On vacation few weeks ago I broke the vertical driveshaft in my alpha 1. It broke about the top inch off the splines and not in the groove. My ? I guess is why it broke there? I bought a clever prop for it and changed the upper cap that goes on top the upper part of the drive. I gained a few mpg with the prop and was running it harder than normal. I got more power than I should with the alpha. I'm wandering if the prop broke it or maybe the cap on the upper was not adjusted right??

you said you have more power,maybe the extra power killed the shaft.what do you estimate your hp to be?

375 or so. Same boat with a 330 hp big block will run about 3 mph less than I get. I know there is more to it then that.

What boat ? Approx weight ?
What gear ratio ? What pitch ?
What cid is motor ?

Baja 1988 235 force. I have no idea on weight. 1.50 gear 15" by 19 pitch prop. Had a 14 1/4 by 20 on it before. I was just cruising along about 3200 rpm and it went to 5000 and the boat stopped. I also got some air on some big waves the day before but I did not have it wide open when I come back to the water! !

What cid ?

How old is the drive ?

really makes no diff what broke it. shaft is done. quickest fix is another drive from craigslist. 235 Baja is heavy for a 23 foot boat. 375 is a lot of power for an alpha. real question might be..."why did it hold up so long?"

355 Ci and it's the original shaft from 1988. I do baby it alot trying to not brake anything. I'm hoping to swap to bravo this winter so I can upgrade my engine. I plan to buy a new shaft and just repair it. Friend was trying to tell me my new prop broke it but I was thinking not!