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ralphcrocker
02-18-2013, 03:26 PM
What are rough speed estimates out of a classic 18 with Alpha drive

325 HP?
375 HP?
425 HP?

I understand there are many many variables just trying to get a rough consensus. These would all be 383 SBC Thanks

craigdskilling
02-18-2013, 05:47 PM
I had a very healthy 383 last year with 380hp all the best on it.but not a alpha on the back but a blackhawk and was running 78gps.i had a alpha on it but with the hp i changed it out,i coukd have kept the alph and took it easy,just didn't want to take the chance. But ithink with the lighter weight of the alpha with that kind of hp would see some good numbers and the right props.start with a25p and up from there.hope this helps

roadtrip se
02-18-2013, 11:19 PM
What are rough speed estimates out of a classic 18 with Alpha drive

325 HP?
375 HP?
425 HP?

I understand there are many many variables just trying to get a rough consensus. These would all be 383 SBC Thanks


350 Magnum, 300HP, with an Alpha will run 68-70. I have seen this all day long at the rallys.

377 Scorpion, 350HP, with a Bravo ran 75-77. This was my wife's boat for a couple of years. I do think the Scorp was underrated
by Mercury racing though.

383 X-18, not sure of the juice but I think close to 400HP, with a TRS, ran 76 GPS with my butt in it as a passenger.

All different boats and drive systems, but I hope the data helps, Ralph.

osur866
02-19-2013, 06:43 AM
Ditto to the above post by Trip, I'll add that if you intend on staying in the 400ish range and below the Alpha will be a lil faster compared to a Bravo, however the Bravo allows for adding a -2" lower and the peace of mind that the Alpha won't let go, of course there is the argument that one can buy a SEI Alpha and have a replacement swapped out at will, but the downtime and being towed in is never a great outing. If it was me and I planned on staying below 400 HP and not trying to squeeze everything out of it the Alpha would do it, I on the other hand am glad I've got the Bravo -2" hanging off my transom.
My 18 came to me with the Merc 6.2 and Bravo and totally stock would run 68-69 all day long, in ideal conditions 70-71 lite on fuel. With a few small tweaks and a few more ponies the 18 really wakes up, better question is exactly how fast you wanna go? Tell us that and I'm sure some on here will guide you in that direction in a safe smarter way. Anything above 70 you should seriously consider hyd steering for stability and safety. Good luck with you project.

osur866
02-19-2013, 07:52 AM
How fast is it that you wanna go would be the question, I'd think an Alpha boat would be faster than a Bravo boat if you intend staying in the HP you are talking about and the Alpha should live if driven with respect, add steering if you planning on running up into the 70's for added stability and safety. If you have any plans on going with more HP than what you've stated then a Bravo and -2 lower will help wake it up and improve on handeling 5 fold and let you fly the boat without fear of having the drive let go.

ralphvc
02-19-2013, 08:20 AM
How fast is it that you wanna go would be the question, I'd think an Alpha boat would be faster than a Bravo boat if you intend staying in the HP you are talking about and the Alpha should live if driven with respect, add steering if you planning on running up into the 70's for added stability and safety. If you have any plans on going with more HP than what you've stated then a Bravo and -2 lower will help wake it up and improve on handeling 5 fold and let you fly the boat without fear of having the drive let go.


I have a restored 87 minx with alpha and a pair of mild 383's (less than 100 hours) Looking for 65 in the minx. Est 320 HP. Putting the other in a classic 18 looking for 70 but considering heads intake carb probably up to 350 hp but again dont need more than 70.

gcarter
02-19-2013, 08:41 AM
My '86 Minx w/a 350 Vortec and an Alpha would run 65 on a good (cool) day.
On a more normal summer day, it'd do about 63.
I was of the impression it produced about 325 HP.

Just Say N20
02-19-2013, 10:37 AM
Ralph, Ralph, Ralph. . . . . . .:rolleyes: