Repairing a Corroded Hull

[Katoh]

Hello To All
While searching for materials, for my larger build I have taken on a second project. I purchased an old Fisher Marine 5.9 plate alloy boat already with in inboard diesel 20' cuddy. Could not resist buying as the price was right. On inspection there's a bit of corrosion in only the bottom plates mainly around the keel bar, with a few spots up further towards the chine on both sides around mid-ship. Top plates, cabin, transom, and bow show no signs or very little of corrosion. It has a fully welded checker-plate floor which does not make life any easier.
I plan to remove the hull from the trailer, remove the motor and the stern drive leg, and use a turbo nozzle on a high pressure water plaster to remove the paint on the bottom and top plates and transom. The water pressure will have enough power to Peirce the hull in badly corroded areas (I Think).
Would I be advised to remove the floor?
For small pits and holes, what method of repair would you recommend?
For say holes over 1/2" wide or a section of badly pitted plate what would you do?
I prefer to weld then use an epoxy filler.
thanks
Katoh

[Katoh]

Sorry forgot to mention, I do not have access to a TIG but have a 275amp MIG with a 250amp Spool gun dedicated for aluminium only.
Cheers
Katoh

[tazmann]

I'm no expert but have done some aluminum repairs. I would say first have a look under the welded in floor to see what shape it's in, rather than cut the floor out drill a few holes with a 3 or 4 inch hole saw, in a way that you could weld them back in if all is good.
Tom

[Katoh]

Thanks for the reply tazmann, that's not a bad idea. When you did your repairs, what did you do with pits and small holes. I thought I would just give them a zap with the mig to fill them in then grind them down flat.
Katoh

[tazmann]

Katch
If the pitting is not to bad welding them up should work fine. after cleaning grind the corosion out with a rotary file clean again and weld it up.
Tom

[Katoh]

Thanks Tom, What would you do with larger pits say were you end up with a 1/2" hole? Just weld them in or put a backing plate behind them and then weld them in?
There is two anodes on the leg should I put one on the hull as well?
Katoh