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Engine noise Mercury 75 hp 1990

G

Gustu

New member
Hi,
I have recently bought a 1990 Mercury 75 hp. Today I went for a test drive and when the motor was running on slow idle there was this engine noise. It sounded just like the gear was near to go on. When the motor was running on speed I didn´t hear the noise but when I came back to the harbor and the motor was running on slow speed the noise was there again. Otherwise the motor was running perfectly and I really enjoyed the sound of the motor in high speed, it was like music in my ears. I really hope that the engine noise doesn´t mean anything really bad. My new boat is an Elan 495 GT family, and I like it very much.

Thanks
Gustu
 
If you have a single shifter,the gear can be slipping a little,and when you push it full throttle it puts the gear all the way in and thats might be why you dont hear it full throttle.I had one do that to me a long time ago.SO check your cable adjustments.
 
There is one thing I didn´t remember to mention and it´s that you can hear the noise even when the gear is on and I´m driving on slow speed. Is it still possible that the noise comes from the gear?
 
Is the oil injection system working properly ( bypassed by any chance )-------------------Have you installed a new waterpump impeller ???-------------------------Put a big screwdriver ( or broom handle ) to the block and then to your ear to see if you can pinpoint where the noise is coming from !-------------Control will fully shift the motor into forward before it applies throttle , so I doubt that it is gear noise.
 
The oil injection system is not bypassed. I´m going boating tomorrow so I have to continue the examination of the problem. Than you for the advices. Have to try them.

Thanks
 
Hi,
I was boating today and I realized it is´nt possible to check the motor very much when you are speeding on the ocean. I have to do the checkout with the motor runnig in the yard. Someday later. Today I checked the oil injection system, and it seems to work perfectly. I also think the noise is something that almost belong to old machines. When I drive in high speed the motor is runnig so smootly, it´s almost like music for the ears.
 
Likely it will run ok.--------------Just run it and if it gets worse than it will be easy to pinpoint the problem !!
 
Hows it going racerone I have a question! I have Three carbs and the bottom one inside the fuel bowl keeps getting alot of black stuff tat looks like soot in it,like you would see on a piston.Never seen this before,and would like to have your opinion if you dont mind.
 
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