3.0l Merc, Alpha One drive, Engine revs back and forth on its own?

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Pescado48

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Jun 4, 2013
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22
Hello All,

My boat has been running good for the last couple of weeks, however last time on the water i noticed when going to high speeds the motor revs back and forth on its own. Unfortunately the tach on my boat is not working right now so i dont know the rpm values. Also the engine is not turning off completely (dieseling) never did this before, Any thoughts ? Thx.
 
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alorio1

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Jul 1, 2013
Messages
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Re: 3.0l Merc, Alpha One drive, Engine revs back and forth on its own?

If nothing is moving mechanicly with carb linkag, your fuel filters are clogged. There is one on the carb inlet(brass) and usually one before the fuel enters into the fuel pump and the fuel pump itself probably has one also.
 
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Pescado48

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Jun 4, 2013
Messages
22
Re: 3.0l Merc, Alpha One drive, Engine revs back and forth on its own?

Can engine alignment have anything to do with this? i ran the boat on my drive way, at higher rpm's sounded noisy!
 
Bondo

Bondo

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Re: 3.0l Merc, Alpha One drive, Engine revs back and forth on its own?

Pescado48 said:
Can engine alignment have anything to do with this? i ran the boat on my drive way, at higher rpm's sounded noisy!
Click to expand...

Ayuh,... Welcome Aboard,.... Alignment should be Checked, but no, it wouldn't cause yer issue,...

Check the distributor shaft for Play,...
 
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alorio1

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Jul 1, 2013
Messages
34
Re: 3.0l Merc, Alpha One drive, Engine revs back and forth on its own?

You can't run engine with outdrive in the up position or trailer position, even in neautral. If you have noise with outdrive close to normal trim position you may have other problems. Your gimbal brg may need to be greased, have you greased your gimbal brg lately? I found the gimbal brg takes grease well with the outdrive lowered and engine running and of course muffs and water on. It does not have to be in forward or reverse while greasing.......
 
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alorio1

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Jul 1, 2013
Messages
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Re: 3.0l Merc, Alpha One drive, Engine revs back and forth on its own?

Mine will diesel also if I use 87 Oct. I have to run the high Octane fuel in my 3.0 GM engine.
Pescado48 said:
Hello All,

My boat has been running good for the last couple of weeks, however last time on the water i noticed when going to high speeds the motor revs back and forth on its own. Unfortunately the tach on my boat is not working right now so i dont know the rpm values. Also the engine is not turning off completely (dieseling) never did this before, Any thoughts ? Thx.
Click to expand...
 
P

Pescado48

Cadet
Joined
Jun 4, 2013
Messages
22
Re: 3.0l Merc, Alpha One drive, Engine revs back and forth on its own?

Thanks guy's good info.
 
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