A LITTLE HELP from my friends?

[Dragon Fly]

Here's the symptoms:
the 10 h.p. diesel in my 1984 Oday 28' over heats , quickly according to the gauge in the cockpit, even at slow idle. Then.. if like a miracle,
it drops down to 100* from around 200* or so and seems fine.

trouble shooting:
a. sanded the contacts clean on the sending unit on the engine.
b. made sure there is antifreeze flowing thru the hot water heater hoses
c. noticed adequate water belching out of the exhaust at the stern
My guess:
1. the gauge is bad
2. the sending unit is bad
3. the thermostat sticks?
recommendations:

any you Oday 28 sailors got an opinion, or been thru this before me?

 

[Don S/V ILLusion]

when was the last time you changed the thermostat?

If it's been a year or more, it's overdue

 

[Tom Potter]

There are a few other things you can check. There should be a little petcock valve on top of the thermostat housing. This valve is used to bled the air out of your cooling system. It's very important that all the air is out. Air locks in the cooling system can generate issues as you describe. I recently had to bled the air out of mine and it took several attempts. I bled it while the engine was running, I ran the RPMs up then let it idle, cracked open the valve and air would come out. Did this several times until no more air came out.

Also your heat exchanger may need to be cleaned. I pulled mine off a couple weeks ago and took it apart. Several of the tubes were stopped up. You could take it to a radiator shop and have it serviced for you. I chose to do it myself. The zinc end of my 2" exchanger had a bunch of old worn broken pieces of zinc. I shook and shook and got them out, they came out the small hole the zinc goes in. I then took a piece of small cable and ran it back and forth in each tube until each one was clear (disclaimer you could cause damage to your exchanger if your not careful). After I finished the tubes, I let it soak in a CLR bath for about 15 minutes, then rinsed it very good. I was very pleased with how clean I got it. You will need to get a replacement gasket for the exchanger end plate.

 

[jibes138]

Not sure a new thermostat is required once a year? You certainly don't do that in a car and this is the same sealed environment. You can easily test your thermostat. Pull it out and put it in a pan of water on the stove. Water boils at 212 so it should be fully open since I think it is a likely a 160 degree thermostat.
It is really tough to get all the air out. I put a hoes on the upper wot water heater connection, held it higher than the coolant tank and then filled it until coolant flowed out the cap. Run it with the cap off and crank up the RPM's a bit, you should see the coolant circulating in the tank once the thermostat opens, also the level will drop a little if you get air out of the system. I also pulled my thermostat and poured coolant down the passage to make sure that cavity was filled. Also do as Tom suggested. IN NO CASE LET IT OVERHEAT GOING OVER 200, shut it down immediately. I had exact same problem with my heat exchanger, all kinds of zinc pieces to snake out.

 

[JK_Boston_Catalina310]

A couple of my thoughts.

1. Thermostats should not need to be changed annually.

2. Your heat exchanger should be cleaned regularly. How often depends on how much you use your boat. Go to the Musings of Mainesail forum and look for heat exchanger cleaning discussions and google Compass Marine How To Articles (Mainesail's personal site) and read about cleaning the heat exchanger. You don't have to be overly handy to do that job.

3. While on the Compass Marine site, read how to take temp readings with an infrared thermometer. I bought mine for $35 at Lowes. This will tell you if you gauge is right.

4. I bought a cheap 22 rifle cleaning kit from BassPro for periodic (annual or more often depending on how much we motor) cleaning.

5. If the engine is really overheating, definitely check if you are air bound as suggested above.

6. Do you have a slotted cover on your raw water intake? If you do check it. You could have growth partly blocking the intake.

Hope this helps.

Jesse

 

[Stu Jackson]

Engine Overheating 101 - How to Burp Your Engine (Reply #6) http://c34.org/bbs/index.php/topic,4518.msg26462.html#msg26462

You don't have to take the thermostat off to burp your engine.

