You can weld on the boat in the water
. I use a 6 KVA petrol generator
. Mig and stick are useful depending on what you are doing. Stick may seem harder, but if you end up with a good looking weld the chances are that it will be structurally sound. With a mig you can have a lovely looking weld which may not have much penetration and therefore not much strength. This is especially true with gasless mig - I would not use that at all.
Your best bet is to go and do a short course on both types.
As far as tools , buy a needle gun, a hand held sandblaster ( the sort that sucks grit out of a bucket - never use anything but proper grit ) and a compresser with enough capacity to run those tools. Be careful of chipping inside under the waterline!! Also useful is a self darkening welding helmet and some disposable earplugs.
I would not hire, as it looks like you will have hours of work so the tools will pay for themselves. Have a look on TradeMe for second hand gear
Another good investment is a filtered airsource for yourself - you will be making lots of dust. 3M sells good gear
, with a fan unit on a belt and a full face helmet, they are expensive but so are your lungs and eyes.
You will need to check the entire hull
from the inside, even if it entails removing panelling to do so. Maybe one of those borescopes that you can connect to a laptop
may be useful.
If you find rusty areas, try to work out why they rusted. You my be able to re design to avoid water
The good thing about steel
is that the repair should be as strong as the original, and if you do it properly the boat should be trouble free for a long tome.
I am inspecting Nekeyah completely for the first time in 25 yrs and am finding very little of importance so far. The hardest part is destroying timberwork to get at things.