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Old 02-20-2005, 05:42 PM
vertical202 vertical202 is offline
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Overheating

I have a 27 Ericson with an Atomic 4 which has had $2700 in upgrade and a rebuild 3 years ago. I has had fresh water cooling and a adjustable thermostat installed on it. Since I bought it, it has had a overheating problem. It runs perfectly at idle to 2000 rpm with no load on it. When underway, at anything above about 1000 r.p.m, it quickly overheats. The adj. thermostat can be adjusted from 110 to 140 degrees, but I have noticed that even when at idle in neutral at the dock ,it idles at about 150 degrees. I bought a higher gpm shoe from Moyer for the raw water pump and raw awter discharge seems to be more than adequate. I have also checked the fresh water pump, and it seems to also be working properly. Both impellers are new. When under load,underway at anything above0 about 1500 rpm or 3 kts., it quickly begins to overheat with the temp. climbing to 200 degrees and above. That is when I idle it back down and turn it off to let it cool, and go through the process again just to get back to the dock. When it overheats, I notice a reduction of raw water output and the beginnings of exhaust steam. Today I am going to remove the adj. thermostat, and plumb the heat exchanger directly, to eliminate the adj. thermostat as a possible source of fresh water circulation problems. I know of no way to determine if the problem is fresh water or raw water circulation problems. Both pumps seem to be operating properly. In 01 when all the upgrades were done, the block and head were rodded and boiled out as part of the rebuild process. The rebuilder said that although there was scale and buildup,the water jacket looked typical and circulation in the block would be no problem. I have tried everything I know of to troubleshoot the problem with the exception of possibly the head gasket, but the motor runs so well with no plug fouling or evidence of water in the oil, or combustion products in the antifreeze. The guy I got the boat from is a friend of mine and bought all the parts from Moyer but had the machining done locally. I had an experience in the past with a VW rabbit, when after draining the cooling system and refilling with antifreeze, it overheated. The problem turned out to be an air bubble in the water jacket. When I finally discovered it and was able to bleed the remaining air out of it, the heating problem immediately resolved itself. I am not familiar with the Atomic 4's but maybe there is a similar fix or possible problem. Any help would be greatly appreciated by anybody willing to respond. Thanks !! Gerry
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Old 02-21-2005, 06:39 PM
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Gerry,

Since the raw water coming out the back of the boat reduces (to the point of generating steam), your problem is undoubtedly caused by a restriction developing within the raw water loop. Your internal fresh water (antifreeze)
loop has nothing to do with the amount of raw water leaving through the exhaust system.

The perplexing issue is that the flow coming out of the exhaust is apparently normal in the beginning. This means that we have to look for a restriction the develops (or at least worsens) as the engine heats up. I suppose the Indigo Electronics controllable thermostat could be the culprit, but I don't consider that to be very likely, unless it has been plumbed incorrectly from the beginning of the problem.

In case the problem persists after removing that thermostat, the only history I can think of in this connection is the rubber lining of the inside of the exhaust hose breaking away from the rest of the hose and crumbling up inside the hose, blocking the flow of water. If this is your problem, you can usually hear a difference in the sound of the exhaust just before the temperature begins to rise.

Best regards,

Don Moyer
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Old 02-22-2005, 11:41 AM
dtinder dtinder is offline
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Cool exhaust hose

Just an add on to Don's idea about a crumbling hose restricting flow:

I chased an "unsolvable" over heating problem for weeks---(302 Ford)

Multiple therostats---bypasses----cooling hoses---elbows---manifolds---you name it I tried it---the former owner sold me the boat because he could not find the fix.
As it turned out the exhaust hose (4" Name Brand hose) was, during its life time, subjected to a serious overheat---of unknown cause. The inner liner of this wire reinforced hose seperated from the other laminates--causing, in essence, a "blister" (approx3"X12") inside the hose. As things heated up, so to speak, the blister, responding to some vague law of physics, expanded accordingly---and progressively---

This led to the little known and accepted "Dave's Law" of thermodynamics: Subjective analysis of exhaust water flow is usually WRONG.

Best to everyone,
Dave---in sunny Ft Myers----80F ESE@10-12
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TimBSmith (07-18-2022)
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Old 02-22-2005, 12:42 PM
vertical202 vertical202 is offline
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Cool Overheating with a cool head..Ha Ha!

Thanks to both of you, Don and Dave. I am heading down to the boat today to by golly, find the problem! Thanks for your thoughts about the exhaust hose lining possibility. My friend that I bought the boat from was no sailor, but mechanically anal. Pretty much everything engine related including the exhaust hose is nearly new, but something I am going to check anyway. When I first discovered the overheating problem, my first suspicion was incorrect routing of the hoses of the two engine water systems. I thoroughly checked these first against the installation instructions, and all routing is correct. I will be buried in the bilges all day today determined, to solve this thing! I'll post again whether I find the solution or not today. Thanks again! Gerry
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Old 02-24-2005, 12:13 AM
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Smile Cooler head prevailing

Hi Don, Just thought I would get back to you to let you know I found the overheating problem. I had checked the raw water strainer first thing when the problem developed. It was clean. Today I removed the Indigo heat exchanger just to check and flush it, out of the boat. When I removed the top and bottom plates, I found one of the problems. Seaweed in the top strainer. Bottom strainer had a little in it too. The instructions for the unit didn't mention that the heat exchanger had 2 strainers in it. The top one wasn't entirely blocked, but apparently enough to create a significant obstruction when at higher rpm's under load. I also discovered that the adjustable thermostat was screwed out too far. The knob only turns about 1 full turn from side to side for full adjustment range. The knob is prevented from going more than one turn by a stop on the knob and a lug on the thermostat body. After I cleaned the strainers, at about 2000 rpm in gear, the engine still got up to about 210 degrees. I knew that everything in the cooling system was operating properly, so I took the knob off the thermostat and turned the thermostat shaft clockwise until almost seated. That would allow the greatest amount of cooling. I replaced the knob and started it back up and again ran it at 2000 rpm under load. This time the temp went to a max of 190 degrees. At Idle with no load it cools down to about 150 degrees. These temps seem to me, to be about right. To make a short story long, I just thought I would let you and anybody else know what I found out to be the solution to my problem. If you have any thoughts on what I've done, or the temperatures my engine is now running at, please let me know. I am happy for now, and going to go on a shakedown this weekend. Wish me luck!! Thanks Gerry
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Old 02-24-2005, 11:21 AM
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Gerry,

Great job!

You're certainly OK at 190 degrees for now, but we wouldn't want to see temperatures creep into the 200 range. I'd keep an eye on things as we get into spring and summer. Unless you're in unusually warm water for this time of year, my instinct is that there is still a small glitch somewhere in your system.

Best regards,

Don
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