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joseph m. hahnl
03-23-2005, 07:37 PM
what is the ratio of magnum 350 alpha drive .when looking for a new drive is a higher ratio number more turn on the prop per rev of the motor.

Pismo
03-23-2005, 08:03 PM
All the merc v8s are 1.5 ratio. With a lower 1.32 ratio drive you would need a lower pitch prop for it will turn faster. Dont go higher than 1.5, the V8 will twist it apart.

Rootsy
03-23-2005, 08:43 PM
Joseph,

"generally" a 350 mag will come equipped with a 1.47:1 alpha Gen II (1.5:1 alpha Gen I) drive tagging along behind it... high altitude variations or options at order, etc can dictate that the drive may be a 1.62:1 or 1.65:1 (again Gen II vs Gen I alpha). High perf applications may be equipped with a 1.32:1 ratio drive (alpha SS was available this way... 1.32 or 1.5:1)

when looking at the gear ratio it is gonna be Revolutions of the engine to revolutions of the propshaft.... same nomenclature as in the rearend or transmission of a car...

Jamie

MOP
03-23-2005, 09:23 PM
One thing I learned early on was the effect of gear ratio and prop behavior, when I was about 22 I inherited a 16 foot basket case plywood SK hull with the V drive and running gear no engine or helm. Fixing up the hull was a bunch of work but getting it to run decent was interesting, I punched a 283 out to 301 ran a Giovanni cam, camel back heads, dual quads and individual 30" dry stacks. I went nuts trying to get it wheeled, the highest pitched prop I could find made the boat very nasty and let it turn near 7K. Every time it got light it would try to walk the azz around at high speed, well here enters my non knowledge. Part of my re-hab was stripping the V drive cleaning and putting bearings in it, sounds simple enough. Well it was the type you could change ratios by draining pulling the front plate and swapping gears, well when I put it back together I figured it should have reduction. Well when I finally found the error of my ways I changed it to over drive dropped 8" of pitch, no change in launch and only a tiny change of top end but it handled like it was on rails. The prop no longer took control of the azz end when it got light. I know if my experiment on the 22 with the BH does not work out I will hunt down a 1.36 Bravo instead of a BIII. I know the prop needs to turn close or faster then the engine for good high speed handling especial in a single app. Don't ask how fast that thing was, it was fast enough and low enough to scare the crap out of me and my buddies no GPS in 62 plus anything over an 8" chop beat you to death!.

Phil

boxy
03-23-2005, 09:40 PM
One thing I learned early on was the effect of gear ratio and prop behavior, when I was about 22 I inherited a 16 foot basket case ...Phil

Was that a side paddler, or a steamboat .......... :D

joseph m. hahnl
03-24-2005, 03:30 PM
Joseph,

"generally" a 350 mag will come equipped with a 1.47:1 alpha Gen II (1.5:1 alpha Gen I) drive tagging along behind it... high altitude variations or options at order, etc can dictate that the drive may be a 1.62:1 or 1.65:1 (again Gen II vs Gen I alpha). High perf applications may be equipped with a 1.32:1 ratio drive (alpha SS was available this way... 1.32 or 1.5:1)

when looking at the gear ratio it is gonna be Revolutions of the engine to revolutions of the propshaft.... same nomenclature as in the rearend or transmission of a car...

Jamie


thanks: if i'm understanding you right it's 1 and 1/2 turns of the crank. to one full turn of the prop. which would make a 1.32 > 1 and 5/16 turn of the crank
to one full turn of the prop. lower number less crank movement more prop turn.

mattyboy
03-24-2005, 03:39 PM
Was that a side paddler, or a steamboat .......... :D

or one of those viking ships with all the oars and the capt with the horny hat :tongue: :rlol: ;) ;)

Fish boy
03-24-2005, 04:01 PM
never could understand you folks with your engine inside the boat, but I did come across a new with warranty alpha gen II for just under 2k. No idea whether this is a good deal or if anyone wants one, but since I saw the post I thought I would throw it out there. Lemme know and I will post the owners contact info and email if anyone is interested.

fish