200 hp 1991 Merc outboard acting strange

J

jgauthier

Recruit
Joined
May 6, 2006
Messages
1
I inheireted a boat with a 1991 200 hp Merc outboard. The motor runs like a top and even looks new. I took it out for the first time and as I was powering up, once I got over 6 mph, it acted like it was in neutral and it would rev up, but not go anywhere. When I lowered the speed, it would run great again. The trim was all the way down, so it wasn't like the prop was coming out of the water. It doesn't have a shear pin like the smaller motors. It isn't like a typical power loss where it is sucking air, it doesn't bog down, but the rpms go up, like I was in neutral and revving the motor? Any thoughts would be appreciated.
 
M

MercFan

Petty Officer 1st Class
Joined
Dec 31, 2005
Messages
347
Re: 200 hp 1991 Merc outboard acting strange

Spun hub on the prop?<br /><br />Essentialy your prop bites so hard in the water that the drive shaft spins up and the prop doesn't keep up.<br /><br />Easy to diagnose.<br />Use a white marker or nail varnish.<br />Paint a line from the center of the drive shaft across onto the prop itself.<br /><br />Run it and let it do that "rev-up no speed increase". Stop, and inspect your mark. If the mark doesn't line up anymore you've got a spun hub.<br /><br />Just remove the prop and hub, go to your marine dealer and buy a new one. Pretty easy and pretty cheap
 
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