Proper torque on prop nuts

Play'N Hooky · 01-20-2010, 11:14 AM

I am installing the props onmy project boat and was trying to determine the proper torque for the prop nuts.The boat has twin inboards with 1-1/4" stainless steel shafts (7/8" prop nuts).The manual says to consult the manufacturer for proper torque specs but I have not been able to get any info from Silverton. I referred to a standard torque spec table that Ilocated in some engineering reference materials thatI have and it says for 316 stainless 7/8" bolts with 14 threads/inch that the dry torque should be about 200 ft-lbs. I've put a light coating of anti-seize on the shafts so I was going to reduce that by 25% (~150 ft-lbs) as recommeded for "wet" torque specs. Am I in the ballpark on this?

Thanks

Alan

Tuna Man · 01-20-2010, 12:22 PM

On a MercCruiser Alpha Drive........

Torque to an initial 55#. Then continue until the lock tab can be bent in place.

Sequoiha · 01-20-2010, 01:49 PM

Ron is correct on alphas,,, i torque outboards to 40 ftlbs....

Play'N Hooky · 01-20-2010, 03:24 PM

Thanks for the responses gentlemen. I know onmy outboard the torquerequirement isn't that high becausethe prop is resting on the thrust washer and the shaft is splined. But in this case, the shafts are smooth tapered with a key, so I figured the torque requirement would be higher. I snugged them on pretty good last night and the props were still moving up the shafts a little with each turn of the nut. I didn't want to over do it so I stopped until I could consult with theexperts.

Thanks

Alan

The Maintenance Shoppe · 01-20-2010, 04:03 PM

inboards, transmissions, 1.25" prop shaft. torque prop nut to 125-150 ft lbs. Do not use anti seize in threads, use marine grease.

Play'N Hooky · 01-20-2010, 04:45 PM

Quote:

TMS (1/20/2010)inboards, transmissions, 1.25" prop shaft. torque prop nut to 125-150 ft lbs. Do not use anti seize in threads, use marine grease.

Thanks for the response. Well, as it turns out, when I said "anti-seize" I meant "OMC Trailer Bearing Grease" because that is what I actually used on both the prop shafts and the prop nuts. I just wasn't sure that was appropriate.

Thanks for all ya'lls responses.

Alan

01-20-2010, 11:14 AM	#1
Play'N Hooky Senior Member Grouper Join Date: Sep 2007 Location: Andalusia, Alabama Posts: 947	Proper torque on prop nuts I am installing the props onmy project boat and was trying to determine the proper torque for the prop nuts.The boat has twin inboards with 1-1/4" stainless steel shafts (7/8" prop nuts).The manual says to consult the manufacturer for proper torque specs but I have not been able to get any info from Silverton. I referred to a standard torque spec table that Ilocated in some engineering reference materials thatI have and it says for 316 stainless 7/8" bolts with 14 threads/inch that the dry torque should be about 200 ft-lbs. I've put a light coating of anti-seize on the shafts so I was going to reduce that by 25% (~150 ft-lbs) as recommeded for "wet" torque specs. Am I in the ballpark on this? Thanks Alan

01-20-2010, 12:22 PM	#2
Tuna Man Senior Member Grand Slam Join Date: Oct 2007 Location: Calera, AL....25 Miles S of Birmingham Posts: 6,581	RE: Proper torque on prop nuts On a MercCruiser Alpha Drive........ Torque to an initial 55#. Then continue until the lock tab can be bent in place.

01-20-2010, 01:49 PM	#3
Sequoiha Senior Member Sailfish Join Date: Sep 2007 Location: Pensacola Florida Posts: 2,478	RE: Proper torque on prop nuts Ron is correct on alphas,,, i torque outboards to 40 ftlbs.... __________________ Kenny Mann Ms Penny Fishing Team Member NRA 172499461 Minn Kota ASC Dealer for The Super Stick www.thesuperstick.com Emerald Coast Marine LLC Allmost Anything Computers 4610 Saufley Field Rd Pensacola Fl, 32526 1-850-456-8196 1-850-455-8318 Sequoiha@cox.net Kenny_Mann-ECM@cox.net

01-20-2010, 03:24 PM	#4
Play'N Hooky Senior Member Grouper Join Date: Sep 2007 Location: Andalusia, Alabama Posts: 947	RE: Proper torque on prop nuts Thanks for the responses gentlemen. I know onmy outboard the torquerequirement isn't that high becausethe prop is resting on the thrust washer and the shaft is splined. But in this case, the shafts are smooth tapered with a key, so I figured the torque requirement would be higher. I snugged them on pretty good last night and the props were still moving up the shafts a little with each turn of the nut. I didn't want to over do it so I stopped until I could consult with theexperts. Thanks Alan

01-20-2010, 04:03 PM	#5
The Maintenance Shoppe Senior Member Snapper Join Date: Nov 2007 Posts: 532	RE: Proper torque on prop nuts inboards, transmissions, 1.25" prop shaft. torque prop nut to 125-150 ft lbs. Do not use anti seize in threads, use marine grease. __________________ *The Maintenance Shoppe* Full service boat, pwc, and trailer repair 4048 Creighton Rd Pensacola, FL. 850-221-6789 www.themaintenanceshoppe.com

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