Make sure your fabricator is in the boat tank business, meaning that they are epoxy coated on the outside at the shop and that they are built to UL certification and USCG specs.
Installation procedure is critical. PM me if you want to get info on how to.
If the boat is to be used for charter as an IPV, tanks will need to be 1/4" thick for your COI. Otherwise as a UPV or recreational 3/16" thickness will meet BIA, UL and CG, but baffles and other construction details will need to comply.
I had my 2 120 gallon tanks made for $2600 last year around this time. New aeroquip fuel and return lines, SS ball valves, SS fill fittings, Hold down straps, neoprene isolation strips and new deck fittings, fill hoses ran another $800. You cant marry your brass fittings into aluminum without SS interface fittings, so I went with all 316 Stainless on everything.
Structural materials also add up the job. Consider reinforcing the shelf under the tank that straddles the two stringers on each side.
To me $3K seems low for the whole thing without cutting som big corners.
I Did my project myself and total cost was about $6500 for everything after all was said and done, but it was done right. I had a teak cocpit to contend with which may have had a higher material cost than you would need to budget for fiberglass, but $3K still seems low. My labor was about 80 hr. Admit I'm slow. The shakedown was a horendous offshore run from Shinnecock NY to Cape May NJ in 30 kt wind on the nose with props coming out of the water at times...the last thing you want is your fuel tanks to jump off the stringers and fly around in the boat.
BTW Hatteras did one bad thing on some of the old boats which they could get away with, which was to rest the deck supports right on top of the FG tank.
You cant do that nowadays, so the aluminum tanks need to be chocked and strapped, as well as the cocpit deck supporting its own weight.
I've seen marina estimates for similar work in the $15K to $25K range, done properly.
Atlantic Coastal Welding in Belmar, NJ. makes good tanks, a very good job,quick turnaround, wouldnt hesitate to recommend them. They also madethe tanks for Capt Bob's 34C Magic Hat.
My boat originally had gas, repowered in 06 with 6BTA5.9M's but thats another even longer winded discussion. Good Luck!
