Different Ratio Lower End Question

Pachanga2018

Pachanga2018

New Member
Feb 7, 2019
29
Boat Info
1988 Pachanga22 7.4
Engines
454 Mercruiser w/Alpha Drive
Hello All,,I have a 1:50 ration Alpha 1 Gen 1 outdrive on my boat.I bought this spare outdrive from a guy that had about 30hrs. on it and then blew his motor.He is beefing up his Hp. so he is going with a Bravo Drive.

Now for the question: The drive a bought is a Model 260 w/ 1:32 ration,,it is the upper and lower..But he included a Alpha 1 Gen 1 that has a good lower end..he says that the Alpha also was 1:32 ration,,Can I put the Alpha 1 lower unit with 1:32 ration on my Alpha upper with 1:50 ration??? He says there will be No issues.But I think it will change my RPM's or something.

Comments will be Great on this,Thanks!!!! Mark
 
it will probably work OK but you will likely have to change props so the engine will be in the recommended rpm range at WOT.....

cliff
 
The gear ratio is determined by the gear set in the upper unit - all Alpha lowers are the same. The different gear ration drives are basically matched to the engine RPM for a 4/6/8 cyl engine.
 
BillK2632 said:
The gear ratio is determined by the gear set in the upper unit - all Alpha lowers are the same. The different gear ration drives are basically matched to the engine RPM for a 4/6/8 cyl engine.
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thanks Bill.....then the OP should be OK using the prop he has as long as he uses the original upper along with the 'new' lower....

cliff
 
That's what I have always heard and I understand it - if you go to a site like Sterndrive Engineering, you seem the uppers with different ratios, but there is only one lower listed.
 
BillK2632 said:
That's what I have always heard and I understand it - if you go to a site like Sterndrive Engineering, you seem the uppers with different ratios, but there is only one lower listed.
Click to expand...

makes sense to me....:confused:.....

cliff
 
Thanks guys,,,I saw the same info on Sterndrive site...and was really wondering if the ratio was determined by both upper and lower ,or just upper..That helps me out to understand this stuff..First sterndrive owner here!!!

Side question:: I am running a High-Five 21 pitch now,,if I have this right,,I will probably have to go to a 23pitch if or when I have to put the 1:32 drive on it??
 
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if you put the 1:32 drive on your best bet is to work with a good prop shop to determine the correct prop you'll need....

cliff
 
Yea 100% the Gear Ratio is in the Upper I swapped many of lowers in my Alph days.... Same thing with a Bravo all the lowers are inter changeable... Including the bravo 2 to the bravo 3.... Witch makes the boat a beast.... Just use your old prop from your old lower....
 
I got a Great deal on a NOS 23pitch High-Five prop,,so I will be able to see what the change does to my R's if I need to adjust,,Thanks Again for the info!!!
 
Pachanga2018 said:
I got a Great deal on a NOS 23pitch High-Five prop,,so I will be able to see what the change does to my R's if I need to adjust,,Thanks Again for the info!!!
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What were u running.... Pitch, Diameter, RPMs?? And what are u switching too? Pitch and Diameter? Also what motor? How old? Hp?
 
It has a 13 1/2" 21 Pitch HighFive on it now,,I run 4600 WOT.It jumps out of the hole great.

I am not putting the 1:32 drive in at this time,,just trying to get info so I am somewhat ready if I need it.

The 1:50 Alpha in it now ,only has about 50 hrs. on it, I just bought the boat last fall and have read many horror stories of the Alpha 1 Gen 1 mated to a 7.4L Guess that's why SeaRay only did it for two years (88 and 89) then put Bravos in them.

Prior owner put a New Jasper long block (330 HP ) in it at the same time.
 
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Pachanga2018 said:
It has a 13 1/2" 21 Pitch HighFive on it now,,I run 4600 WOT.It jumps out of the hole great.

I am not putting the 1:32 drive in at this time,,just trying to get info so I am somewhat ready if I need it.

The 1:50 Alpha in it now ,only has about 50 hrs. on it, I just bought the boat last fall and have read many horror stories of the Alpha 1 Gen 1 mated to a 7.4L Guess that's why SeaRay only did it for two years (88 and 89) then put Bravos in them.
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if you avoid 'hole shots' and apply the power of the 7.4 gradually the Alpha will likely hold up just fine....

cliff
 
If it doesnt work, you can try another ratio the next time you blow up your Alpha.
My point being that a 454 connected to an Alpha is not a reliable set up. I know Mercruiser sold a lot of those combos in the 80s, but the Apha drive can't take the torque. If your Pachanga is in great shape (stringers and transom etc) and you want to keep it for a while, its much better suited to a Bravo I or III. If you stick to the Alpha, baby it on the acceleration to maximize its life.
 
At least Sterndrive Engineering Alphas are only 695.00 but they will Not warranty them behind the 7.4 or over 300 HP
 
That's what I have been trying to figure out on the pitch change..I read to much info and start confusing myself!!!
 
i think i remember reading about a 'beefed-up' or heavy duty version of the Alpha drive that handles significantly more hp....it may be worth a google search....

cliff
 
I have made Google so much money lately with all my searches.Lots of Great info out there and due to the all the ice on the lakes,i have been searching sites a lot,,LOL
 
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