1989 mercruiser 454 mag on alpha drive.

chris0061

Chief Petty Officer
Joined
Jun 17, 2007
Messages
446
I picked up a 21 foot regal br 1989 with the 454 mag in it. The outdrive is a alpha one. I looked at my book and it said that year with that engine had 1.32 gears in the outdrive. The outdrive is blown in the lower unit, not sure if there is damage in the upper. My question is would it be ok to put a alpha drive with a 1.50 ratio on it for now till I save up for a bravo conversion. I have a older Mr ready to instal... thanks in advance...
 

alldodge

Moderator
Staff member
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Mar 8, 2009
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40,582
I picked up a 21 foot regal br 1989 with the 454 mag in it. The outdrive is a alpha one. I looked at my book and it said that year with that engine had 1.32 gears in the outdrive. The outdrive is blown in the lower unit, not sure if there is damage in the upper. My question is would it be ok to put a alpha drive with a 1.50 ratio on it for now till I save up for a bravo conversion. I have a older Mr ready to instal... thanks in advance...

No problem-O, going to need to change the prop. Now if you don't hammer the throttle, the drive may last as long as you have the boat
 

NHGuy

Captain
Joined
May 21, 2009
Messages
3,631
Yup, I did a build up on my small block and left it Alpha. I put in Amsoil Severe Gear as an added help. But I never, I mean never hammer the gas. Your big block has bunches of torque, so just roll on the power easy. The place to really finesse it is just as the boat is climbing onto plane. Just ease it past the bow wave.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Need to make the prop 13% bigger. If you are running a 17" (with the 1.32 drive), then you'd need a 19" with a 1.5 drive....

Chris......
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,286
Surely it would be a smaller (not bigger) prop that is required ?
If you were using a 19", would need to go to 17"...as an example.
Unless I'm having blunder to myself here ? It is Monday, after all !
 

QBhoy

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Mar 10, 2016
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8,286
Doh.
Of course...you said you are going from 1.32 to 1.5. I was having a blunder. Realised just as soon as I hit the send button ! What a wally.
Bigger prop required ! Ignore me....
 
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