Re: Fuel tank longevity
Our C37 is a 1980 and we replaced the tank around 1990 because of seepage due to corrosion. The older installations had a single walled tank sitting on a piece of 1/4 plywood which sat on top of the keel bolts--essentially a battery after you add enough seawater. I agree with the other post that a dryer bilge would have prevented or at least delayed this process.
Our replacement tank was made by the original supplier in Huntington Beach but had a double thickness of aluminum on the bottom. Robin (Thumper's predecessor in SoCal) recommended putting schedule 80 PVC pipe in the bilge for the new tank to sit on which we did. I also put PVC caps on top of the keel bolts just in case the PVC ever collapses. I etched and Alodined the bottom 1/4 of the tank and put 4-5 coats of WEST epoxy on thickened with Aluminum powder. I'd go with a Rhino coat these days.
After 20 years it would be worth having a look at the bottom of the tank and insuring it is not in contact with the keel bolts. If you are not living aboard you could probably lift the tank out and set it on a drop cloth in the salon to Rhino coat it. Otherwise it does fit through the sliding hatch, at least ours did.
1980 C37 Yawl #22