Engine Overheating on Helms 30 - SailNet Community

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  #1  
Old 07-27-2006
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Engine Overheating on Helms 30

I have a Helms 30 1976 model number 15. It was upgraded at some time to a Volvo Penta diesel ingine. The engine temperature is around 200 on a new gauge. The fresh water system mixes with the exhaust in the heat exchanger. The exit port is exhaust and water 1 1/2 inches in diameter. This port is just below the stern and about 12 inches above the water line. The water coming out is only a spray. Never a steady stream. The intake hose is 3/4 inch inside diameter. It seems to me that more water should be exiting the system. I am told this diesel should run between 160 and 180 degrees.
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Old 07-27-2006
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Ummm... The freshwater system probably doesn't mix with exhaust in the heat exchanger. Most diesel engines have a heat exchanger, and the freshwater system runs through a heat exchanger which allows it to dump heat into raw seawater, and thereby cool the engine... but the freshwater system is generally a closed loop system.

If the raw seawater is mixing with exhaust, it may be only coming out as a spray, as the seawater may be partially vaporized...but this sounds like you've got a problem. Most thermostats are supposed to open at 180 degrees or so. Have you tried flushing the freshwater system out, and seeing if any of the internal freshwater cooling passages are clogged or blocked? Have you flushed the heat exchanger and raw water system and tested for good flow through it? Have you checked the impellers on both the freshwater and seawater sides of the system?

I don't know enough about your Volvo Penta Diesel engine to say more...
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Old 07-27-2006
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I replaced the raw water pump last summer. This was done by the boat service at my marina. The freshwater pump is belt driven on the front of the engine. It isn't leaking or making any unusual noise. I have temporarily removed the thermostate in case it is sticking. I am more concerned about the raw water exit with the exhaust. The stream is less than the bartender at the Ramada Inn bar pouring a burbon at happy hour. A Benetau 29 with a similar engine on the pier shoots a 1/2 inch stream 3 feet out of the side.
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Graphic description, but effective... I would still check the raw water impeller...as it doesn't seem to be pumping much raw water...and that is probably why the temp is climbing. Not enough raw water...not enough heat transfer...not enough cooling.
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Old 07-27-2006
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Smile Suggestions

From the description I would guess the problem is the raw water side of the system. I would guess that the fresh water system is OK with the removal of the thermostat and the fresh water pump not leaking or making noise. You cannot be sure but for now I would concentrate on the raw water side.

Raw water pump or impeller – probably not the problem with the installation of the new pump

The total list of things that I would check and in the order I would check them are

Clogged raw water strainer or intake - Strainer easy to check. Checking the intake is probably best done by diving the boat. More risky would be to take the hose off the through hull and open the valve to see what kind of flow you get. I am sure you are aware of the potential to sink the boat doing this.

Clogged heat exchanger – you will have to remove it to have it checked but many times fouling can restrict flow and heat transfer and make the engine overheat.

There is what I call and exhaust snubber down stream of where the raw water and the exhaust gases mix. This could be clogged. I have only seen pictures of this device and have never taken one apart but it has been mentioned as a point where carbon can cake and restrict exhaust and water flow.
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I'm not familiar with your engine, but typically the point at which the raw water enters the exhaust in the exhaust riser scales up. I have to clean (scrap) mine every year and ever other year replace the exhaust risers or the flow will be reduced. If your raw water pump and strainer are ok, look at the risers next. You said new engine. New to you? How many hours?

Wayne
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Old 07-28-2006
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Wayne25

I would be interested in how many hours of operation you have between cleanings of you riser. Could you give us and estimate.

Thanks
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Old 07-28-2006
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suggestion

Don't know if the spitting is normal for your engine or not..would guess you would like to see a nice flow...couple things...shut off the valve and check the inlet/suction hose to make sure there is no leak... could be air leak...possibly replace it. the next is to actually put a heat gun on the the engine to determine if the gauge is accurate. It is possible to have a poor ground on the gauge thus giving a poor reading on the guage. While I'm not a diesel specialist, what your doing is just testing... it is not advisable to run too long without a thermostat.
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Old 07-28-2006
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Rendezvous...I think MikeGC has it right. A couple of things I would add...
1. First check the water input through hull. anything can get in there and restrict your available incoming water.
2. Next...check your strainer to make sure it is clear.
3. Then take the hose off the input side of your impeller pump and make sure you have good flow to the pump.
4. Then take the output side hose off and turn the engine on for a minute to insure that your pump is operating full force. Despite the pump change last year it is entirely possible that your impeller is only partialy working or has lost a blade. If you don't have god flow...replace the impeller with a new one (suggest Globe long life impellers). If the old impeller has broken fins...you'll have to go digging through your piping/heat exchanger to retrieve the missing bits as it is likely that these are blocking your flow.

Next steps are checking the injector elbow for clogs or collapsed old hose and finally...pulling the heat exchanger out and giving the inside tubes a reaming or acid bath. If it comes down to the heat exchanger...another method is to feed a weak muriatic acid solution through the raw water intake hose with the motor on...let sit for a couple of minutes after you see it bubbling out of your exhaust...then reconect the water supply and turn engine back on and use the seawater to flush out the remainder.
Hope this helps!
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Old 07-28-2006
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Jackson, MS??

Probably just a Water Moccasin that swam into your thru hull and is clogging the intake hose.

Put your face real close to the hose coming out of the thru hull as you take it off!!

In all seriousness, Camaraderie has the step by step diagnosis. Anything from debris in your thru hull, to a semi-clogged strainer, to a bad impeller, to worst case scenario of a heat exchanger that needs to be replaced all could cause this.

While you are checking the raw water circulation system, don't forget to check that your coolant is topped off (50-50 mix) in the closed system that makes up the other half of the cooling system. Also check the oil dipstick to make sure you do not have coolant mixed in the oil.

My guess is that you have a bad impeller in the raw water system, but you have a spare impeller kit onboard, right? (hint)
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