When I rep[laced my water heater, the first time I ran the engine, it overheated until I added water/antifreeze to the heart exchanger. Make sure your heat exchanger is topped off. Also, there is a valve that adjusts the amount of hot water that's diverted to the hot water heater. If too much is diverted, it can cause the engine to overheat. A clogged heat exchanger can also cause the overheating problem.
I replaced my mixing elbow, last year, when I found a pin hole in it. When I removed the elbow, it practically fell apart (rusted). Heating the elbow and the piece that attaches to the manifold with a torch, and trying to separate the two pieces with a six foot wrench couldn't budge them. I finally replaced both pieces. At the same time I replaced the exhaust hoses. The cast iron elbow lasted thirty years. No need for you to use stainless. Alan Bergen 35 Mk III Thirsty Rose City YC Portland, OR We are on our first extended cruise of the year for a club event in Olympia WA and are hiving a problem with overheating with our 3HM35 Yanmar. Here's the deal... We usually run as about 26-2800 RPM. Depending on the condition of the bottom and the prop, that gives us between 6.5-7.3 KTS. We have had some intermittent issues with overheating, but it was usually me pushing too hard in heavy seas or running above the usual RPM range. Backing off always relieved the problem. And we have no gauge, so this is all based on the alarm which may or may not be accurate. As we were heading out this time the Admiral was at the helm and I was below messing with something and the alarm went off as we were running at about 2200 RPM. We were able to run at under 2000, but above that the alarm sounded and we had to back down. We continued on at 4.5 KTS. I checked the strainer and through hull. All good there. Water seems to be exiting the exhaust as usual. I am planning on a haul out and bottom job next month, and did not have a diver clean the bottom and prop (should have done that for sure). My assumption was that the barnacles on the prop and dirty bottom, along with the 15-20 KT head wind were taxing the engine and causing the overheating. But the "experts" in my club feel otherwise. I tried to get at the gooseneck to see if that might be the problem. I was able to get the water hose off and poke around in there with a wire, but decided that pulling the exhaust hose was not something to try 30 miles from home as if I screwed it up and damages the exhaust hose I could be stuck here for a while. I have heard all of the problem YANMAR's have with exhaust back up and am wondering if that may actually be the problem. I have asked to have it checked every tine I get the engine serviced, but there's no telling what that entailed or even if it was done....so, when she goes into the yard for the pain job I think replacing the gooseneck with the stainless aftermarket one may be in order. Here are my questions: 1. Can the dirty bottom and barnacle encrusted prop- result in an overheating problem? 2. Would a carboned up gooseneck cause a problem like the one I am experiencing? 3. Where can I get one of those nifty aftermarket stainless goosenecks? Any additional suggestions are welcome and appreciated! thx Tom B
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