alpha 1 Gen 2 sterndrive broken lower drive shaft

akdad

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Scratching my head on this on! I have had 2 broken lower drive shafts break on 2 different outdrives. Last one was a complete new Mercruiser outdrive 2017 1.47 ratio with mercury 15p AL prop and Mercruiser 5.7L 250hp. Did not hit anything, same prop on both, looks like new. Anyone else run across this problem? Is my luck that bad? Long slow trip back to harbor on kicker x2 ...NO fun! Shaft#45-853648IMG_4174 (2).JPG
 

dubs283

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Could be bad luck, but not likely

What is your idle speed? Is shift cable and throttle cable adjusted properly?
 

Scott06

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What boat ?
Under his photo -

1998 2452 Bayliner Cierra Express 5.7L alpha 1 gen 2

I think we are thinking the same thing- 24 ft is pretty big for a single Alpha drive ?

wondering given the OPs photo if lots of trolling is involved?
 

akdad

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Could be bad luck, but not likely

What is your idle speed? Is shift cable and throttle cable adjusted properly?
Idle speed at factory spec, shift cable all good . This happened after getting at cruise speed 26-28 MPH
 

Bondo

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Idle speed at factory spec, shift cable all good . This happened after getting at cruise speed 26-28 MPH
Ayuh,..... Welcome Aboard,..... I've never seen one break there,.....
Older Alphas would snap the shaft up high, at the o-ring groove,.....
 

akdad

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What boat ?
1998 2452 Bayliner cierra express originally had mercruiser 5.0L 225hp alpha 1 gen 2. Upgraded in 2012 to 5.7L with same outdrive. 2017 we had been cruising about 28 mph @ 3600 rpm approx. when first lower shaft broke. Replaced with new complete mercruiser alpha 1 gen 2 with 1.47 ratio SN#SR53738. Alpha 1 gen 2 are rated for 300hp and was not over propped. WOT was with in spec. 2nd time happened running about same speed with newer outdrive approx 100hr on it from 2017-2019 & 2022.
 

alldodge

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Woops
The boat weights about 4800 so its kind of heavy for the ratio
Can you reach 4800 rpm at WOT?
 

Scott06

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1998 2452 Bayliner cierra express originally had mercruiser 5.0L 225hp alpha 1 gen 2. Upgraded in 2012 to 5.7L with same outdrive. 2017 we had been cruising about 28 mph @ 3600 rpm approx. when first lower shaft broke. Replaced with new complete mercruiser alpha 1 gen 2 with 1.47 ratio SN#SR53738. Alpha 1 gen 2 are rated for 300hp and was not over propped. WOT was with in spec. 2nd time happened running about same speed with newer outdrive approx 100hr on it from 2017-2019 & 2022.
My first thinking is the boat weight not necessarily power level is at the upper limit for the drive. Might be worth a call to merc tech support.

I assume none of the bearings locked up?

keeping up with lube changes?
 

akdad

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Woops
The boat weights about 4800 so its kind of heavy for the ratio
Can you reach 4800 rpm at WOT?
WOT spec was between 4400-4800 so the 15p prop was in that range. Will check old outdrive again for ratio on it.
 

akdad

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My first thinking is the boat weight not necessarily power level is at the upper limit for the drive. Might be worth a call to merc tech support.

I assume none of the bearings locked up?

keeping up with lube changes?
Thanks, will give them a call. No bearings seized, only a few chips off lower gears. Checking prices to maybe switch to a Bravo3.
 

Scott06

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Thanks, will give them a call. No bearings seized, only a few chips off lower gears. Checking prices to maybe switch to a Bravo3.
Would need transom housing as well as drive.

is your engine carbed or mpi . Would need a engine driven water pump. I assume the chipped gear is the root cause maybe locking up the driveline
 

akdad

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Would need transom housing as well as drive.

is your engine carbed or mpi . Would need a engine driven water pump. I assume the chipped gear is the root cause maybe locking up the driveline
carbed it is. Thanks, had not thought about external water pump for Bravo series.... I knew I would need to change transom mount. Any other dealings with switching to Bravo 3 ..... worth it or not? Brands Mercruiser vs SEI vs ?
 

alldodge

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SEI doesn't make a B3, Merc still has patent

Its unusual even for a heavy boat to brake in the same spot other then over loaded. Might think about changing ratio to a 1.80 or 2.00 to reduce stress
 

akdad

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SEI doesn't make a B3, Merc still has patent

Its unusual even for a heavy boat to brake in the same spot other then over loaded. Might think about changing ratio to a 1.80 or 2.00 to reduce stress
I'm confused, SEI lists a B3 complete for $4k. Taking apart old outdrive to check ratio of original drive.
 

alldodge

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Your right, last time I looked B3 wasn't there
If your Alpha was doing fine when working, might think about B1, less seals to deal with and a bit less weight then B3
 

Searay205

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a metallurgist cold tell you what caused it just by looking at the fracture geometry. Do a search in your area for a materials testing lab. Walk in front door and ask them how much for an alalysis. I imagine before they even talk price they will tell you what caused the failure for free. My dime store opinion looking at comparable failure examples indicate torsional overload. Bayliner = marginal build. That little outdrive can't sustain the pain, pushing 6klbs? loaded. **** my 16 foot Starcraft had an alpha 1 behind a 3.0 liter.......
 
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Scott06

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carbed it is. Thanks, had not thought about external water pump for Bravo series.... I knew I would need to change transom mount. Any other dealings with switching to Bravo 3 ..... worth it or not? Brands Mercruiser vs SEI vs ?
The bravos and alphas i think use a different ignition module if you have thunderbolt V , but i think you could stay with the alpha module and disconnect the unneeded shift interrupt switch.

while a B3 would likely make a better performing boat, as AD mentions if you are happy with single prop you could save a few bucks and avoid higher corrosion potential of B3 going with a bravo one drive. There are a few guys on ebay who offer fresh water tear outs if you are on a budget.
the water pump shouldnt be too bad you could use bravo parts for the pump and brackets or use a jabsco or other crank driven pump if you have room.
id be interested to hear what merc says. I dont know if changing the ratio would make any difference as the failure is in lower, although i am surprised that on an original 5.0 220 hp in a 24 ft they used a 1.47 drive. My 21 ft sea ray if equiped with same engine came with a 1.62. Ive heard of trolling wrecking couplers from back and forth but you dont troll on the drive right?
 

akdad

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Ok, took upper set apart on old unit and counted teeth 24-24 with s/n 0L119519 sterndrive which is either 1.62 or 2.0 ratio which means I was sold wrong ratio of 1.47. Must have been too stressed out....now second guessing what i remember of W.O.T. setting I had with newer outdrive and prop. I know it was dialed in with old outdrive and 5.7L w/15p prop.
 
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