller fins there or partially eaten up- time to replace it. You don't want those little pieces going into the system.
Miight want to check out the status/functionality of the thermostat to ensure its opening adequately and at proper temp. Depending upon how old it is- easier to just replace it.
It seemed like the engine starts ...runs a while ...ges hot... alarm ...turn off...let cool... start cycle over again. Thing that gets me was that it ran 15 min. before getting too hot- I would figure the alarm sooner if you had not freshwater getting thru. So I think your impeller is perhaps crapping out and not delivering enough water to the system.
jtmcue has it right. I had the same symptoms on my '94 Ygm 18 hp. It was the strainer loaded with "stuff." Cleaned it and haven't had a problem since.
I have the same engine, Mike. Agreeing with jtmccue and Bruce, and in order.. make sure both belts, the raw water pump belt at the bottom starboard side of the front of the engine and the fresh water pump belt and alternator belt.. the big one.. are both pretty tight. (Thumb pressure deflects the belt about ¼” in the longest run) Raw water pump impeller condition; make sure too that it isn’t slipping on its drive shaft as was mentioned in a previous thread here.. Sea water strainer should be clean. remove the top and pull the screen .. a new top cover gasket is a great idea when ya put the clean screen back in. Hook a water hose to the seawater pump intake hose (after removing it) and blow backwards out the water intake to clear anything from the under-hull inlet..Next, with a cool engine, remove the radiator cap on top of the heat exchanger housing and check that there is not an air bubble in there that would be caused by a problem in the coolant reservoir.. Look for crud in the coolant/water in the heatex housing. If someone thought he was doing good by putting in non-toxic, long life antifreeze, he could have made a mess for you, since it can degrade and cause some serious flaking and fouling! Next, make sure the exhaust elbow is clear and water can flow through. Removing it is the only way it can be checked. If none of this helps then think about the thermostat, but that is a little uncommon.(often suspected, rarely really at fault) Next is to pull the heat exchanger bundle and make sure it is clean. Have the new o-rings and cover seals on hand before pulling it, because the old ones probably will not be re-usable. .
Watching flow out of the exhaust on a 34 is almost impossible because the outlet is right at the waterline under the stern overhang.. As soon as the boat starts moving, the outlet is immersed by the stern’s squatting. At rest, you can’t see it, since it is only an inch or so above the water and invisible from the cockpit, or anywhere except down the swim ladder
Watching flow out of the exhaust on a 34 is almost impossible because the outlet is right at the waterline under the stern overhang.. As soon as the boat starts moving, the outlet is immersed by the stern’s squatting. At rest, you can’t see it, since it is only an inch or so above the water and invisible from the cockpit, or anywhere except down the swim ladder
Mike: If you find out that your strainer is the problem, be sure to check the impeller. Once they get starved of cooling water, the impeller "can" get warm and blades will break off.
This is also a good time to check your mixing elbow if you have never done it, but I would start with the other end first.
This is also a good time to check your mixing elbow if you have never done it, but I would start with the other end first.
BTW- I should have mentioned the heat exchanger- I've pulled mine out once sofar. Have some longish pipe cleaners to ram rod the tubes after you soak it - I think I might have used CRL to desalt the internals of the exchanger. Yes you will need 2 new end gaskets ( I think mine were gaskets but could have been O-rings) for reinstall. On the elbow- thats the last think I'd like to mess with -so unless you run it only a short while and at slow speeds, I doubt you are "coked up".
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