Where did the RPM's go?

A

ae708

Chief Petty Officer
Joined
Jun 17, 2002
Messages
591
My boat... 1998 Manta Ray 17'9 with 3.0 Mercruiser I/O, 19 pitch prop used to run, with just me in it, about 48mph at 4900 RPM. Last time out it started great, ran fine up to about 42mph and 4400 RPM (appx) No skipping or misfiring, just runs out of top end. Put on new prop.. same thing... any suggestions..help.
 
R

Ribfan

Cadet
Joined
Apr 15, 2003
Messages
28
Re: Where did the RPM's go?

Do you leave your boat on the water, or have since you last took it out..<br /><br />Stupid question i know, but you would be surprised how much crap grows underneath. and causes speed and RPM loss.<br /><br />If not could be alot of things
 
A

ae708

Chief Petty Officer
Joined
Jun 17, 2002
Messages
591
Re: Where did the RPM's go?

No.. the boat is trailered..bottom is clean as a pin. Can bad gas cause this without causing a miss in the engine?
 
D

DJ

Guest
Re: Where did the RPM's go?

ae,<br /><br />I believe your top rate rpm is 4400 (maybe 4600). Anything over that is not good for the engine.<br /><br />Boats tend to gain weight, over the season. Gear added, bilge water, etc.
 
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