prop slipping? how tight should tighten??

[georgiaboy]

I just went out in my boat and had a problem. I have a Mercury Classic 50 on a 16' Bass Tracker which is 5' wide. when I got up to speed the rpms were fluctuauting all over the place and boat seem to remain at same speed. I just had prop rebuilt and I was not sure how tight to tighten the nut but since it is on a spline I would think it could slip. The prop is a 10 1/2 X 14 which normally would run about 5400rpm I think. The motor is plenty deep enough in the water so I do not think that is the problem. I am going to mark prop tomorrow to see if it slips. Any other ideas and how tight do I tighten the prop bolt?

 

[Gary H NC]

Re: prop slipping? how tight should tighten??

Not sure of the torque setting on that outboard but marking the prop and testing to see if the hub is slipping would be your best bet.The prop hub should not slip on the splines at all.

 

[Bondo]

Re: prop slipping? how tight should tighten??

45/50ft.lbs. is Plenty,.....

The Nut only holds the prop On when in Reverse....
In forward, it's held by the Splines,+ the Thrust.........

 

[Texasmark]

Re: prop slipping? how tight should tighten??

My manual for a Merc 90 says 55 ft-lbs. So the 45-50 sounds good to me.

Like you said, a slipping hub surely can cause it and the nut has nothing to do with that in regular rubber bushed props. Some of the newer props with user replaceable hubs require specific torque.
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On a different note, I was rummaging around in the shop yesterday and came across a tin of shear pins (your reference to splines on the shaft....shear pins were used with a slick shaft)..........remember those pesky critters?

Only failed when you were fishing the winward side of rip-rap and you couldn't get to the paddle to push off the rocks in time.....yucko.
Then you had to reach back across the engine to get at it and you always dropped something in the water or the wind turned the boat around and you were taking water over the stern..,.....or you had the spares in the other tackle box which is at home. Grrrrrrrr.

That one thing put me into the Merc camp....now that I'm there I like a lot of other things they do too. Course everyone runs splines today on engines of any size. Seems OEM's finally came to their senses.

Mark