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Beginner question on 377 v 496
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. |
Originally Posted by ericmartinez1
(Post 4706612)
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. |
Originally Posted by Trash
(Post 4706616)
I'm not sure where you got the 400 lb weight difference. I think it's closer to 100-150 lbs. regardless, I believe too many people over think the weight issue and under think the torque advantage of the big block. It will generally make more torque at a given rpm compared to the small block. I love small blocks but the big block will almost always have an advantage in the marine environment.
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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. |
BoatTest.com shows it runs 60mph with a 375hp 496mag.
Even with your 320hp, you should still be running around 55mph, so something is not right. |
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.... |
Originally Posted by flashgordon
(Post 4706720)
and there is no substituent for cubic inches accept BOOST |
[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. |
Originally Posted by underpsi68
(Post 4706728)
I fixed it for you :circle:
ahhhhhhhhhh,,,i like it boost good one.. |
Big Heavy Vee's need Big Blocks. The 496 in stock form is almost bullet proof. Boost aside there is no replacement for displacement.
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My 2002 29ft Sunsation will run 58 mph with a 377 in it, so i think you my have a problem. Prop maybe or just need plugs cap and rotor changed out.
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My last boat had a 496ho and it was flawless, never missed a beat. That said, I've read quite a number of complaints about sensors and guardian mode with them so don't be too quick to change your 377 because of a couple of electronic gremlins. Top speed sounds a bit slow, tell the experts here your prop size and peak engine revs, it may just need a different prop to get things moving faster. First thing I'd do is make sure you're getting all you can out of the current setup before spending money on an engine change. My 2 cents, good luck and welcome to OSO. :) RR |
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