Losing RPM

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Robby662

Cadet
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Apr 9, 2007
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17
I have completely repaired my Mercruiser 3.0 140 engine and drive unit. Everything is ok except for one thing. When I take a curve or turn at WOT I lose RPM, even after I straighten back up and get going good it loses from about 4800 down to about 4100 and stays that way until I throttle back down and start over, then it goes back up to 4800. Have no clue if this is serious but it does not seem right. Any ideas?
 
Bondo

Bondo

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Re: Losing RPM

Is there Any Play in the Throttle Cable,..??....

How Old a boat are we talking about,..??....
 
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Robby662

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Apr 9, 2007
Messages
17
Re: Losing RPM

1985 - I seen the receipt were all the cables were replaced 2 years ago. It goes into gear smooth and other than just losing the RPM in turns, I can not tell there is anything wrong. It does not hesitate in straight aways as far as the throttle goes.
 
Reel Poor

Reel Poor

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Re: Losing RPM

Is the boat actually slowing down or is it just the tach that appears to be reading wrong ?
 
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Robby662

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Joined
Apr 9, 2007
Messages
17
Re: Losing RPM

You can tell it is slowing down. My speedometer does not work but the sound pitch of the engine is different also. I guess it would have to be a cable. I made sure when I took the manifold off to leave the linkage and stuff exactly the same when I put it back on. I hate to even mess with it seeing how it is so close. It just bogs down in a curve and will not completely recover.:confused:
 
WillyBWright

WillyBWright

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Dec 29, 2003
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Re: Losing RPM

It should recover as soon as you straighten out. If it doesn't, I'd suspect a gummy carb. Put some Berryman's B-12 in the tank, following their instructions (WalMart). Don't over-do it. If it doesn't correct in a tank or two, do a carb rebuild.

Also check to make sure all the screws that hold the top of the carb to the bottom are snug.
 
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Robby662

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Apr 9, 2007
Messages
17
Re: Losing RPM

Is it better than seafoam? (berrymans) I got all the old gas out and added the seafoam per instructions with new gas. I notice it started smoking a little after the seafoam. I would have never guessed the carb. I am sure it is due. If berrymans is better, will it hurt to add that AND seafoam, seeing how the seafoam is already in there.
 
Reel Poor

Reel Poor

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Re: Losing RPM

I'm not for the mechanic in a can, although they do have their places. I would not add another mechanic on the same job. Let the first one see if he can fix it. :D
 
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