 

[Don S/V ILLusion]

1. Thermostats should not need to be changed annually.

Although he didn't confirm, a 10 hp diesel is likely raw water cooled meaning the thermostat is sitting in salt water constantly.

Someone else suggested - "You certainly don't do that [replace annually] in a car and this is the same sealed environment."-

cars don't run salt water cooling...

 

[jibes138]

OP noted he added anti-freeze to the water heater, this suggests thermostat is in an anti-freeze environment. Your point about raw water is well taken if it was raw water cooled I could see the thermostat having troubles.

 

[Davidasailor26]

Agree that the thermostat should not need replacing every year. Ours is original from '85 and doing fine. Our engine is a 10hp universal m-12 and is fresh water cooled. From the OP it sounds like his 84 is the same. I do agree with the recommendations to check the heat exchanger for clogs. Also, from the symptoms that that the engine rises to 200 then drops and runs fine, it does sound possible that the thermostat could be the culprit in this case. I'm thinking it might be possible that the thermostat is sticking and just not opening until 200, but then opens and everything's good.

 

[Dragon Fly]

thanks 4 replies
i replaced the temp sending unit on the block.
removed the thermostat.
installed a new heat guage in the cockpit.
Made sure antifreeze was full up, in on the engine and in the hoses
connecting to the hotwater heater.(trying to ensure there's no air lock in the line.)
Took her off the mooring today, for a little sail. Engine overheated above 200*!!~!
Ps: the heat exchanger was just replaced(new) by the former owner at a large expense like $600.
so now what guys? i'm out of ideas.

 

[Dragon Fly]

over heating universal 10 h.p. oday 28

thanks for the opinions and advice guys.
I'll attempt the bleeder petcock idea on the top of the engine;
i'll take the top off the hot water heater and see if i can detect air in the lines.
i'm thinking perhaps the hot water heater could be taken out of line altogether?
what ever this is... it a sorry september sailing month so far!
any other thoughts or advice, come back with it to me
many thanks
dragon fly

 

[SEMPERAVANTI41]

1. Replace the raw water pump impeller. I had one once that worked on & off.
2. Replace & tension fan belt.
3. If problem not solved, I would remove water pump & inspect/replace.

 

[Dragon Fly]

BURPING duh Oday 28

great article ! thanks !
Engine Overheating 101 - How to Burp Your Engine (Reply #6) http://c34.org/bbs/index.php/topic,4....html#msg26462

i'll try taking that hose off as instructed and will let all you helpful guys know how it goes
greatful

dragon fly

 

[jibes138]

If you are getting good raw water flow out of the exhaust then it probably isn't the raw water pump, raw water intake or heat exchanger. I would still suspect an air lock especially as it relates to the hot water heater loop. Put a piece of hose on the top hose connection to the hot water heater and hold it above the level of the coolant tank. Fill it with 50% anti freeze mix until coolant come out the filler cap on the coolant tank. Take the hose that normally goes to the hot water heater and fill it and then quickly put it back on the fitting and clamp it. The hot water heater should now be full of coolant. This did the trick with mine when I had repeated overheating like you are experiencing. You can also try running with no thermostat but it will run cold, as noted try checking the thermostat in hot water to make sure it opens. Simple check of good/bad. Another possibility is a bad fresh water pump but those usually make a lot of noise when they go bad.

 

[anchorclanker]

While you dont need to replace the T stat annually, they do fail. While the situation could have other causes, the observation you've witnessed is a typical symptom of a dying T stat and thats where I would start.

If its over 4 years old I would just replace it and check it off the list. You can check them in a pan of water on the stove with a thermometer, but I dont bother testing them anymore as after a few dozen times it seems more inconclusive. I cant count the times they looked like they were working okay on the stove but still ended up replacing them anyway because they simply wernt working right. Once youve gone to the hassle of pulling it, just replace it and dont look back. After you swap it, try running it and see if the problem went away. If not, at least you know its not the stat. Then you can save the old one in a box as a spare aboard the boat.