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View Full Version : Are all Alpha One Outdrives the same?



yembo77
09-23-2013, 11:09 AM
Despite the generational, rotational, and ratio differences, are all Alpha One the same as far as load bearing capacity? I have a Gen 2 Alpha One on my 87' ZB21 with a 5.7 V8, but also a gen 2 Alpha One on a 95' Cuddy with a 3.0 I4. Do you think those drives would be interchangable?

Thanks,
Matt

gcarter
09-23-2013, 11:17 AM
Yes, they will bolt up.

MOP
09-23-2013, 12:00 PM
What you will more than likely run into the ratios will be different, on lighter boats 1.5 is the norm but on heaver boats the ratios jump up. You can make up for this with different props, 1.5 use lesser pitch then the higher ratios.

yembo77
09-23-2013, 01:54 PM
Ah ok. So the internals of the Alpha can handle the power of a standard 350 merc? There's no V8 specific output shaft or different splines?

Cool! Glad to hear it. That means I have a spare outdrive. Also good to hear that if it is a different ratio, I can fix that with a prop.

Thanks!,
Matt

MOP
09-23-2013, 02:37 PM
The decal on the side of the upper housing gives both the serial number and ratio, ou can get a good idea of the pitch ou ma or ma not need during a swap.

Phil

joseph m. hahnl
09-23-2013, 05:40 PM
Ah ok. So the internals of the Alpha can handle the power of a standard 350 merc? There's no V8 specific output shaft or different splines?

Cool! Glad to hear it. That means I have a spare outdrive. Also good to hear that if it is a different ratio, I can fix that with a prop.

Thanks!,
Matt Yes they are V8 specific. 1:5 for small blocks. Gen 1's used a 1:32 for big blocks. the 1:6 is for V6's and 4's. the closer the ratio the stronger the gear set.

a high torque motor with a 1:6 Upper, pitched up to compensate for loss of rotation, Is more apt to shear the gearset:bonk:

mattyboy
09-23-2013, 07:40 PM
Matt
here is a chart the drive on the 95 4 banger is most likely a 1.9

http://www.seilermarine.com/info/mercruiser-drive-ratio-chart.php

the rule of thumb for every inch of pitch you go up is a drop in rpm of 200 and jumping gearsets is about the same a drop in ratio is a drop of 200 rpm with the same prop.

as an example if you are at 4800 rpm with a 1.5 and a 23 pitch prop just a gear change to a 1.6 would mean 5000 rpm then a 1.8 would be 5200 rpm a 2.0 would be 5400 rpm so to stay at 4800 rpm would would need a 26 ish pitch prop

BUIZILLA
09-23-2013, 08:20 PM
my experience has shown that if you go from a 1.5 to a 1.65 drive, thats a 10% increase, consequently your rpm would rise exponentially the same, 10%

with that said, if you had a 20" prop with a 1.5 you'd need a 22" prop with the 1.65

mattyboy
09-24-2013, 11:14 AM
Matt

let me know if you are going to get out on the lake, looks like this weekend is going to be in the mid 70s a few more of these cold nights and the trees should get the message to start their colors should be beautiful scenery.

biggiefl
09-24-2013, 02:07 PM
Gears are only in the upper, lowers are identical. If putting a 130hp on a V8 I would definitely change the gears to a 1.5. a huge prop on a 1.9 would make for some lousy performance and possible holeshot. The 87 should be a Gen 1 unless relpaced. my 87 Baja and 86 Scarab both had gen 1's.

joseph m. hahnl
09-24-2013, 05:39 PM
STOP! Back up:propeller: (Gen II} came out in 1991 an 1987, as was pointed out would be (Gen I)The answer would be "NO" :bonk:! They are not interchangeable An Alpha one (gen I) will not fit:smash: in any way on a Alpha one (Gen II). Every bolt pattern is different in the upper and lower, .:doh:


http://ts4.mm.bing.net/th?id=H.4950002482613991&w=250&h=153&c=7&rs=1&pid=1.7

http://i302.photobucket.com/albums/nn102/clninja/badpshopoftasillightsreverse.jpg

Planetwarmer
09-28-2013, 12:12 PM
STOP! Back up:propeller: (Gen II} came out in 1991 an 1987, as was pointed out would be (Gen I)The answer would be "NO" :bonk:! They are not interchangeable An Alpha one (gen I) will not fit:smash: in any way on a Alpha one (Gen II). Every bolt pattern is different in the upper and lower, .:doh:


http://ts4.mm.bing.net/th?id=H.4950002482613991&w=250&h=153&c=7&rs=1&pid=1.7




Party pooper!
:party::frown: