alpha one gen two input speed question likely for Al

212rowboat

Al, I hate to bug you, man.. and maybe there is someone else who can also answer- but... 

is it the torque or the speed which wipes the alpha drives?  I realize excessive TQ will kill it, but will moderate TQ and pushing to 5500RPM do it just as easily?  

This is of value to me because i'm determining the engine speed  and powerband placement of my build- and I'd rather turn higher RPM's and use lower pitched prop... i'm aiming for 5200rpm... too much? the engine will handle it... no worries there.. my concern is about the drive.

Michael T

Here's what I experienced:

In my Rinker 190 I swapped my 4.3LX for a 350 magnum 300HP keeping my Alpha drive. My limiter was set for 5K. I did notice deposits on the drive after a few high speed runs.

So, I cleaned the drive tower and immediately changed the gear lube. It was okay and not discolored. I then immediately  purchased an SS drive showed that flooded the top of the drive tower. No more deposits.

IMO, if you have a drive shower and you keep an eye on your lube and run premium synthetic gear lube you should be fine.

If anything I would worry about twisting the drive than running it at 5200 +/- RPM...... BUT I doubt very much you will twist that drive with a 5.7 even if you do breathe on it a bit. Even if you did manage to get 300HP out of it (which I think unlikely given the mods you are going to do ) IMO you'd still be fine.

And you have said you aren't swapping the engine to go wave jumping and racing so, again, I don't think you'll twist that drive.

I built that 350 mag to have pure fun and race anybody around. I treated it far harsher than I think you ever will and that Alpha was fine.

I had never before or after run a boat so hard. I changed the engine oil very frequently and the drive lube too. I raced it around often for 15 minutes at WOT - for years and despite all of that I never hurt that drive.

Of course when I stroked that 350 Magnum to a 390HP 383 I had to go bravo l or THAT would have twisted the drive!

F1100

Gears usually fail from "lash" or abrupt power changes.

Oiling/lube type is a low failure mechanism on gear sets when power becomes an issue and is not a real factor.

On race cars I can say that most gear failures are from abrupt changes in torque. AKA mashing in the throttle..or on decell.

Gear sets that are ramped up in power application can take vastly more torque than they were intended for.

In fact I bet if you had some sort of throttle ramp up servo, you could put thru 3x+ more torque than the gear set was rated for perhaps more before the gears actually sheared.

Case in point..some of the high power turbo cars we built, that had a stock 140hp, gear set/tranny/diff/ drive shafts.. were able to take 550hp+ ..however would fail quick if power inputs were not smooth, like dumping the clutch ect..

212rowboat

those gears are tiny compared to automotive ring and pinion, and you gotta figure they're reduced once and turn a 90* once using the gears alone- that's hoping the gimble bearing and the universal do their job the way they're supposed to... the question of cut or cast comes to play... there is a tremendous amount of force on both sets of those gears... 

the new drive demands a break in period of ten hours and a lube change then and again at 20 hours... if the drive survives the first 20 hours, chances are it's going to be good to go... 

MT, I doubt I'll break 300 ponies... that isn't my aim, anyway, BUT, the torque will be greater than your average mercrusier 5.7 Mag, and it will be found lower in the curve. 

I'm playing with the idea of advancing or retarding cam timing right now.  What i do will determine what kind of power that drive will have to work with.  If I retard the cam timing, I'm looking for higher RPM's and overall engine speed but not necessarily the torque that comes with it- if I advance, I'll be hitting the torque much earlier- around 3k to 4.5k RPM's, but the engine is likely to top out (curve) around 4.8~4.9RPM (which is fine, and dead in the range merc rec's for their engines and their drives)... if I retard the cam timing I should spread the curve over a higher range- likely not kicking hard until 3.5-3.8k RPM, but still holding upwards of 5.5kRPMs... 

all of this is likely to be determined by that drive and if the speed will kill it or if the torque will... I bought a 'no questions asked' warranty on the drive set, which is solid according to users who've used it- so I've got margin for error a lot of folks don't... 

Black_Diamond

Most gears fail from metal fatigue. Pitting/spalling that progresses to tooth failure. Reverse loading adds to the problem, especially if done hard. Assuming good bearings and proper lash set it almost always boils down to lubrication failure. 

Black_Diamond

Sweet!