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Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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My engine is a Perkins 4.236. I bought the boat 2.5 years

Customer Question

My engine is a Perkins 4.236. I bought the boat 2.5 years ago. The exhaust warning light and alarm goes off after about 15 minutes running the engine at load at 1200 rpm at the dock. Sea strainer is clean and water pump impeller work fine. The heat exchange tank was very low so I filled it with nearly 1/2 gallon of anitfreeze. I found antifreeze in the bilge. What is the problem?
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello Richard. My name is Tan.

Coolant in the bilge is a leak from the closed cooling system of the engine. You will have to pressure test the cooling system to find the leak. You can use a radiator pressure tester to perform this test. Put the pressure tester on where the cap goes on the coolant tank. Pressurize to 13 psi. Then with a light look for a coolant leak.

The leak can be from any of the hoses at the thermostat housing water pump on the front of the engine or possible freeze plug. The only way to find the leak is to pressurize the cooling system. It can be done by running the engine but everything is very hot and can be hard to see with a hot engine.

What kind of shape was the water pump impeller? Was the sea strainer dirty? If the engine got hot enough the coolant could have boiled out of the over flow.

Customer: replied 1 year ago.
I did the pressure check and tested for 15 minutes. Pressure held fine at 5 lbs.
Customer: replied 1 year ago.
Could not find any hose leaking,
Customer: replied 1 year ago.
impeller was like new, sea strainer and chest clean
Expert:  Tan replied 1 year ago.

If you didn't find a leak then the only way coolant will get in the bilge is from over heat and the coolant boiling out.

Does the engine over heat now since you filled the cooling system back up?

Expert:  Tan replied 1 year ago.

Do this with the pressure gauge still connected and 7 psi of pressure run engine. Does pressure drop?

Customer: replied 1 year ago.
The engine does not overheat. The exhaust temperature warning light and alarm sound. The engine warning light and alarm do not go off.
Expert:  Tan replied 1 year ago.

Ok on the exhaust pipe where the heat exchanger dumps into the pipe. Remove the hose and fitting and inspect for blockage and corrosion build up.

Customer: replied 1 year ago.
Sorry, but not helpful. Thank you.
Expert:  Tan replied 1 year ago.

So your giving up already. Good luck.

I have no idea what you have done and I am not there to do these checks for you I'm not a mind reader or magician. If you don't want help good luck with your issue. This is a process of elimination.

You think I can solve your problem in 5 minutes and how long have you been working on this issue?

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