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Thread: Alpha drives and the 454 Mercruiser

  1. #1
    Join Date
    Oct 2014
    Posts
    1

    Question Alpha drives and the 454 Mercruiser

    Hello all,

    New to site but wondering if there is some help out there. When Mercruiser came out with the 454 in 1987 they originally paired it with the alpha one with very poor results. I have a Baja with that pairing but it currently has a SEI06 replacement unit. Did SEI fix the issues related to the torque of the 454? Warranty only says too 300HP only? Any help would be appreciated.

  2. #2
    Join Date
    May 2006
    Location
    New Jersey
    Posts
    155

    Default

    Big blocks and Alpha drive require a gentle hand on the throttle and a light boat to stay together.Friend had the BAHA24 Ft with the same package, Use a gentle hand untill your planed up and then go for it.

  3. #3
    Join Date
    Nov 2006
    Posts
    661

    Default

    The issue is that the drive is too small to handle the torque of that big engine. That is why that package was only put together for a couple of years, then they switched to the bravo. As bt doctur said, you have to be gentle with it until you are on plane. Some guys will break them in a year, others will never have a problem, just depends how you treat it.

    Tech Support

  4. #4
    Join Date
    Jan 2016
    Location
    St Paul MN
    Posts
    0

    Default

    This seems to be such a "tot topic" for us 7.4 Alpha 1 owners. I know there are multiple posts out there but this being the newest, I figured I would post my questions here.

    I have a 23' SeaRay weekender with the dreaded combo, and I think I am going to bite the bullet and buy the 1:47 ratio and figure out the best prop. My thought is pay my local Mercruiser guy $1000 to go through my OEM Alpha, or spend a little more, buy a NEW SEI, KEEP my OEM for a back up and maybe rebuild in the future!

    My question is PROP size and blade #. I know I don't want to go too crazy on pitch as the higher the pitch, the more torque on the lower unit. I am NOT a "out of the hole" type driver and I ALWAYS roll on the power slowly! I do some WOT runs on the Mississippi here in MN, but will always cut back to about 90-95%.

    Would a 4 blade prop with a little less pitch be a little better or a three with MORE pitch? Also, what about prop SIZE? Would a 14.5 X 17 or maybe be a 14.75 X 15 4 prop be better than a 15 X 16 or 14.5 X 17 three blade?

    My thought is maybe a 4 blade prop, with a little LESS pitch may help a little? I need to buy a new prop anyway! I am thinking it SHOULD have the rubber insert as well? Anything to help baby that drive!

    Any thoughts? (Or am I WAY over thinking this....)

    Also, the MN boat show is next week....will there be any SEI reps at this show?

  5. #5
    Join Date
    Jan 2016
    Location
    St Paul MN
    Posts
    0

    Default Would prop selection help?

    This seems to be such a "tot topic" for us 7.4 Alpha 1 owners. I know there are multiple posts out there but this being the newest, I figured I would post my questions here.

    I have a 23' SeaRay weekender with the dreaded combo, and I think I am going to bite the bullet and buy the 1:47 ratio and figure out the best prop. My thought is pay my local Mercruiser guy $1000 to go through my OEM Alpha, or spend a little more, buy a NEW SEI, KEEP my OEM for a back up and maybe rebuild in the future!

    My question is PROP size and blade #. I know I don't want to go too crazy on pitch as the higher the pitch, the more torque on the lower unit. I am NOT a "out of the hole" type driver and I ALWAYS roll on the power slowly! I do some WOT runs on the Mississippi here in MN, but will always cut back to about 90-95%.

    Would a 4 blade prop with a little less pitch be a little better or a three with MORE pitch? Also, what about prop SIZE? Would a 14.5 X 17 or maybe be a 14.75 X 15 4 prop be better than a 15 X 16 or 14.5 X 17 three blade?

    My thought is maybe a 4 blade prop, with a little LESS pitch may help a little? I need to buy a new prop anyway! I am thinking it SHOULD have the rubber insert as well? Anything to help baby that drive!

    Any thoughts? (Or am I WAY over thinking this....)

    Also, the MN boat show is next week....will there be any SEI reps at this show?

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Sterndrive Engineering, Inc. (SEI) manufactures a stern drive designed to replace Mercury Marine's MerCruiserŽ Alpha OneŽ, R, MR, Gen II and Bravo OneŽ stern drives. MerCruiserŽ Alpha One, R, MR, Gen II and Bravo OneŽ are trademarks of the Brunswick Corporation. SEI has no affiliation with the Brunswick Corporation. Consequently, any warranties governing products and or sold by Brunswick Corporation will not apply to products manufactured and or sold by SEI, or to products damaged due to the operation of an SEI product.