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Volvo MD7A overheating
"hpeer" wrote in message
... Capt. JG wrote: "hpeer" wrote in message ... I have Volvo MD7A, 13 hp two cylinder unit with salt water cooling. Runs perfectly with one exception, it occasionally overheats and I can't figure out what the heck is going on. I bought the boat used and the previous owner had fitter her out himself. Every time she overheats, I find something to "fix" after which she is fine for a spell then she will overheat again. Clearly I'm not getting to the root cause. Generally she will seem to be running along just fine and all of a sudden the pressure gauge just goes up, up, up. It seems to be a bi-state kind of thing, it either works perfectly well or not at all. Its almost as if there is a ball valve or something somewhere that is sticking. It's obviously not a bad gage. The plumbing goes like this: Through hull fitting Salt water strainer Tap to the transmission/engine Tap to secondary pick up from bilge Tap to sinks Here is some of the history and what I had done, in each case I have also checked/changed the impeller. They usually look just perfect. 1: Recently fitted salt water strainer seemed to be blocked with debris from its construction. It is home built out of some interlocking pieces of PVC pipe, the inner piece has a zillion small holes drilled in it. I dumped this stuff out and she was fine. 2: Found a small leak in the copper pipe from the transmission to the impeller. I thought that maybe it was sucking in air and the impeller was getting air bound. Repaired the leak. 3: Moved and lowered the salt water strainer. This was mounted pretty high on a bulkhead with real long hoses. I moved it to the engine compartment and lowered it. I thought that maybe there was just too much suction head to get the water going. 4: Threw thermostat overboard. Any clues? Many thanks, Howard Do you have water flow out the back when it overheats? Is it normal flow? Also, I'm thinking about a failing raw water pump... not the impeller. It's driven by a belt... is the belt snug? No, the engine is not sucking up water. The bilge intake is used when winterizing so that I can put anti-freeze into the engine. The last time this issue/problem occurred was during layup and I was not able to get the engine to suck up anti-freeze. This particular water pump is on a little shaft on the back of the engine. I suppose the pump could be failing to turn intermittently, I had not considered that possibility. Seems kinda far fetched, but then again this whole problem feels weird. Seems like something that intermittent wouldn't be related to restricted flow, since if it's restricted, it's not going to get better. -- "j" ganz @@ www.sailnow.com |
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