Tracking fins stripped

My nautique's tracking fins have a few screws that are stripped. What do you guys suggest i do?

The screws were very loose when i checked them earlier this summer and seemed like they were barly grabing. So i took some sylacone and filled the hole and then put the screw back in. They held the rest of the summer but I was wondering if i should get longer screws or something else like go all the way through?

Im not familar on how tracking fins bolt on since I dont have them. Is it a sheet metal screw in the fiberglass, or is is a tapped hole into something? This just has me curious!!

On the three I've done, all were screws into the reinforced fiberglass down the center of the boat. Going into the first, I was expecting thru bolts, or at least tapped
holes, but that was not the case.

BKH

Is it possible to use a ss flat heat machine screw where you can drill and tap and install ss thread inserts (helicoil). You might need more than one insert if you have enough depth. They work amazingly well in soft aluminum, but honestly, I have never tried it in fiberglass. If theres enough depth for enough threads, it should work, but I cant be certain. I do know that on a fiberglass antenna mount we use, they tap 5/16-18 about one inch(with no helicoil) in the fiberglass, and I can tighten it down to the point of bolt failure. I would use a course thread if I were to try it. Any one else have any input to this??

I agree that thru bolting is way to go if access is available to tighten them!!

I dont like the sound of through bolts now. I think i'll stick to screws. I think i'll look for a wider screw.

Jeff,

Not vouching for the accuracy, just reporting what I've been told. Like I said, some companies do through bolt (I believe the older Malibus and Centurions did so, but I'm not sure).

Physically, I think there are differences in the forces of an object hitting the prop/rudder/shaft. The shaft is angled
over a 1 or 2 ft run. If never seen a shaft
ripped out, but I have seen them bent up.
The prop will sheer off before it'll rip a hole in the boat. I suppose the rudder could rip a chunk out, but I've not seen it. Instead, the round portion of the rudder tends to bend or sheer.

The Fins on other hand, are pretty much an immovable object, dead center, and typically right under the heaviest portion of the boat. If you hit something with them, you hit solid. So I think the theory is that the bolts will stay with the fin and rip a big section out of the bottom of the boat. With the screws, there is a better chance that the screws will be ripped out of the fiberglass. This would cause some damage to be sure, but not as severe as if a big section were ripped out.

The fins really shouldn't loosen up. They use very adhesive, as well as the screws.

In any case, CCs, at least the more modern CCs, use screws. BKH

I personally have seen the hull damage from having them thru-bolted, Sheared the front 2 bolts, peeled the fin back and ripped the back 2 thru th hull. Big hole, major water leak! Luckly it was VERY close to a privte boat ramp and was able to be grounded on it before it took on to much water. I am sure the hull must be thicker at the shaft/rudder aera. Just like David's advice I would fill the old screw holes with foam rubber and reisn, or maybe epoxy, wait a few days to dry, reinstall the fins in new holes putting some 3M 5200 on the either stainless or bronze screws

WOW!
I have been following this discussion and have found it to be quite enlightening. I do agree screws are the way to go.I am sure that 99% of the times that fins come off, it will be the result of striking imovable objects. Your prop, rudder, prop shaft and strut are going to be scrap metal a few hundredths of a second later.

I have only one question for Mr. Mars. Whatever pocessed you to check the screws on your fins anyway? In retospect I guess it was a good idea.

Trike,

Certainly wouldn't surprise me if through bolt was the standard in 80. Good to know.

BKH