Help!!!!
07-19-2007, 09:38 AM
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Location: Sebago Lake, Maine
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31' Scarab power decisions
Here's my story. I have a 1989 31' Scarab Excel with twin 454 mags 365hp. The starboard engine has some issues. I really like the boat, but it's time to go faster. I priced the parts to get these mags up to approx 500hp. $9,000 each with headers. Plus I will have to go to hydraulic steering. The boat will run a little over 68 mph on gps with 23p 3 blade mirage. What speed will I see with 500hp and 4 blade props? Is the boat worth the time and money. I do my own engine work, alot of street engines, have not done a boat yet. Should I fix the bad engine and sell for something with a step. As I said I really like the boat and it is in great shape. Any ideas? Cheaper power? I don't know what to do!
Last edited by Screamin' Seamen'; 07-19-2007 at 09:01 PM.
07-23-2007, 10:55 PM
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18k to build a pair of 454/500HP engines? No way. Convert to HYD Roller cams, good intakes, holley carbs, and some good aluminum manifolds for the exhaust. Stock 365HP bottom ends will be fine for 500HP. Just a basic rebuild on the bottom end will be good. Add a stroker kit for 550HP. I would think doing lots of the work yourself, you should be able to do it around 10k
07-24-2007, 08:05 AM
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What about the heads? These are the peanut heads. The 18k price I put together was from a Teague write up. That did include new JE pistons. And I had Hardin tube headers in there for around $3,500. I was also thinking about just a refresh and adding prochargers. I've been watching ebay and can pick up a couple for 5k. A stroker kit is a different crank and rods to change the stroke of the engine to increase overall cubic inch without going to a bigger bore. What do you think about the prochargers. Would the heads be alright with this setup?
07-25-2007, 11:05 PM
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If you have the original 365HP magnum heads, they are not peanut port. They are the Gm big Rectangular port heads. They will be fine and make good power. Hardin headers are nice, but not necessary with a 500HP 454. I would go with revolution marine manifolds. Great manifolds, can get two sets for 2g brand new.
Id go with bigger cams, roller rockers, edelbrock rpm air gap intakes, holley 750 or 800 carbs, which should easily get you 450HP cheap. You will notice a nice speed increase with 450 a side, in your boat I would say maybe 73-75mph with that HP. The 365HP engines respond well to cam, intake, and exhaust upgrades.
Id go with bigger cams, roller rockers, edelbrock rpm air gap intakes, holley 750 or 800 carbs, which should easily get you 450HP cheap. You will notice a nice speed increase with 450 a side, in your boat I would say maybe 73-75mph with that HP. The 365HP engines respond well to cam, intake, and exhaust upgrades.
