5.0, 305ci Mercruiser w/Alpha 1....vibration around 1500-2000 rpm

blueday

Cadet
Joined
Jul 14, 2013
Messages
19
Hey guys.....found something in the river 2 weeks ago. Still not sure what it was, boat lost speed and had a little 3 - 4ft rooster tail. I immediately shut it down, trimmed unit all the way up. Didn't see anything wrapped around or damage besides my aluminum prop was chewed up a bit, nothing was floating around in water.

Point is I now have a some vibration around 1500-2000 rpm. Does this in and out of water and with and without prop (I just installed a ss prop to replace aluminum). Doesn't sound like the motor is misfiring (I have a car background with building engines and so on). I wouldn't say the vibration is violent, enough to notice it's odd and can feel seating on cushion and putting your hand on side of boat. No strange noises or out of the norm clunking in and out of gear. Vibration disappears above 2k and no vibration under about 1500. No vibration when in neutral and engine is revd up.

Any advice/help where I can start looking at wod be great!
 

duped

Petty Officer 1st Class
Joined
Aug 26, 2009
Messages
307
Re: 5.0, 305ci Mercruiser w/Alpha 1....vibration around 1500-2000 rpm

Pull the drive, check the alignment. You'll need to buy or make an alignment tool to do so. Should be done yearly anyways. Many a vibration problem have been caused by bad alignments, and an object strike could very easily shift things around.
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,344
Re: 5.0, 305ci Mercruiser w/Alpha 1....vibration around 1500-2000 rpm

slightly bent propeller shaft
 
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