over heat

[bud37]

Years ago I had the same problem after an impeller change.......pump would not pump....turned out the suction hose at the pump connection had a very, very small crack, did not even leak water.....cut 1/2" off and all was well. I will say after spinning the pump dry trying to get it to prime I put a new impeller in to be safe after finding the split.

So I guess I am saying have a real good look, even the smallest thing will stop those pumps......you changed the other side and all was well.

[pepmyster]

Thank you. This week end I'm going to remove the out hose from the housing, then check the out put to make sure. If not, going to go backwards down the line.

[pepmyster]

Okay, this is the situation. I went to the very, very beginning. Removed the anode from the heat exchanger, looked inside, bone dry and clear. I went to the plug of the service port, to run it one a garden hose, when I started to remove it, you could hear a suction whistle. I retightened it with a wrench, it’s plastic you know, tight enough to make sure of a good seal. Remove the strainer basket top, verify the gasket. Looks good. Put some dielectric grease on it and placed it on with kid gloves, tightened. Okay. Loosen the clamp on the output hose to prepare to remove it to see when the engine is running if any water is coming out. While running, slight water. While running, hold the output hose to catch the water that is coming out of the impeller. Install hose. Keep running for 2 minutes. Stop the engine. Took a breather. Start motor again, remove the output hose again, tons of water coming out now. aim again the hose to the output and reconnect. Tighten the hose. Ran engine for 10 to 15 minutes, manifolds cold to the touch. So, there was obvious air pocket in the system caused because of siphoning air. It was either the service port or strainer. Basically I went back to all that was touched by me while doing the impellers. End of saga. Hopes this helps anyone with this idiotic problem. Have a great weekend.!

[Phrancus]

Well done, good that it is solved and you can be on your way.

Cheers!

[bud37]

Thanks for posting....sometimes it is the easy stuff heh......So a question for you.....what did you use to lube the new impellers ?

[pepmyster]

I used dielectric lube. The same synthetic lube we use on rubber, slider caliper pins, electric circuits.

[Midnightsun]

Really glad you got this figured out. The good part is it was free except for your time and sleepless nights worrying about it.

[pepmyster]

SSDD. Okay, here we go again. Went for our real first good cruise on Sunday, after the winds finally gave us a break. After about an hour in , the Port engine started to over heat. Go to our destination on 1 engine. Stopped and relaxed for about 1/2 an hour. During that time I checked the regular stuff, strainer and such. All very good. Strainer full. Started the engine, ran fine. On with the show and started to head back to anchor somewhere. Lowered my rpm's to idle speed to start to set the anchor, there the Starboard engine started to over heat. Gezzzzzzzz I'm fed-up. Headed back to the marina on 1 engine again. Before getting into my slip, I started the other engine to maneuver the boat. Back to square 1. The only thing I can think of is the dielectric grease I put on the impellers is causing it not to cause the suction by being too slippery. I'll check again this week-end.

[Phrancus]

Auch.... that's annoying and a weekend-spoiler.

I can only share my experience with our own engines, hopefully there is something that makes sense to you in your situation:

In the beginning the port engine overheated at strange times. Not always at the same time I mean. Sometimes at idle, sometimes on higher RPM. Very annoying for problem/cause investigations.
Took the heat exchangers apart, some calcium but nothing unexpected (except that some idiot use a saw to open it and botched it back together making it difficult for me to close it all up). checked all the hoses and pipes (older Volvo Penta with crap connection type, adding to the agony). FFWD the times we went out and shut it down before or at the overheating beep. In the very end it turned out that vanes of an impeller had dropped into the suction hose and those were sucked up to the pump and blocked the suction side. Not always, as they sunk back down the suction pipe/hose.
Found out about it when I winterised by taking the suction hose off from the pump to bleed the raw water before having it suck in the antifreeze. Suddenly there were impeller vanes in the bilge....
Much later I removed the drives and found a lot of clamshells in the intake. That in itself was not the cause (both sides had that, only one had the overheating)

At the moment, the other engine starts to whine intermittently at idle: oil pressure at the edge, sensor/wear/oil... to be investigated.


Do you measure the engine temperature with some infrared-gun as well? Just to make sure that the temperature sensor is working correctly?

[pepmyster]

The impellers are brand new. Oh yea, the sensors are correct, You can feel the manifold heat. Closed loop system.