posted 01-27-2014 01:45 PM ET (US)     

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1998 Outrage 17

Should these bolts on the trolling motor mount bracket be replaced? If so, any recommendations?

Transom view
http://www.flickr.com/photos/picflight/12176094935/
Inside view
http://www.flickr.com/photos/picflight/12176091955/

posted 01-27-2014 02:54 PM ET (US)         

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No, not kidding at all.

I am not sure given the condition they are in if replacement and resealing is recommended, hence my question. To replace and reseal will not be a quick process to do it right.

posted 01-27-2014 06:13 PM ET (US)            

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Those cap screws (bolts) and nuts do not appear to be stainless steel. I'd replace them with stainless steel.

Yeah, about $10 worth of hardware at the local hardware store.

There is no such thing as stainless steel Grade 8. You donot want to use Grade in this application because it will rust

posted 01-28-2014 11:43 AM ET (US)            

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Tom is absolutely correct. Use stainless steel bolts.

Beware of cheaper stainless steel bolts, they are not graded 18-8. These cheaper A-2 stainless bolts will rust in saltwater applications due to the difference in alloy, and they have much less tensile strength. I have seen a lot of these A-2 SS bolts being sold cheaply at big stores, but most of them will have an "A-2" stamp on the head. If the bolt is too cheap in comparison with a known 18-8 bolt, it is probably an A-2.

posted 01-28-2014 10:25 PM ET (US)            

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If your local hardware store does not have what you need, you can order online. I really McMaster-Carr as a vendor:

http://www.mcmaster.com

McMaster-Carr offers both 18-8 (aka Type 304) stainless steel, which is what the hardware store will have, and type 316 for about twice as much.

posted 01-29-2014 05:29 PM ET (US)         

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I sprayed PB-Blaster and loosened the nuts from the inside of the transom. I was shocked to see that the nuts were just a tad tighter than hand torqued. Two of the bolts are on a slightly curved surface, so I can understand that they cannot be tightened too much risking cracking the gelcoat.

Is this amount of torque normal for transom mounted trolling motor brackets? I am guessing that majority of the engine weight is being carried by the flat bracket resting on the transom.

posted 01-30-2014 12:43 PM ET (US)            

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That area of the hull has foam inside, not solid wood backing. The weight of the motor on the bracket has probably just compressed the hull enough to allow the nuts to be loose.

The old washers are much too small. When yo buy new washers buy "fender washers" which have much larger external diameters.

The curvature of the hull should be dealt with. I'd buy brass bushings and then cut and/or grind them to the angle of the hull. Place those on top of the fender washer and the nylock lock nuts on top of the customized brass bushing.

posted 01-30-2014 01:32 PM ET (US)         

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@Tom,

Thanks for the details.

Any particular reason you mention Brass bushings? The area between the inner and outer diameter should be large enough to take the load compressing against the hull.

Are these the kind of bushings you had in mind?
http://www.ebay.com/itm/ BRONZE-BRASS-BUSHING-3-4-ID-AND-BIGGER-ALL-IN-STOCK-/ 120651624791?pt=LH_DefaultDomain_0&hash=item1c1765b157

So, if I got this right, hull, bushing (matched to hull curve), fender washer, lock nut?

posted 01-30-2014 01:53 PM ET (US)            

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Brass is easy to cut and corrosion resistant. Stainless steel and bronze are fine too, but more difficult to work.

http://www.mcmaster.com/#unthreaded-brass-spacers/=qh8opo

It not the load compressing against the hull on the outside, it the pulling force of the two upper bolts on the inside of the hull that tylically crush the fiberglass there.

Larger and more even washer surface area = less force/area and less chance of dimpling the fiberglass.

posted 01-30-2014 02:18 PM ET (US)            

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You can even buy type 316 stainless steel spacer bushings with an angle already in them. But the angle is a straight 45 degree angle so you would still need to grind them on a bench grinder to get them to fit just right.

They also cost about twice as much.

http://www.mcmaster.com/#unthreaded-spacers/=qh902e

posted 01-30-2014 02:46 PM ET (US)            

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quote:

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So, if I got this right, hull, bushing (matched to hull curve), fender washer, lock nut?

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I believe the proper sequence will be: Hull, Fender Washer, Shaped Bushing, Lock Nut.

This way, the fender washer will bend to the shape of the hull, and the bushing will reconcile that angled shape with the nut, which remains perpendicular to the bolt shaft.