How much to tighten prop nut?

[BOWMAKER1]

I just replaced a 13.75 x 15 aluminum prop on my 2001 Mercury 125 on my pontoon. I got a 13.25 x 13 four blade Solas Rubex prop. I used the new thrush washer and the new retaining washer and nut, but when I tightened it down the prop would not turn unless I backed the nut off a little. When it does turn there is just a very slight wobble to it. I did put on the rubber ring around the front of the prop hub but I have not had one of the same kind of rubber hub that this prop uses and there were no install info. Should this be torqued down to any certain specs, or just tightened against the rubber hub until it will just barley turn freely? I have not been able to get on the water but hope to in the next few days and don't want to mess up a new prop or motor. Thanks for all the help that I am sure will be forthcoming.

 

[BobGinCO]

Re: How much to tighten prop nut?

According to the Mercury service manual for my 2012 115 4-stroke:

Place a block of wood between gear case and propeller and torque propeller nut to 55
lb-ft (75 Nm), aligning flat sides of the propeller nut with tabs on the tab washer.

 

[Frank Acampora]

Re: How much to tighten prop nut?

No matter how tight the nut is , the prop should turn freely. You obviously have an interference. Some brands of props would need some type of slight modification to fit correctly. They don't tell this in the application. I am not familiar with that particular prop and engine combination so I can not give specific advice. Check closely with the prop both on and off to see where the interference is and correct it or if not correctible, return the prop.

Also: Double check the prop numbers to be certain the correct one was shipped. Hey--They are human and can make "mistakes."

 

[lakegeorge]

Re: How much to tighten prop nut?

I just replaced a 13.75 x 15 aluminum prop on my 2001 Mercury 125 on my pontoon. I got a 13.25 x 13 four blade Solas Rubex prop. I used the new thrush washer and the new retaining washer and nut, but when I tightened it down the prop would not turn unless I backed the nut off a little. When it does turn there is just a very slight wobble to it. I did put on the rubber ring around the front of the prop hub but I have not had one of the same kind of rubber hub that this prop uses and there were no install info. Should this be torqued down to any certain specs, or just tightened against the rubber hub until it will just barley turn freely? I have not been able to get on the water but hope to in the next few days and don't want to mess up a new prop or motor. Thanks for all the help that I am sure will be forthcoming.

Ditto to what Frank said, the prop should always turn no matter how much you tighten it down. Something is not right with the set-up.

 

[Texasmark]

Re: How much to tighten prop nut?

The prop is supposed to fit against a thrust washer that is usually wedged onto the prop shaft since the prop shaft OD and washer ID have a sloping configuration and the slopes are supposed to be lined up. Then the washers and nut go on the rear. The pressure on the prop is between the thrust washer and the nut and as stated 55 ft lbs for the 90 and surely the 125 is the same.

When installing removable hub props you have to be careful in your selection of what you use as some have additional parts that don't come with the rubber slip hub types.

Mark

 

[jestor68]

Re: How much to tighten prop nut?

The Solas web site has a instructional video on how to install a Rubex hub/prop. You might want to take a look.

 

[BOWMAKER1]

Re: How much to tighten prop nut?

Well I sent off an e-mail to Solas Props and got a very nice reply the other day. It seems the problem might be the rubber band gasket thing. The reply said that is to help prevent ventilation, but that most Mercury motors don't need it. He also said that personally he only tightens prop nut down to 8 or 10 foot pounds of torque and then puts the lock tab on to keep it from moving. I haven't been back to the boat to re-install prop with out the rubber gasket but plan to soon. The lake is still to high and the ramps are closed and no loading docks are in yet, but I really want to see what difference this 4 blade Solas prop does make. Thanks everyone for the help!

 

[90stingray]

Re: How much to tighten prop nut?

I am betting the thrust washer is too thin allowing the prop to wedge in self into the case. Compare it to your old one. If different, I would try the old one. You should be able to tighten as much as you can and it still spin. The 4 blade should do nicely. Your lake is too high? I wish we had that problem here. Good luck!