covert cause of engine overheating

[LARRY VALENTINE]

I had just returned from my yearly financial drainage where my 53 footer was bottom painted,
zincs added, and a cracked raw water motor strainer housing was replaced at the local boat yard when after 15
minutes on arrival at my dock the port engine overheated. My friendly mechanic found and
replaced the destroyed impeller. It still overheated.The heat exchanger was found to be full of calcium and
then replaced. It still overheated.
The next adventure involved disconnecting the raw water hose at the exhaust connection [shower head].
Wide open garden hose into the showerhead caused some backsplash suggesting a blocked showerhead and
suggesting a $9k repair bill. Copper/nickel exhaust showerhead.
I found that the engine overheated after 15 minutes in forward gear at the dock consistantly after
injecting various chemicals into the showerhead. I then placed a 2 in. hose from the raw water
exit of the heat exchanger to the dock. Once again the engine overheated after the usual 15 minutes with
almost no flow at 600 RPM but some flow at 1200 RPM. This suggested the problem was not in
the exhaust but perhaps the thruhull, the waterpump, the impeller , the heat exchanger or some of the pipes
interconnecting. I then tightened all hose fittings leading to the impeller, placed the 2 in. hose
prior to the heat exchanger and started the engine. At 600RPM it filled a 5 gal bucket in 10 seconds!
After putting everything back together......no overheating! Lesson: after any work on engine tighten all hose
clamps. I could have saved myself about $1K and many hours of anguish.

The raw water impeller was sucking some air through the system where the hose connected to the pump.
It is not fun being mentally challenged!

 

[racclarkson@gmail.com]

Good post.

If your HE was deposit clogged, you can bet your intercooler is as well (you didn't state engine type). Time to run Barnacle Buster or equivalent through the system and clean all of it out. From what you posted, you haven't (a) run the motor up to load, and (b) haven't run it in summer with higher ambient water temps. Running it up to cruise and max power would be the only test to assure you've got it whipped, IMHO.

Robert

 

[SEVEN]

Thanks for the heads up, I'm not going to wait for mine to over heat. I'm going tighten mine this weekend. Those motors to vibrate. Again thanks.

 

[piripucha]

The pipe that conects the raw water pump with the hose that goes to the sea strainer has a trumpet like or conic shape that lets it to be prone to sucking air so it does not let the pump to prime. I usually make a tape gasket on the slim size and use 2 hose clamps. I once destroyed 2 impellers because the pump did not prime.

 

[LARRY VALENTINE]

Good post.

If your HE was deposit clogged, you can bet your intercooler is as well (you didn't state engine type). Time to run Barnacle Buster or equivalent through the system and clean all of it out. From what you posted, you haven't (a) run the motor up to load, and (b) haven't run it in summer with higher ambient water temps. Running it up to cruise and max power would be the only test to assure you've got it whipped, IMHO.

Robert

I agree. That will await springtime. The engine is a 6V92TA and both sides of the exhaust go into the copper/nickel showerhead. The temps on both engines were compared with readings of the input and output RW on each side of the heat exchanger and engine block in and out of forward gear at 600 RPM. They are now the same.