I have used both Kreem & Red Coat with good results.
Red Coat is in this tank. I also had Red Coat in one of
the motors I ran last year. It was on the boat for over
5 weeks without any issues. I think they all work if
the tank is clean and etched properly. My experience
is mostly with aluminum tanks sealing up cracks. I
usually give them 2 or 3 coats hoping it will hold them
together, keeping the cracks from spreading. That
might be wishful thinking on my part.
Tubs.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.