1964 ski Nautique project

Unless the dirt is grease and oil.

I'm still a firm believer in poly resin for a boat that was built entirely with poly resin.

Don't see the point in messing with conversion layers.

This shows one of the places where gelcoat “puddled”. Since it is cracked like this everywhere else I assumed it should be taken down to bare glass as well.
As far as the repairs go, if using vinylester as a conversion coat for the gel is an acceptable process I would much rather use epoxy. I have a good bit left over from the stringers and it would be nice to keep from getting involved with another system for repairs. However, I will NOT do this again so if dealing with poly in going to make the finish last longer/better than I’ll do it.

Thanks for all the thoughts!

It may be worth looking into this Epoxy Gelcoat SG 715if you are doing all the hull again, I have been mulling this over as another way to go, by just tip and roller on then sanding back and polish, would cost more but may be easy to use once you have prepped/repaired the hull.
If we have it here in Europe it will be in the USA too, get a small amount and do a test area first..

Good luck with it.

Now I see all the hairline cracks.
Ethan,
Test a couple spots with the epoxy. Try it first undiluted to see how well it penetrates. If you can still see where the epoxy hasn't soaked in, thin it down and do a second spot. As mentioned by Joe, you can always go over the hull with some 6oz. cloth.

Again - on the cracks - there is no benefit that is going to be achieved by trying to join them together with some sort of penetrating epoxy. It will only penetrate the crack, then it will stick to the sides of the crack - which is an old brittle poly that not only cracked to begin with but also has now been exposed to years of additional weather to age them. I don't care about oil or dirt or what have you I know epoxy sticks to much but if you stick it to a surface that isn't any good what good will it do you?    If one wanted to fill the cracks they would first have to rout them all out and then fill them - that is not reasonable.    You are looking to leave it in place, you are looking to give the surface you are going to gel on something with some tensile strength along the surface because the gel is not reinforced and doesn't have much of its own. So you need to add a layer, it can be done with light cloth - which wets out easier and usually provides less additional weight but will leave a cloth pattern that adds to your fairing woahs. It can also be done with the product I mentioned earlier surfacing veil mat - which is intended for this application as it leaves a flatter surface than the cloth.   You should not use any kind of matt in an application like this with epoxy as it doesn't dissolve the binders and makes it hard to get the mat to follow the contours of the hull. That's only one of the reasons you should use the vinylester. The other is that you would need to put a vinyl layer between anyway and you then would have to ensure that no where in the process had you faired down to the epoxy layer... its a total pia and will provide no benefit but additional risks and cost.
Edit-
You could use polyester resin as well however - not quite as strong a bond - and not as good a barrier layer for something that may end up underwater and it stretches more and is not as resistant to stress cracking . The only benefit to the poly in this case would be cost... to the point that many boats are made with poly with the exception of the outer layer which is made with vinylester - for the reasons discussed above.

Lake Mitchell, just east of Clanton.   I am about 45 minutes south of Birmingham.

Well, just a couple more hours sanding and the hull should be ready for gel.. I'd take some pictures, but I don't think I can hold a camera up...

While waiting for fairing compound to set up, I've been working on some of the mechanical issues. In switching from the dearbo to the longer velvet drive, I shortened the prop shaft the difference. However, from the wear marks from the cutlass bearing it looks like the shaft has always had 2" overhang past the strut. The the total length is 53" now, but should I shorten it another inch? The prop is a federal 12x14 but I'll probably get a Acme later this summer if that makes any difference with hull clearance.