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I gained 6mph @ around 500-600rpms with the addition of Alpha SS on my Challenger. From 75GPS to 80.5,
21' Challenger 7.7' beam 2600lbs wet stock with all Merc cast iron, so my aluminum setup is alot lighter. 22* deadrise pad bottom non step 385ci SBC approx 475hp Before propshaft depth 5" After 2.5" SS shorty = 3.5" I did not like the shorty the first weekend of testing. Hell I could barely get on plane the first time I tried due to prop blowout with a 3 blade cleaver. I was running a Merc Racing 23p 14 5/8" Hydromotive race labbed cleaver. I had insane prop slip at anything below 50mph. I'm talking at 3,000rpms I'm barely running 22-24mph... Could hardly plane off and turning was non existent without blowing out the prop. At WOT it ran damn hard though with a decent slip number of around 9%. I knew there was somehting to be had with the right prop so I worked with Todd @ Hydro. He said there was just not enough blade in the water with the 3 blade cleaver design. We went with a 22p QIV 4 blade cut down to 14 3/4" heat treated and lab finished. Turned out to be the perfect prop for the drive height and this boat. Corrected all planing, turning issues and was 2.5mph faster up top. When changing something as drastic as the propshaft depth, you must do alot of prop testing to dial in the setup. You are essentially back to square one and must start all over to see what the hull likes. The whole shorty idea is less drag more speed. Works almost every time on any boat, just needs dialed in and that usually involves alot of time testing and money for either buying or borrowing props. Usually more work than the average individual will go through. SS drives in good condition are rare and usally in excess of $1500. Most parts are interchangeable with an Alpha 1 as far as gears, bearings, seals. The vertical driveshaft as mentioned before is NLA by Merc and if broken you are done with this drive. Or, if you break gears and bust the case. |
I don't have a direct speed comparison because I ran a stern jack with the ss which solved the x dimension issue on my boat.
86 Scarab I, 21 ft, 454 (330hp), alpha I (1.50) As above with 21p mirage 62 mph Added stern jack 23p mirage 66 mph Alpha ss (1.32) and stern jack 21p mirage 71 mph The stern jack adds 8" of setback and unlike an extension box increases the vertical range the drive moves when trimmed. Result is good planing and top end. Don't know if they still make a stern jack but paid about $1500 at the time. After it is all said and done I gained about 9mph with no increase in hp which is pretty amazing. Down side is I spent about as much as it would have cost to switch to a bravo. Of course the bravo is a bigger heavier drive which would result in lost speed for the same hp. Again, I still have the alpha ss drive in running condition and will sell it for exactly what I paid for it $3k. |
Looking to buy a alpha ss
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Originally Posted by 220sport
(Post 4581754)
Looking to buy a alpha ss
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Alpha SS
Originally Posted by Biggus
(Post 3644316)
Performance gains all depend on prop shaft height. How many inches below the hull bottom to the center of your prop shaft with the std Alpha?
If the X-Dimention is agressive, you might not gain much, if anything by going to an Alpha SS. (If I remember correctly the SS is 2.75" shorter from input to propshaft) I've got an '86 22 Pachanga, installed an Alpha SS and lost speed as the prop shaft was way too high with the SS, The X on my boat was cut very high from the factory. |
longest of longshots... might you still have the ss?
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looking for alpha one ss lower unit...
Originally Posted by papps
(Post 3646180)
I don't have a direct speed comparison because I ran a stern jack with the ss which solved the x dimension issue on my boat.
86 Scarab I, 21 ft, 454 (330hp), alpha I (1.50) As above with 21p mirage 62 mph Added stern jack 23p mirage 66 mph Alpha ss (1.32) and stern jack 21p mirage 71 mph The stern jack adds 8" of setback and unlike an extension box increases the vertical range the drive moves when trimmed. Result is good planing and top end. Don't know if they still make a stern jack but paid about $1500 at the time. After it is all said and done I gained about 9mph with no increase in hp which is pretty amazing. Down side is I spent about as much as it would have cost to switch to a bravo. Of course the bravo is a bigger heavier drive which would result in lost speed for the same hp. Again, I still have the alpha ss drive in running condition and will sell it for exactly what I paid for it $3k. might you still have the ss drive? |
Originally Posted by 1988pachanga22
(Post 4761130)
might you still have the ss drive?
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Originally Posted by Strokin
(Post 4761146)
I still have my SS Drive but it's on my boat..
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https://cimg4.ibsrv.net/gimg/www.off...877d39e63.jpeg
just fully rebuilt new hd 1.32 gears, a lot of new and updated parts. Blueprinted case. Awlcraft paint. Less then 2hrs of test time on the hose and at the dock Pm me if interested.. 3k obo |
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