Overheating issue

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cmariner32

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1989 Crusader 454 fresh water cooled. Last winter, I replaced the exhaust elbows and had the raw water pump rebuilt by Depco Pumps. All the hoses on the engine were replaced also. Last year the engine would purr along at 180 at cruise. Since the elbow and pump replacement, the temp this summer seemed to run 190-200 at cruise. The exhaust water volume seems good. I backflushed the U oil cooler-found some grass in the intake side and removed-no change. The raw water temps on the heat exchanger show 104 in and 172 out at 2000 RPM at the dock. The manifold temps are 112 in and 177 out. Yesterday, coming back from a day out, the temp skyrocketed to 220 and the high temp alarm came on. I slowed to slow speed and the temp came down within a few minutes and at 2000 PRM and lower, temps are normal. Checking GVP's Cooling System troubleshooting guidelines, the heat exchanger should only be picking up 30-40 degrees-not the 65-degrees that it is. Thinking maybe I had a blockage on the intake side of the HE, I pulled the cap but found only 4-5 tubes that had some crap covering them-not enough to cause the overheating. Sea strainer checked and clean. At this point, I am at a loss as to what could be the problem. Suggestions gratefully welcomed.
 
Possibly debris on the intake of the strainer? Try reverse flush through it and see if that solves your problem I would also try reverse flushing the exchanger. If you had some tubes with visible blockage you may also have tubes with crud inside them.
 
I had a problem like that once, turned out to be the thermostat.
 
What temp does the other engine run at? The 60* thermostat could be off a bit but seems to be working close enough since temps are reasonably controlled at lower rpm. But even the 180* is a bit high. If by some chance you picked up a plastic bag , the high overheat could have been a 1 shot deal.

- As John suggests, I would check the hull intake screens and if possibly above them for fouling. I had "Great South Bay" -type pickup scoops ( by Groco)installed this year because they have hinged hatches in the scoop strainers so I can finally inspect up in there and properly clean out .

-How old are the elbows? Do you have a regular replacement schedule? Can you indefinitely keep your hand on all of them comfortably at cruise speed?
-Check suction hoses on the RW pump and from H/ex to circ pump as the support coil springs corrode and disintegrate on the former and the coil can migrate (contract) toward the circ pump and away from the H/ex exit on the latter. Either situation can allow partial collapse of the suction hose at higher RPM pump demand.
-Look for any cooling system hoses that may be at all bend or hanger -crimped.
-Check tightness of hose clamps and replace any hoses with cracking at the clamps or elsewhwere that might let air in on the suction side. Same with sea strainer seals and cap o-ring.
- Check the tubes in the U-tube cooler if possible, - there may be debris that won't back-flush.
 
Inboard or I/O? What type raw water pump?

Could be intake hose partially collapsing at higher RPM's. Can be caused by blockage and or air leaking somewhere on intake side.

Can still be raw water pump. If debris got up to the H/E, it could have caused problems getting by the pump.

180* isn't a problem at all. Even 210* won't hurt the engine. She actually runs more efficiently at 210*. It's just that the cooling system is designed to run cooler as a safety aspect...and keeping the engine bay cooler. That's another thing. How is your engine bay fresh air system working? Try running with the hatch opened a bit.
 
Is the impeller intact? Even though the pump was recently rebuilt it would be worth having a look. A broken off impeller fin lodged somewhere downstream could cause a blockage.
 
temps that increase and decrease with load are usually raw water related. Nothing to do but start at the inlet and check everything again.
 
Good thoughts. All the hoses were replaced last winter so they should not be the problem. I have a diver cleaning the hull, intake and running gear monthly so that better not be the problem. The raw water pump is the standard Sherwood E-35 pump which I had rebuilt by a reputable pump company in Clearwater. One question that I have is that I think my starboard engine is counter-rotating. If the impellor is installed for the other rotation, would it correct itself? The other engine runs at 180...slightly higher at high cruise-our water temp is/was close to 90 for most of the summer-now 83. I had IR'd the T-stat housing at the dock and was showing 165 with the other temps as indicated in my first post. Elbows and swivels were replaced last winter. I hesitate to break open a freshly rebuilt raw water pump to check the impellor. Bruce, my feeling is that it is a raw water issue. I just hate going back through components that were just replaced at the beginning of the season. I have only a few more weeks of regular Sunday outings. I was hoping to get into the cooler months before having to start on my winter projects which are quickly piling up.
 
