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Old 05-24-2017, 02:36 PM   #1
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Default Engine done! need to replace

I have a 2001 2400 scr. Well while changing manifold and riser and did a compression test and found 4 bad cylinders and need to replace the engine. I have a 5.0 merc and looking to repower. It had an Alpha with 1.6 ratio. What's the highest horsepower power I can do? I know the Alphas have a max of 300 but have heard they can handle a little more. My goal is to get up on a plane with 4-5 people on board. Will 5.7 vortec rated at 300-330hp be good? Any recommendations? Thx
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Old 05-24-2017, 04:12 PM   #2
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I was there this time last year but mine was a non-Vortec 5.7 with a Bravo 2 and I upgraded to a Vortec 5.7.

Are you certain you need a new engine and just not a valve job or are you looking for the power?

IMO the Alpha can handle the Vortec if stock.
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Old 05-25-2017, 12:32 AM   #3
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the alpha will handle the 5.7... I did a repower with my other boat(1998 trophy 2352 about the same weight as yours)... went from a 1998 305 to a 2014 350 MAG MPI(320 HP)... just remember you do not have a drag boat so don't hammer the gas all the time and you will be fine... and BTW it changed the boat completely I'm SOOOOO happy I did it!
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Old 05-25-2017, 03:34 PM   #4
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Alpha's have a max HP rating of 300HP. Yes, you can go higher, but make sure you're not hammering it and keep the handle on the throttle, getting ready to chop [in case] the second the prop comes out of the water. (ala offshore racer style).
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Old 05-26-2017, 12:52 PM   #5
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Thanks for the info. I could spend the money and get the engine repaired but with the cost of cylinder heads and the labor it's just easier to replace and squeak out a little more ponies.
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Old 05-26-2017, 12:59 PM   #6
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Wish I could do it myself like you but don't have the know how or the space. I "google" fix things all the time but this would be too big and would take me the entire summer lol
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Old 06-06-2017, 10:22 PM   #7
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Ok another follow up question. Since the boat originally came with Alpha 1 gen2 @ 1.62 ratio and the 5.7vortecs usually use 1.47 ratio, what should I do to compensate if anything?
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Old 06-07-2017, 01:12 AM   #8
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IMO initially nothing, see how it performs first. Next would be a change in pitch to try and offset the ratio difference. Finally sell you drive to buy the correct ratio one.
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Old 06-07-2017, 10:38 PM   #9
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Try the mercruiser calculator. Compare pitch differences between old engine and new using the ratio you have.
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