Alpha One drive breaking upper gears

Have a 1985 Chris Craft scorpion 186, original motor was a mercruiser 305 200hp Alpha 1 Gen 1 1.65 gears, I replaced the motor with a indmar 5.7l vortec with a holley 4150 dual feed 315hp.everything was fine had a couple of outings with the boat had replaced the prop with a 23p turbo, ran good about 4500-4600 rpm wot at around 50-53 mph, decided to take a 2 day trip on the mississippi and about 50 miles into the trip after refueling we started down river and the drive clunked and then was fine but after a few miles started clicking and grinding, so shut it down and had it towed to the next town, after getting it home pulled the top cover off and found the upper input gear teeth sheared off, replaced the entire drive with another drive 1.50 gears from a 260 hp 350. so take the boat out few times went back to the 21p prop due to the gear change and following a friend down the river running wot about 4600-4700 rpm started to trim the drive up and all of a sudden heard a ratcheting sound and shut down the motor, thought I had spun the prop but that checked out, got towed in and checked the upper gears tonight and the upper input gear teeth were completely sheared off, what could be causing the gears to give out, don't hammer on it from a dead stop, don't pull skiers or tubers, pretty much just cruise around at about 25-35 with a occasional wot run. I have heard that the alpha is good for only 300 hp but I can't believe that 15 hp would cause this to happen, looking at rebuilding the drive but was wondering if anyone makes heavier duty gears. guess I'm just looking for some options.
Thanks for any input
bgiese

Re: Alpha One drive breaking upper gears

main cause of ruining upper gears is gear lube loss

did you pressure test the new drive before installing it??

Re: Alpha One drive breaking upper gears

If you truly baby it like you say, those gears (given proper lube!) shouldn't break with 600hp. It's very possible your first drive was simply ready to break, and you bought another one in the same condition. And if these drives are ever run with water in the oil or low on lube, the upper gears are the first to go.

Re: Alpha One drive breaking upper gears

Maybe you need to get a new drive instead of one that's used. I do know there are 383's out there with alphas and they make more power than you.
What about a Sterndrive Engineering alpha 1 clone? New with warranty on sale for $1200. Then get the Royalest Purplest lube you can find and stay away from wide open throttle til you are past 3000 RPM.
And if your drive does not have a remote lube reservoir put one in, that way you will always be able to see the level of lube in the drive.
If you do go for another used piece open the lid before you buy/run it. Make sure the gears are right. And as the above post said, do fresh lube and a pressure test.

Re: Alpha One drive breaking upper gears

No I did not pressure test the drive, it was sold to me as having been pressure tested and off of a running boat. the drive was still full of gear lube when I pulled the cover.
bgiese

Re: Alpha One drive breaking upper gears

Well maybe you are hitting the gas too hard. Just roll it on. don't jackrabbit the boat even though it's way fun!

Re: Alpha One drive breaking upper gears

If you still have the lube check it for water at the bottom, any root beer float going on?

Re: Alpha One drive breaking upper gears

if the gear teeth were broken, then there was either an issue with a crack in the gears or shimmed improperly

if the gear teeth look like they were smashed, then it was a loss of lube or cheap lube

buying used stuff is always a gamble, and yes you can get heavy duty gearsets

maybe both drives had been worn just enough and more hp killed em

Re: Alpha One drive breaking upper gears

have not drained the drive yet, will do that on my next day off. have been looking at the sei 106 as as possible replacement, local marina says to stay away from them, but from what I have read and the warranty makes them sound okay. if I was to have the old drive rebuilt where would one get the heavy duty gears to replace the original ones with. have checked several sources but have not found any mentioned yet.
thanks

Re: Alpha One drive breaking upper gears

The Heavy duty gear set for 1983 thru 1990 1.5:1. R,MR,Alpha 1 drives part # is 43-18411A4. You might also consider 1.32:1 Gears. My info is a few years old but its a place to start. any merc dealer should be able to find what you need.

Re: Alpha One drive breaking upper gears

"...don't hammer on it from a dead stop,..."
A prop will slip in the water, completely different situation from a fast car, where you pop the clutch and shock the whole drive train. My 5.7 makes ~330 hp, I punch it fully from a dead stop every time to get on plane fast, no issues. (Alpha gen 2)


"...if your drive does not have a remote lube reservoir put one in,..."
That's easier said than done, if the leg doesn't have provision for it. I tried it, got frustrated and gave up.