Water cooling switch???

[AppyDaze]

Hello all,

I have just purchase a 1986 hunter 34.5. During engine testing process I noticed that there was no water coming from the exhaust. I asked the previous owner about it and he said that the boat has never over heated on him and that he thought water was coming out and never noticed it. In doing research on the engine (3GM30F) I came across a section in the manual called the cooling water switch. I wanted to ask everyone if this cooling water switch engages the engine to only draw sea water into the engine after the engine rises past a certain temperature, or does the engine constantly draw sea water during operation?

I am going to investigate the impeller and raw water strainer tomorrow to insure there is no stoppages but I just wanted to see if I should wait and let the engine reach a certain temperature before worrying about water coming out of the exhaust.

Thanks,

Jacob
Appy Daze

 

[splax]

Jacob,
You should have a gurgling, "burping" exhaust sound, that is your water muffler. I think the raw water pump puts water there, especially when the engine is not up to temperature and the heat exchanger is not accepting raw cooling water. I did not read about the water cooling switch, I will look it up when I go to the boat this week.
I definitely recommend changing the raw water pump impeller, because you don't know what has happened previously. If it looks in good shape, keep it for a spare.

 

[AppyDaze]

Thanks for the reply. This is what I found.

http://www.yanmarmarine.co.uk/pdfs/service_manual/EPB5494.pdf

Go to page 218.

 

[Johnb]

More knowledgeable people than me are going to chime in, but in the interim

1 That switch on page 81 is for a high temperature alarm
2 If there is no "sea water" coming out of the exhaust that is a problem, including all the knock on effects of overheated exhaust system in addition to an overheated engine.

 

[Claude L.-Auger]

Jacob,
Judging by the terms used, you seem to have a British manual ! The "switch" you are looking on is indeed your high temperature alarm. You do not turn it on or off as it is wired to your ignition switch and will activate the red light in your panel as well as the buzzer if the engine overheats. You should be getting water gurgling out of the exhaust at all times when engine is running. Check that eveything if free from blockage, from the water intake valve to the "skimmer" to the impeller. A simple test to make sure you got good flow coming in is to disconnect the outlet hose from the impeller, and after having decompressed the engine, hit the starter button for a few seconds. If you don't have a solid flow of water, then something is blocking water from coming in or the impeller is defective.

 

[gfrazzle]

You DO have the engine cooling seawater through-hull open don't you?

 

[AppyDaze]

Yes the through hull is open.