Have a regular 377 in a 247 islander weighs 4,000lbs. The reg 496 weighs 400 more lbs and offers a .7 better power to weight ratio. Is that worth the extra weight? How big a difference in top speed/boat performance does .7 make. Again, new to this, please just helpful advice.

I googled both engines to get their weight. Thank You for your response. I bought this boat, and thought it would top out higher, Im maxing out at 45 mph with a full 80 gallons of fuel. A guy I know to me it was “A Lot of Boat for that motor” insinuating performace is not optimal. Just wanted some insight.

Islanders are super bow heavy compared to the cuddy models, so extra weight in the stern actually helps balance it out. Do you have the Bravo or Alpha drive?

Bravo Drive

I’d put in the bbc without a second thought. If you’re in fresh water find one with aluminum heads, manifold and exhaust and you’ll be pretty darn close to a sbc.

I swapped out a lot of cast iron for aluminum on my 272 Islander with the 502 and still looking for a prop with enough bow lift to compensate for the weight loss.

[QUOTE=flashgordon;4706720]Doing a quick google check sbc is 575 and bbc 685....

and there is no substituent for cubic inches accept for cubic dollars

the bbc is already one step above a sbc to start with....[/QUOTE
You are absolutely correct, something isn’t right! That is what has made me start thinking engine swap. As I’ve had it out, first I got an emission fault and engine went into guardian mode. O2 sensor was fouled. Replaced it, took it back out, got a Fuel System Fault and engine went into Guardian mode. Its currently in the shop again.