lower unit slipping

B

bill0737

Recruit
Joined
Apr 1, 2005
Messages
2
I have a 2001 50hp mercury on a 20 ft pontoon. Both were bought new in 2002. When I try to accelerate the motor revs up but the prop does not drive the boat, it slips like it is out of gear. Pulling the throttle back to idle position re-engages the drive. Sometimes when I'm going at cruising speed and hit a small wave it will do the same thing and I again have to pull the throttle back to re-engage the drive. Any ideas ?
 
M

Moody Blue

Captain
Joined
May 24, 2004
Messages
3,136
Re: lower unit slipping

Sounds like a spun hub on the prop. A rubber insert connects the outer prop housing to the inner splined housing. When the prop strikes something, the hub is supposed to break free to protect the drivetrain gears. When under low load everything will appear fine but when you apply a heavier load the inner splined housing will spin inside the outer prop housing. To check this, put an alignment mark on the hub and outer prop housing. Take the boat out for a run. Recheck the alignment mark. If they are no longer aligned then you have a spun hub. Easy and inexpensive to fix at most marine shops. Good luck.
 
7

700XC

Cadet
Joined
Mar 26, 2005
Messages
21
Re: lower unit slipping

If you put your motor in Fwd gear (not Running and on Shore) you bshould not be able to turn the prop if you can do as rob sugests.<br /> You could also have a problem with your shift alignment / syncro and you are not engaging the lower unit fully into Fwd. gear. <br /> Question ?? you are not having cavatation problems are you,,,, prop spinning in the water eg. sucking air down to the prop from the surface of the water Just checking. If your shifter cable needs adjustment get it done soon and do not keep running in this cond. or damage will be imenit.
 
B

bill0737

Recruit
Joined
Apr 1, 2005
Messages
2
Re: lower unit slipping

Thanks to RodC & 700XC !<br />I won't be able to check these things out until May, when the Pontoon goes into the water for the season. I keep it at Higgins Lake and store it at a marina up there. I'm not sure what cavatation is but from your description I don't think so. At low speeds it runs fine and if I accelerate slowly it gets up to 16-18 mph (5,000 rpm) and will plane out sometimes but won't go for very long before it disengages. Sometimes it just starts slipping (prop disengages from gear, doesn't drive boat and motor revs up) when I accelerate quickly.<br />Thanks Again,<br />Bill0737
 
You must log in or register to reply here.
Top