I owned a supercharged Lycoming 480. When I got it, the previous owner told me how good it ran, and after doing a leak down test, only one cylinder was any good. So, 4k later, new everything, pistons, rings, valve job, oil cooling nozzels ETC......It ran like a beast.....On the 2 barrell it would outrun most 0-540 boats, which was 2900 rpm's. then Id open it up to 3400 rpm, the supercharger boost would be about 11 inches, JR Jurgain says about 360 hp......700 pounds + torque this is the good........
The bad.....it is rated at 52 Gallon's of fuel per hour at take off, with my holley 650 double pumper,,,,the fuel comsumption was MORE, but you did not have to run it at WOT.....on a cruise my current IO-540 wil burn 5 gal., making a 20 mile trip, whereas my supercharged boat burned 13 Gal.
My engine was direct drive, the propeller adapter, which bolts to the crankshaft is VERY dangerious, cause the bolts break...this HAS happened..the modifications require compleat teardown and crankshaft/case machining bigger bolts to fix.
The cylinders will over heat if you stay in boost too long, causing rings to loose seal. Tuning, fuel delivery, special suprcharger seals, and the fact Lycoming stopped making these engines over 20 years ago are some reasons I run a IO-540 now.
