Crack and Water Leak at Prop Shaft Strut - Fiberglass Repair

[dpskier]

This is my first post. I was wondering if anyone could add some insight on best practice to perform a DIY fiberglass repair.

I purchased a 1990 Ski Nautique right at a year ago. I spent the spring and most of the summer rewiring the dash and a multitude of other things to seemingly get it water worthy, so I really only had it on the water a hand full of times last year. I noticed the bilge filling up with water... not a terrible amount, but more than what I thought was reasonable. I didn't want to leave it on the water overnight, as I wasn't sure if it would be floating in the morning. Now that the weather has broke, I filled the bilge with water to see where it might leak out, and located some cracks at the prop shaft strut. Photos are attached.



Based on some internet research, my plan is to grind out the cracks from the bilge, and do the bulk of the repair from the top side. I was thinking of using West System epoxy, but am unsure on whether to use mat or some other fabric, or some specific combination of the two, or how thick to make the repair. I was then going to do a thin repair on the bottom side, again with West System epoxy, and some sort of filler, and the touch up the gelcoat.

Does the above sound reasonable? Should I consider a poly resin, especially on the underside? Any pointers on glass material to use? All help and information is welcomed.

Thanks,

Dan

[Nautiquehunter]

Is there any vibration when running kinda looks like the strut was stressing the hull?

[dpskier]

The prop was bent when I bought the boat, and there was a vibration then. I had the prop straightened and checked the shaft for run-out, and it was great. The vibration totally went away when the prop was straightened.


I have to assume the previous owner hit something fairly solid at some point in the boats life. The leak is probably "bearable" to some degree, and I am guessing they just lived with it.

[bignicolet]

Are you 100% sure the leak is coming from that area?
About 10 years ago I hit a stump with a masterRaft and it bent the strut, and the prop. I took it to a dealer to check and they told me the shaft was not bent and I only needed to replace the prop and the strut. The pictures you posted look like a similar job where the strut was replaced and that silicone job doesn’t look like a dealer or factory job. In my case I had a leak to however after living with it for several seasons I spend some time inspecting while in the water and found it to be coming from the rudder area. If you are not 100% sure of the location of the leak check around the rudder shaft seal as if you hit something large the rudder probably took a good impact as well and may have unsealed or damaged the fittings.

I did the repairs in my driveway and was able to get the leaks fixed without any major fiberglass work, just loosening and resealing/replacing anything damaged. I learned that you can replace the shaft strut without removing the shaft very carefully, it does require some heat and a lot of pry bars etc.

Good Luck!

[dpskier]

I filled the bilge with water and elevated the front of the boat. It is possible I didn't have enough water to show all possible leaks at the rudder, though I am sure the bottom of the rudder was submersed in the bilge. The leak I found was dripping water through a crack at the rear of the strut, and the sealant around the strut was not wet. I guess, I am sure there is a leak through the hull at the strut. I think once this is patched up, I need to get the boat in the water without the rear seat to double check the rudder as well.

I may be able to just repair the top side. I just want to be sure to do it correctly. I would hate to go through the effort, and leave a problem later for myself or the next owner.

Dan

[bignicolet]

Dan

I would get an opinion from a boat fiberglass shop. I did have some gel coat damage below water line and was told by the body shop that repaired it that the fiberglass can get waterlogged. I don’t know if this would degrade the structural integrity of the boat. The third picture of the water drops you posted appears to have drops in the crack as well as the rear of the strut? Are you sure that there is no leakage coming from the bolt holes for the bolts connecting the strut to the boat inside the boat? If you are pouring water on the top side the sealant should protect both ways, however, the sealant is all applied to the bottom of the strut. You may want to consider removing the strut bolts/nuts and seeing if you can lower the strut from the hull to inspect and potentially clean the hull & bottom of the strut.

You can remove the strut bracket, you will need some heat and be very careful with any pry bars, the damage you have now may have been from the previous owner doing that when removing the last strut bracket. The good news is you don’t have to remove the shaft to do this. I can tell you from experience that it is not an easy job as the silicone creates a glue like bond. If you can remove the strut you can likely see the extent of the gel crack and repair and reseal it correctly.

Good Luck