When I replaced both tanks (160 gals each) (35' CT Trawler) we had to remove both engines, hung them in the salon on an "A" frame, one at a time, removed old tank, installed new tank, reinstalled the engine, then on to the next tank, same process. Cost was around $12,000. 8 hours to take out each engine, 11 hours to reinstall each engine @ $85. per hour. Balance of the costs where tanks, parts, hose, fittings and the actual labor to remove old and install new tanks.