I recently had the experience of having my engine overheat on my hunter 34. We had been motoring into a stiff wind(17-25) and 3-4 ft waves for about 1.5 hours when the engine overheated.The engine was running at 2800 rpms. We anchored and let the engine cool off only to have it overheat again at idle (about 1500 rpms).I checked the oil level, coolent level, raw water impeller and strainer and found no problem. I dove down on the prop and it was not fouled. I eventually bit the bullet and got a tow. We had to run the engine just a couple of minutes to get into the slip. It again overheated in less than 5 minutes. It seemed that it was taking less time to overheat each time we started it. The next day the mechanic checked the thermostat and said it was ok. He said that the raw water strainer had an air leak at the top and he put some sealant under the lid and put it back on. He also found that the impeller that I had just checked a few hours before was in multiple pieces. The next day I was motoring to my home port and had been running at 3200 rpms on flat water with no wind when it again overheated. I let it cool and then went the rest of the way keeping it below 2800 rpms and had no problems. I noticed small puffs of white smoke coming out of the exhaust on a regular basis. I also noted that the amount of water coming out of the exhaust was significantly increased after the mechanic did his stuff. There is some grass fouling on the bottom. Should I worry about the white smoke and the engine overheating at 3200 rpms ? Does it sound like it is fixed? Thanks for the advice.
engine overheating
- Thread starter jim22335
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Doesn't sound right yet
I am assuming you have a yanmar 3GM. Both the fresh water and raw water model have overheating problem as they age. First check the water intake. Weeds often get in the pickup pipe. An engine flush should help clean the engine but is not generally enough. Scaling in the heat exchanger is one source of problems. The core can be pulled out and washed carefully with household calcium removing cleaners (CLR or Lime Away etc). Both the fresh and raw water models tend to get clogged up either in the mising elbow and/or the small connector and hose on top of it. I am not sure why your impeller got damaged, perhaps too much restriction in a clogged engine lead to premature failure? You should be able to run the engine at 3400 for an hour without overheating.
I am assuming you have a yanmar 3GM. Both the fresh water and raw water model have overheating problem as they age. First check the water intake. Weeds often get in the pickup pipe. An engine flush should help clean the engine but is not generally enough. Scaling in the heat exchanger is one source of problems. The core can be pulled out and washed carefully with household calcium removing cleaners (CLR or Lime Away etc). Both the fresh and raw water models tend to get clogged up either in the mising elbow and/or the small connector and hose on top of it. I am not sure why your impeller got damaged, perhaps too much restriction in a clogged engine lead to premature failure? You should be able to run the engine at 3400 for an hour without overheating.
Look for :
A soft, collapsing supply hose between the through hull and the raw water pump. Check every inch. An inside wall may have delaminated, thus pulling closed under the low pressure that higher speed running causes.. Better yet, just replace it. Many times the bad spot is near impossible to see and continues to stymie diagnosis. An impeller that disintegrates in one session usualy does so due to a lack of lubrication. (Water!) This would tend to confirm the hose diagnosis.
A soft, collapsing supply hose between the through hull and the raw water pump. Check every inch. An inside wall may have delaminated, thus pulling closed under the low pressure that higher speed running causes.. Better yet, just replace it. Many times the bad spot is near impossible to see and continues to stymie diagnosis. An impeller that disintegrates in one session usualy does so due to a lack of lubrication. (Water!) This would tend to confirm the hose diagnosis.
Good Coverage on the Problem
...in the prior two posts. I had the same thing happen. I did have a build-up in the intake through hull that I got out with a gun barrel cleaning tool. Also had impeller debris clogging the front of the heat exchanger. However, I found the real culprit to be carbon build-up at the raw water injection to the exhaust manifold. It created LOTS of pressure, enough to blow the hose off my manifold. And, of course, the restriction will cause you to eat impellers. FWIW, I tool off the fitting and purchased a spring which I put in a drill chuck and ran in and out while spraying card cleaner in it. Worked OK to ID the problem, but not (probably not) a substitute for removing and properly cleaning or replacing the elbow. Good luck. Don't you just hate these problems? Rick D.
...in the prior two posts. I had the same thing happen. I did have a build-up in the intake through hull that I got out with a gun barrel cleaning tool. Also had impeller debris clogging the front of the heat exchanger. However, I found the real culprit to be carbon build-up at the raw water injection to the exhaust manifold. It created LOTS of pressure, enough to blow the hose off my manifold. And, of course, the restriction will cause you to eat impellers. FWIW, I tool off the fitting and purchased a spring which I put in a drill chuck and ran in and out while spraying card cleaner in it. Worked OK to ID the problem, but not (probably not) a substitute for removing and properly cleaning or replacing the elbow. Good luck. Don't you just hate these problems? Rick D.
...and of course you have checked the elbow?
Jim: There are all sorts of things that can cause overheating. Most of which have been covered. The o-ring on the raw water strainer is one that I had not heard about, but it makes sense. It is usually indicated by a water leak. Then there is the infamous mixing elbow. This is a replacment item every 3-7 years if you are in salt water. I would suggest that you order an elbow and gasket and just replace it, if you have not already done it. If the old one is in good shape, you can always clean it up and use it for then next time.
Jim: There are all sorts of things that can cause overheating. Most of which have been covered. The o-ring on the raw water strainer is one that I had not heard about, but it makes sense. It is usually indicated by a water leak. Then there is the infamous mixing elbow. This is a replacment item every 3-7 years if you are in salt water. I would suggest that you order an elbow and gasket and just replace it, if you have not already done it. If the old one is in good shape, you can always clean it up and use it for then next time.
Rick - be careful using gun tools aboard
If you head north, it is no joke. I have a friend who went to Canada several years ago with a gun cleaning kit aboard that he had used for cleaning something on his engine. The customs guys saw it and proceeded to take his boat apart and very seriously question him trying to find his gun. He had no gun but they were convinced that the kit indicated a gun aboard. He was detained for most of a day, had to spend a few hours putting his boat back together and has been grilled and searched every time he has gone into Canada since.
If you head north, it is no joke. I have a friend who went to Canada several years ago with a gun cleaning kit aboard that he had used for cleaning something on his engine. The customs guys saw it and proceeded to take his boat apart and very seriously question him trying to find his gun. He had no gun but they were convinced that the kit indicated a gun aboard. He was detained for most of a day, had to spend a few hours putting his boat back together and has been grilled and searched every time he has gone into Canada since.
3200 rpm's Sounds high...
...for a 3GM (I assume it is). I beleive that WOT is 3200 rpm which would make 2800 rpm a comfortable max. Replacing the impeller sounds logical, even though it looked fine the first time you inspected it. Also, cleaning the strainer and intake. Barring a bad mixing elbow and given my high rpm's concern, above, I think you are OK, now. See the attached link for Yanmar manual and advice.
...for a 3GM (I assume it is). I beleive that WOT is 3200 rpm which would make 2800 rpm a comfortable max. Replacing the impeller sounds logical, even though it looked fine the first time you inspected it. Also, cleaning the strainer and intake. Barring a bad mixing elbow and given my high rpm's concern, above, I think you are OK, now. See the attached link for Yanmar manual and advice.
thanks for the help
Thanks for everyones help. I will be going to the boat this weekend and follow your suggestions.
Thanks for everyones help. I will be going to the boat this weekend and follow your suggestions.
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