Temporary overheating

[Don Sargeant]

So I'm pooping along at about 2,000 RPM and showing 180 on the temp guage (CD25D, Westerbeke 2/10, 208 hrs.), but I've got a way to go so I step it up to 25-2600. The temp needle goes off the dial! I throttled back to about 1600 and the temp dropped back down to 180 and stayed there when I went back up to 2000 rpm. Being there was no wind at all, I didn't press my luck to throttle it up to 2500 again. Other than the chance something blocked the intake temporarily, what else may have happened. The exhaust outlet is under water when we're underway, but it looked like it was pumping. I hadn't run the engine over 2000 up to this point, so I was shocked to say the least.



don@cliggott.com

[Steve Alarcon]

Don,

Sound like you have some buildup in your lines/hoses. There is enough flow to take care of normal load, but not "stress". Check the low points.

Steve Alarcon
CD30 Temerity
Seattle



steve.alarcon@attws.com

[Sam]

I would check the thermostat. It's probably stuck.

[Lee H. Hodsdon]

Don,

I had the same problem with the same engine. This is what I did. I changed the raw water impeller as one of the vanes had a small crack at its base. I cleaned out the heat exchanger passages with a stiff piece of copper wire. The heat exchanger is accesed from the port cockpit locker. You will see a 2" diameter cylinder just above and behind the starter. The cover is attached with one bolt, and has a rubber gasket to prevent leakage. Close the raw water seacock, and loosen this cover. There are maybe 6 to 8 passages from the port side of the heat exchanger to the starboard side. I ran the wire in and out of each of these passages. I found some eel grass, seaweed and the like. I put a thin coat of grease on the gasket before replacing and securring the cover.

I checked the belt tension for the alternator/raw water pump and found it loose. My assumption was there may be slippage at higher revs. Do not overtighten the belt.

I added a raw water strainer to the inlet hose and removed the external screen attached to the hull at the intake.

Finally I rebuilt the raw water pump, replacing both bearings and the seals. This seems to have corrected the problem. I have not had overheating problems for the past 2 seasons. I did not check the thermostat, but I will. That seems like a great idea, kind of embarassed I didn't think of it.

I also replaced the doughnut type zinc with a Perry Nut, this seems to have improved the flow of water over the prop, and reduced drag and or cavitation at higher rpm's, both of which may have increased the load on the engine and caused overheating.

Sincerely,

Lee

So I'm pooping along at about 2,000 RPM and showing 180 on the temp guage (CD25D, Westerbeke 2/10, 208 hrs.), but I've got a way to go so I step it up to 25-2600. The temp needle goes off the dial! I throttled back to about 1600 and the temp dropped back down to 180 and stayed there when I went back up to 2000 rpm. Being there was no wind at all, I didn't press my luck to throttle it up to 2500 again. Other than the chance something blocked the intake temporarily, what else may have happened. The exhaust outlet is under water when we're underway, but it looked like it was pumping. I hadn't run the engine over 2000 up to this point, so I was shocked to say the least.

lhodsdon@nh.ultranet.com

[gates_cliff]

When I put my boat back in the water this spring, it started right up and I motored to my slip. I had had it winterized by the local shop at my marina and asked if there was anything I should do when going back in the water. The mechanic said nothing really just make sure there was coolant, which I did. I wasn't able to use my boat much this spring but had motored out of the marina a couple of times and back in.

Then about a week ago I realized I needed to fill the fuel tank, the fuel dock is about 20 yards from my slip. So, I went over, but had to wait a couple of minutes for a power boat to leave. While waiting the overheat alarm went off. I had water coming out of the exhaust likes it's supposed to. I went ahead to the fuel dock, shut it down, filled the tank and started back up, the alarm is still on. Since it's just a short distance I motor back, total time is maybe 5-7 minutes with overheat alarm going off. I check everything that I can and don't see anything alarming, water still coming out of the exhaust. Finally checked the small coolant reservoir and see that it's nearly empty. I talk with the mechanic and he gives me some coolant and I fill the reservoir up. Run the engine for awhile and it seems fine.

So 2 days ago, one of the few days when the heat and humidity weren't oppressive. So I decide to go out. Leave my slip, get out of the marina which only takes 5 minutes tops, and sure enough the overheat alarm is going off. I decide to go ahead and sail for awhile. So sail across the bay and back, get back near the marina furl the sails and start the engine to get back to my slip, fully expecting to hear the overheat alarm...but it doesn't go off! Nonetheless, get back in and again only run the engine no more than 5 minutes.

Go back yesterday to try and investigate and find the reservoir is empty. So just out of curiosity, I start the engine and there's no heat alarm. The engine temp is showing 180, which is typical. I sit there for 20 minutes with engine running at idle then rev it up to about 1500 RPM and run it for another 5 minutes.

No overheat alarm and the temp gauge never went over 180.

After perusing this thread I'm wondering if maybe there was something in the heat exchanger that eventually got expelled which allowed the engine to run ok. I don't want to damage the engine but am stumped as to what this might mean.

Sorry for running on, but wanted to give context.

[Joe Myerson]

I had a similar problem with my 1GM. It turned out to be some seaweed that got sucked up through the raw-water intake. I couldn't find it, but the yard removed it. This could be a possibility, as well as all the other possibilities.

--Joe