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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15879
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have a 2005 150 Mercury Optimax. Saturday I was fishing on

Customer Question

I have a 2005 150 Mercury Optimax. Saturday I was fishing on Toledo Bend and as I was backing up from my camp I noticed a small whistling noise that I had not heard before. I had good water pressure so i took off and went across the lake running about 4500 RPMs. When I stopped the engine was making a funny noise. When i turned it off and tried to recrank it all it would was turn over. It would not restart. No alarms went off at all.
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.

Hi Billy, my name is Jason

I read what you wrote. These are pretty complicated engines. You didn't ask any specific questions so I don't know what kind of information you are looking for. How is it I can help you?

Customer: replied 1 year ago.
If the powerhead went out would the motor lock up or would it still turn over? I have never had any problems out of this motor. I just cannot understand why the motor ran so good across the lake then shut it down making a slight knocking noise. I turned it off and tried to recrank it and all it would was turn over.
Expert:  Jason replied 1 year ago.

It all depends on exactly "how" the powerhead went out. If you blew say 1 piston the engine would still run on the other 5 cylinders. If it threw a rod, the engine would lock up.

As for the whistling noise. It is normal for the air compressor to make a whistling noise. What you are actually hearing is the compressor sucking air in through a little nozzle, and that is what makes the noise. If I had to guess, and I'm only saying this because you made mention of the whistling noise, is it is possible the air compressor went out. And when the compressors go out the engines will pretty much not run. I don't know how much you do or do not know about the optimax system. Does that make sense to you, or do you need me to explain how the actual EFI system works on the opti?

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