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Havasuhog
03-18-2004, 07:24 PM
Alpha Gear Ratio Help
I have a 92 Ultra 350 mag/alpha Gen 2 - 1.5 ratio with a High Five 21p SS prop. I bought a brand new alpha Gen2 - but it has a 1.81
ratio. The question I have is
a) Should I re-gear it to a 1.5 (Is the 1.5 stronger)
b) If I stayed with the 1.81 - Could I just just change to a 23p High Five with about the same results (MPH and WOT RPM)
c) I'm confused - I think I need another beer!
Please Help
Thanks

Dr. Eagle
03-18-2004, 08:31 PM
I don't think you need to change the ratio. I would be pretty certain of the pitch prop you need before paying the big bucks though.
Here is a little tool that should help...
Boat Prop Analyzer (http://www.boatramp.com/prop_applet/PropAnalyzerAppletG.html)
I have the same boat with a 94 350 magnum and 1.5 gears. I use a 21 pitch high 5 prop.
Using the analyzer looks like you'd need more like a 25" pitch to make all things equal.

Havasuhog
03-19-2004, 11:48 AM
Thanks Doc
I found another prop calculator from BAM marine in florida
Here's the link
http://www.go-fast.com/bam_marine_knowledge_base.htm
Im thinkin my motor would'nt have enough torque to spin a 25" pitch and still maintain MPH even though the 1.81 Ratio and 25 pitch match the table for WOT RPM. What I don't see in the calculations is the effects of low end torgue that would be needed
to turn the prop. (Im probably wrong!)
The 1.5 gears are fairly cheap. I'll call SKIPS prop shop out at Havaszoo and see what his opinon is.
Next Boat - Conquest with a Viper V-10 motor and a Saro drive.
It's easily to Dream

Dr. Eagle
03-19-2004, 12:32 PM
I am far from an expert, believe me!
But I do have the same boat and same engine as you, at least I don't think there were any great differences between the 92 and 94 Merc.
Mine runs at about 56 MPH at 4600 RPM. According to the prop calculator (which I have found fairly accurate by the way) at about 10% prop slip (which is pretty good) with 1.81 gears a 25 pitch prop puts you right around 55 MPH.
Maybe the best thing would be to put the lower gear ratio in the boat, but far as I know, it is like tires and rear end ratios. Larger tires, you need lower gear ratios. It seems like you'd be fine with a 25" prop and not have to tear down the drive, but like I say... I am no expert