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Noel Schembri
Noel Schembri, Marine Technician
Category: Boat
Satisfied Customers: 1951
Experience:  Advanced technical diploma
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I have 2 chrysler 318 marine engines in a boat. Both are getting

Resolved Question:

I have 2 chrysler 318 marine engines in a boat. Both are getting fuel from the same tank. Both fuel filters have been replaced. One engine is running as it should.
The other runs as it should until the boat has been under load for 10 to 20 minutes.
I typically start both and don't leave the dock until each has reached operating temp [140] --both are fresh water cooled and utilize a salt water heat exchanger.
When the boat cruises [at 3100 rpm ] the temp comes up to almost 160 as it always has . After it runs at this temp for 10 to 20 minutes the rmp's decrease automatically to 2900 and fluctuate up and down.If I bring the engine to idle , it dies.
If I start the boat the next day, after it is fully cooled, the engine runs as it should until I cruise for awhile.
Both engines are 22 yrs old, both have rochester carbs. They have been well maintained . No water in the oil. Not loosing any coolant. Russ
Submitted: 6 years ago.
Category: Boat
Expert:  Noel Schembri replied 6 years ago.
Hello my name is XXXXX XXXXX will help you with your problem. It seems as if you have a leaking cylinder head gasket. Best thing to do to check this out is to open up the cooling water reservoir while the engine is revvingg around 3000 rmp and check if you have bubbles present in your cooling system. if yes then you ll need to replace the cylinder head gasket.

Hope i was of help to you , of you need anythig else let me know.

Noel Schembri and other Boat Specialists are ready to help you
Customer: replied 6 years ago.

I won't be able to check for bubbles until this Saturday

It seems to me though, that if I have bubbles in my exhaust, I should have coolant in my oil or at the very least , be loosing coolant -- and I'm not

As I was 6 miles offshore when this first occured and the engine ran for almost 2 hours in this condition---and the following day it ran smoothly for a half an hour, then poorly for a half hour---and then did the same thing the next day

Expert:  Noel Schembri replied 6 years ago.
Ok so first check for the bubbles in the cooling. If you do not find bubbles, then it looks like a hi tension wire has lost it's insulation and may be arcing to ground, thus not giving spark to one or more cylinders. Check out the hi tension leads and distributor cap for any cracks. Ideally swap them between engines and see if it makes any difference. The electrical components tend to act awkward when heated.

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