What has been the experience with the original steel fuel tanks on a 50-year old 38 Commander or similar? I see there is a description in the Files about how to install new aluminum tanks--is this a standard upgrade after a few years? The last thing I want is for the tanks to begin to leak. Can they be inspected for evidence of corrosion underneath? What are the supports - wood, fibreglass, steel?
I think a lot depends oh where the boat is used and if the tanks have been up out of the bilge water. My 1967 31 commander still has original steel tanks. My current 1973 410 Commander also has original steel tanks. Both boats live on the Great Lakes. No salt water.
I will add that two large Commanders around here have had a problem with tan colored sediment inside the tanks. May be an issue with low hours usage.
In this area (Great Lakes) the tanks typically rust on the inside more than the outside. I've had corrosion issues on 2 of the three boat's I've owned up here. Using ethanol fuel seems to be what causes it. My first boat a 79' Catalina 280 had so much corrosion inside the tank that the filers had to be changed every couple hours of use. When I bought my Commander I expected the same problem so the first big project I did was replace the tanks. To my surprise they came out perfect inside. The previous owner told me he only used nonethanol gas, so I believe that to be the major difference. My latest boat a little 1960 14' Glasspar also had internal corrosion, it had an aluminum tank. It wasn't terrible and installing a big filter kept it in line.
The only way to really check is going to be checking the filters for rust/sediment, you could send a small ca,era down the filler neck I suposed, but I'm not sure it's really nessisary.
The support structure on mine was all wood.
Replacing old tanks is inevitable.
However if you dont have much sediment and not leaking than use the boat until tanks begin to show signs of deterioration.
On a 38 I belive the tanks fit thru the lazerete hatch not requiring engine removal
During the restoration of my 1971 23' Lancer (a saltwater boat) I removed the original gavanized steel tank to sandblast it, regalvanize and reuse it. When removed from the boat it didnt look that bad (some rust around the ends of the tank). After sandblasting the tank it was scary looking. The rust aroung the ends of the tank actually went all the way through. The tank had also been rusting from the inside out. I replacee it with a slightly larger one made by Moeller Marine. I had to make a new tank cradle (made from marine plywood) since my new tank was slightly larger than my old one. I also had to made different hold downs for it. Moeller had many different shapes and sizes to choose from. I ordered it through Iboats.
Good luck and just remember that just because it looks ok does not mean that it is. I found this out.
I own a 38 from 1969 and when I bought the boat it had one original tank and one replacement. The boat was kept in the Great Lakes and both tanks had brown sediment in the bottom. This happens when a boat sits for a long time with fuel in the tanks that starts to break down. My boat had sat in storage for 10 years to give you an idea. I chose to replace them and glad I did. I would have them inspected and depending on the condition replace if necessary. If they have sediment in the bottom it will lead to other problems for the engines that is best avoided. Obviously if they are rusting to the point they might leak that is even more serious. Good luck.
On old galvanized tanks sediment also comes from the process of the internal galvanizing deteriorating. It is usually more of a whiteish powder.
I'm in the process of installing new tanks in my 35 right now.
I made a full size mockup right in place first.
My tanks have increased capacity over the old ones and have to be installed while engine are out but if you want to replace tanks with out removing engines then just make sure that your old tanks and or your new tank mock ups can be removed thru the rear lazerete hatch.