Sea Nymph, Grumman, and Lowe all had issues during the OMC years with corrosion caused by the wood they used. They were using marine plywood that contained cupric sulfate which corroded the aluminum.
Pay special attention between the transom wood and outer skin.
IF its been bottom coated, make sure that coating does not contain copper, that too will eat at the aluminum.
It sounds like you may be looking at sanding and stripping down a good bit of the hull?
Small holes can be filled with JB Weld, using it much like common body filler. Slightly dimple the area, rough it up with course sandpaper and coat with JB Weld, Marine Tex, or any similar epoxy. Always paint over epoxy since it naturally has little UV resistance.
Some pics would help too.
When it comes to the ocean, in my opinion, most smaller aluminum boats are just too light.
I've had my 16ft out a ways but never out of sight of land and only on very smooth days with no storms in sight.
Wide and deep is the ticket, but in the end its about displacement and freeboard.
The Ocean can produce huge waves without warning and a light, shallow hull will do one of two things, either it rides the wave and stays on top, or it swamps and capsizes. It helps if you have enough power to stay on top when running in rough water. If you can't keep up with the waves, your more likely to get swamped.
I had a buddy who fished way out off shore with a 15ft trihull for years. We never knew where he was going and never took anyone along. (He was 80 then), then one day his wife called and said he went fishing but never came back when he had said he would. He was four hours late by then. After some digging through his stuff in his garage we found a note book where he was marking where he caught certain fish, we got hold a buddy with a 35ft center console that had a modern radar system and we went out searching. We found him 33 miles offshore drift fishing while tinkering with his motor that failed to start. It turns out his fuel filter, which was a screw on style, had rusted through, and he couldn't get fuel to the motor. He had run the battery down trying to start it and had resorted to pulling the V4 Evinrude over with a rope that he made by stripping down a piece of his anchor rope.
I spent 20 minutes in his boat that day by passing his fuel filter and getting his motor running so we didn't have to either tow his boat or abandon it there. Once running we followed him back into the marina where he launched. The guy was insane when it came to big waves, he would crash waves like that little thing was indestructible. We watched him the whole way in pounding that boat as hard as he could the whole way. It had hull cracks with patches all over it, broken seats, two or three layers of plywood on the floor and was likely water logged from years of being outside without a cover. being a bow rider didn't help it any out there either as every drop that came over the bow ended up in the boat. To his benefit, he did have four 1,500 gph bilge pumps in it but if he ran them all the battery and charging system couldn't keep up.
He ran that boat a few more times after that but I think his wife's nagging put an end to his crazy fishing trips, and the $480 fuel bill my buddy handed him for going after him that day.
He's long gone now but he apparently regularly was running that 15ft boat out that far and even further. When he passed his wife asked me to get rid of his boat, when I brought it home to cut it up, I found more of his notes and compass headings and he had points marked over 100 miles off shore.
He had put two 60 gallon fuel tanks in the boat, one on each side, combined with the factory keel tank that held 40 gallons. The two added tanks were built into seat boxes on which both seats were mounted. the lids were reversible by simply lifting them off the tank and turning them around so he could fish facing rear ward. He had a shelf that would fold out on the port side that would turn the right tank box into a place to lay down and sleep. Apparently he'd set his lines and take a nap out there in a 15ft boat. No telling how long he had been doing it but the boat was a 1971 model, and the he had pictures of a 1950's even small, MFG on his garage wall.
