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post #1 of 12 Old 10-27-2013 Thread Starter
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Engine Overheating

Hello folks,
I recently purchased my first sailboat - a 1984 Silver Anniversary O'Day 31. She's a beauty and I'm living aboard so we're getting to know one another well. I'm digging into the systems that need attention as they present themselves, and finding my footing on several steep learning curves.

The current priority is an overheating engine, and this is torture because we've had some great wind here in Charleston this week. The Universal 18 began to overheat on my last go-out. There was, and still is, plenty of water coming out of the exhaust. Trying to be sequential in eliminating causes. In sequence I have: had the hull cleaned and checked (good report), pulled the raw water strainer (basket was clean), checked the water pump impeller (solid and clean) and pulled the thermostat (opens and closes in boiling water). Under load (tied to the dock) she's still running hot (shut her down at 200), but at idle she doesn't top 180. Today's project: pull and examine the heat exchanger, then consider my options. Some say clean it myself, other say take it to someone and have them do it. There are plenty of helpful and knowledgeable folks here at the marina, and everyone has an opinion (naturally!). No one has direct experience with an O'Day 31 , however.

Headed into the engine compartment now. Any thoughts on (a) clean the heat exchanger myself and if so, with what, since muriatic acid seems to have pros and cons or take it somewhere? (b) other possible causes of overheating? There is no water in the oil, and the freshwater manifold needed refilling twice during the run in when the engine overheated - never let it go dry, but added about two cups of coolant/water twice.

Thoughts and advice are appreciated!
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post #2 of 12 Old 10-27-2013
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Re: Engine Overheating

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Originally Posted by SeaSky View Post
Hello folks,
I recently purchased my first sailboat - a 1984 Silver Anniversary O'Day 31. She's a beauty and I'm living aboard so we're getting to know one another well. I'm digging into the systems that need attention as they present themselves, and finding my footing on several steep learning curves.

The current priority is an overheating engine, and this is torture because we've had some great wind here in Charleston this week. The Universal 18 began to overheat on my last go-out. There was, and still is, plenty of water coming out of the exhaust. Trying to be sequential in eliminating causes. In sequence I have: had the hull cleaned and checked (good report), pulled the raw water strainer (basket was clean), checked the water pump impeller (solid and clean) and pulled the thermostat (opens and closes in boiling water). Under load (tied to the dock) she's still running hot (shut her down at 200), but at idle she doesn't top 180. Today's project: pull and examine the heat exchanger, then consider my options. Some say clean it myself, other say take it to someone and have them do it. There are plenty of helpful and knowledgeable folks here at the marina, and everyone has an opinion (naturally!). No one has direct experience with an O'Day 31 , however.

Headed into the engine compartment now. Any thoughts on (a) clean the heat exchanger myself and if so, with what, since muriatic acid seems to have pros and cons or take it somewhere? (b) other possible causes of overheating? There is no water in the oil, and the freshwater manifold needed refilling twice during the run in when the engine overheated - never let it go dry, but added about two cups of coolant/water twice.

Thoughts and advice are appreciated!
If you can reasonably easily disconnect the raw water input at the heat exchanger and the tube between the heat exchanger and the injection nozzle at the mixing elbow, and temporarily connect some hoses to the connections, you can recirculate a mixture of RydLyme and water or Barnacle Buster and water through the heat exchanger by connecting the hose on the discharge side of the heat exchanger to a small submersible bilge pump immersed in a bucket filled with either of the above mixtures and powered by jumper cables to the ships batteries. The other hose leads back to the bucket of course. It may take several hours or more to do a thorough job but the materials do work very well. BTDT. I use this method annually to service the heat exchanger in our AC system.

FWIW...

"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."

Last edited by svHyLyte; 10-28-2013 at 09:10 AM. Reason: add addendum
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post #3 of 12 Old 10-27-2013
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Re: Engine Overheating

Sounds like you've tried many of the common possibilities. The loss of coolant from the fresh water circuit is a concern. You shouldn't be loosing any. The reason for this needs to found out. Its possible there is air in the fresh water loop and this is causing the overheating under load.
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post #4 of 12 Old 10-27-2013
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Re: Engine Overheating

I agree with Jim, the loss of coolant needs to be figured out. The fact that you have adequate water out the exhaust indicates that there isn't much restriction in the heat exchanger. Are you getting an abnormal amount of pressure in the coolant reservoir?

John
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post #5 of 12 Old 10-27-2013
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Re: Engine Overheating

A small leak in the heat exchanger can allow coolant from fresh side to go out the raw side when engine reaches temp and pressure. Try easing the pressure cap to test. Overheating (a different issue) may be water pump failure or clogged tubes or failed sender.
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post #6 of 12 Old 10-27-2013
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Re: Engine Overheating

In my opinion you haven't eliminated the thermostat as the culprit. So it opens in boiling water? It should start opening at 175F. The correct test is to place it in a pan with a thermometer, and check that it starts opening at 175, and is fully open by, say 185 to 190F.

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post #7 of 12 Old 10-27-2013
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Engine Overheating

Assuming your heat exchanger is in good shape, it sounds like a leak in the fresh water side of the system. If air is entering the system you will see elevated temperature. You will need to bleed/burp the coolant system. this will also be the cade If you pull the heat exchanger and break into the system.

To bleed:
There is a bleed screw/t-nut on top of the thermostat housing. As strange as this sounds, no need to use it. Instead,

1. Start the engine
2. Wait for thermostat to open (will see temp reading)
3. With transmission in neutral, pump the throttle back and forth between idle and WOT. This will help force air out of the loop back into the manifold.
4. Continue until temp reading gets too high, then shutdown
5. If you have an overflow reservoir it should go down as it replaces air; otherwise the level in the manifold should go down; add 50/50 mix
6. Wait until engine cools. Repeat until temp holds at normal operating temps

Took 4 rounds on my Universal M-18

May have to leave the manifold cap loose during the process.

My heat exchanger was in good shape. I tried to find a radiator shop to clean it anyway since it was off. Little luck finding radiator services and prices were half the cost of a new one!
Josh
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post #8 of 12 Old 10-27-2013
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Re: Engine Overheating

The intention of the thermostat is to bring the engine up to operating temperature and then remain open unless the engine starts to run at a lower temp (NOT LIKELY). I have found that the boat industrially like all manufactory tries to cut corners .At least the auto industries will offer engine sizes according to the load the customer expect to use NOT so with a boat I tried to get a larger motor and was told it comes with a ___ size and that was it. The engine is a extra that reduces the cost of the boat to a more present market value >You can’t even buy a boat without an engine if you want to repower it ,.So those of you with chronic over heat problem look at the engine being under size for the load . You have added enlarged alternater larger prop and loaded the poor boat to an inch of its max waterline and live aboard , then expected it to perform as it just left the show room floor. You may have to REPOWER to get what you want or need,
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post #9 of 12 Old 10-27-2013
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Re: Engine Overheating

Hello,

Have you verified that the engine water pump (not the raw water pump) is operating? Any signs of leaks from the water pump? I would verify normal operation of the water pump before anything else.

Good luck,
Barry

Barry Lenoble
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Mt. Sinai, NY

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post #10 of 12 Old 10-28-2013
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Re: Engine Overheating

Hi,

- find the reason fresh water needs to be added, likely a pin hole in cooler due to not enough attention over the years paid to the cooler zinc
- you can add a cleaner to your coolant side (fresh water). They generally take a few hours running to work, drain and replace coolant
- Make sure your fresh water pump is working
- Check the temperature of your exhaust water, should feel like shaving water
- Get all of the air out of the system

Good luck!
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