60HP Mariner revs fast, but prop barely pushes boat

1

123roger

Cadet
Joined
Aug 28, 2011
Messages
14
Was running fine and cruising at about 20 mph (3800 rpm) then the engine reved to 5500 and forward motion almost stopped. Seems OK at low speed/low rpm but as soon as you reach about 2300 rpm's it does it again. Had to limp back several miles to the ramp today at a VERY slow speed. Oil level in lower unit is full. What could cause this?
 
6

62 ROYAL SCOTT

Petty Officer 1st Class
Joined
May 29, 2011
Messages
280
Re: 60HP Mariner revs fast, but prop barely pushes boat

:)HELL-O 123roger YOU SPUN YOUR PROP [THAT'S WHAT I THINK ]I'am just a cadet:(
 
1

123roger

Cadet
Joined
Aug 28, 2011
Messages
14
Re: 60HP Mariner revs fast, but prop barely pushes boat

I removed/reinstalled the prop a few minutes ago...it "looked" ok to me, but when I reinstalled it, the nut might have gone on a couple more turns. Could it just not have been tight enough? Any out of water way to test this?
 
1

123roger

Cadet
Joined
Aug 28, 2011
Messages
14
Re: 60HP Mariner revs fast, but prop barely pushes boat

After removing the prop again, the splinned motor shaft and mating prop splines are all perfect..so there was no way the prop was slipping/spinning on the shaft. With the boat NOT running it turns easily in nuetral....putting it in forward or reverse it is extremley had to turn....What could have been happening on the water today?
 
bgc

bgc

Ensign
Joined
Jul 13, 2011
Messages
980
Re: 60HP Mariner revs fast, but prop barely pushes boat

The prop has a rubber bushing around the splines, this is in lew of a shear pin. Swap prop.
 
C

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 60HP Mariner revs fast, but prop barely pushes boat

The rubber hub between the prop and the spline coupler has begun to slip at high HP.

Remove the nut, draw a line across the hub from the inner coupler to the outer prop, replace the nut, run the boat til it happens, then remove the nut and see how the line is not lined up, it slipped.

Take it to a prop shop and have a new hub pressed in.
 
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