Fixing a Hole

[MarinUS]

Dear fellow sailors;
My OMC Saildrive
needs to be removed from my S2- 8.0 B sailboat because it’s old (1983 model and I just don’t trust a gas engine below deck.
The plan is to stick a 9.9 four stroke outboard on the back.
My question is; how many layers of fiberglass I need seal the hole where the saildrive lower unit protrudes through the hull. The plan is to use epoxy.
Next question:
Should I seal it from the inside, or from the outside?
Thank you.
Marck.

[Fore and Aft]

From the inside is easier, I like to find some Laminex or similar material with shiny surface to attach to the outside of the hull so it acts like a mould. I usually use polyester on the inside and make it as thick as the hull. Then the oustide I glass with a layer of 450gm double bias in epoxy. Using polyester on the inside means you can use flo coat to paint the inside of the hull. It also lets you use chop strand and some heavy woven rovings. You should be able to get the repair flush with the hull so you can not even see it was there.
Its a bit hard to describe but I mould the laminex over the hole, then from the inside glue another peice of laminex the exact size of the hole onto the mould. That way when you remove the mould you have a 2mm indentation. So then you grind the exterior hull 100mm around the the hole to match the indentation and cover with one layer of epoxy/fiberglass and peel ply. Then it is basically a bit of epoxy filler and a quick sand.
Cheers