Just because you have a diver come once a month does not preclude you from sucking something up to the intake grill. Taking the cover off the fresh water pump to check the impeller is not big of a deal. Three screws/bolts and it is off. At least then you know if the impeller is good or not. Back flushing your system and checking the impeller really are not much of a project. More like maintenance. As others have said, it may have just been a plastic bag or the like that was sucked up just long enough to spike the temp. I would do those two things and go out for another run and see if it repeats at cruise.
 
quote:
Originally posted by cmariner32

I replaced the exhaust elbows and had the raw water pump rebuilt by Depco Pumps. All the hoses on the engine were replaced also. Last year the engine would purr along at 180 at cruise. Since the elbow and pump replacement, the temp this summer seemed to run 190-200 at cruise...............
Click to expand...


Troubleshooting 101 - If something was working fine and you did some work on it and now it isn't working fine, check your work. Something you did caused the problem.

Go back and check your work. Wrong parts, defective parts, installed incorrectly, etc. Also check things you did while changing the parts. If the pump is belt driven, is the belt tensioned correctly?
 
If all the hoses were replaced recently the clamps may not be tight now if they were not all checked/retightened well afterward as the hoses compress and bands stretch slightly.

But if there was a suction air leak I'd think there might be more of a low RPM temp issue. Your issue sounds to me more like a higher rpm flow supply not meeting demand.

But see if you can isolate the primary problem side of the cooling system as suggested by checking with your hand on all the elbow tops at higher rpm when warm. If it is hot look at the RW side, if cool (or comfortably warm) -FW side.
 
Ron...I thought I had it diagnosed when I found the raw water pumpt somewhat loose and tightened it to spec-but didn't solve the problem. John....I will pull the cover off the raw water pump if this weekend's investigation does not find any other culprit. Sandy...while the elbows have been on the hotter side of comfortable at high cruise speed...does not seem to excessive although I will recheck the temps again under load. I really appreciate the input jfrom everyone as this is really driving me nuts (it's a short trip). I have to figure its something really simple that I am just overlooking.
 
That simple overlook might be the raw water impeller. When the new one's were installed did you lube them? I suggest checking them a damaged one will generally cool at lower RPM's but under engine loading it will quickly show signs of running hot.
Cooling isn't something I would dismiss or put off.
Bill
 
Ron brings up a good point. First, was there any overheating prior to the work being done?

Just because work was done doesn't mean the work was done correctly.

Really sounds like the raw water pump is bad
 
When I replaced my Merc elbows this spring, I had to choose the proper gasket to match the old one. Could This one also have different gaskets available with the wrong one selected? Of course you have to remove one of them and replace the gasket to find out.
 
I tried everything I could think of to fix an overheating problem only at high RPMs. The solution - belts weren't tight enough.
 
What Ron just said. I was looking back at your OP and you said you had been out for the day (i presume you at some point where running on plane) and when you opened it up to come back is when you got the overheat. If you had just replaced the circulation pump it is entirely possible that it simply slipped a mm or two. One of the nice aspects about serpentine belts and a belt tensioner is you don't have to worry about that.
 
It has been running hotter than normal all summer since I replaced the elbows and raw water pump. Until last weekend, it never ran over 200 degrees. I guess I should pull the raw water pump and inspect, but the water flow at idle and even 2000 RPM coming out of the exhaust port seems normal which is why I originally did not suspect a water flow problem. John, I had just tightened up the loose raw water V belt thinking that might have been the problem for the 200 degree temps but then it actually overheated. I have fresh water cooled engines and the gasket choice is irrelevant as I have a SS plate between the manifold and the elbow so no water goes from the manifold to the elbow. Thanks to all for suggestions......hopin one will "click" and help me solve this frustrating problem....stay tuned.
 
quote:
Originally posted by cmariner32

........... I had just tightened up the loose raw water V belt thinking that might have been the problem for the 200 degree temps but then it actually overheated. .....
Click to expand...

Explain how that could happen.

I was talking about the belt (on my engine) that turns the alternator and the engine water pump, the one that moves the coolant throughout the engine.
 
Ron, the freshwater belt tension is fine-or at least I thought it was-I will check it closer and maybe tighten it up some more based on your experience. The raw water pump belt was the belt that had loosened up somewhat from when I replaced the belt and raw water pump last winter. In my mind, 200 degree is running hot, but not overheating.
 
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