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Old 08-03-2019, 10:22 PM   #1
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Thumbs down Hit outboard leg on rock

Hi Everyone,

I'm gutted to write this but hit the leg at 70% speed today on a rock that wasnt marked on the lake. Its an Alpha One Gen2 leg on a Mercruiser 4.7 1997 LH Engine...

The engine appears to be fine however will cut out when I try to put it in gear. Haven't had a chance to take the prop off yet and there appears to be a chunk missing from the bottom of the leg (fin). With the engine off and throttle in gear the prop moves in both directions (including reverse) with a clicking sound in one direction.

Could anyone please recommend how to go about diagnosing and see what I need to do? I'm hoping its just a sheerpin and prop replacement.

Thank you in advance.
(insert crying here)
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Old 08-03-2019, 10:47 PM   #2
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The skeg and the prop are easy fixes. It's your comment "The engine appears to be fine however will cut out when I try to put it in gear" that has me concerned. If by that you mean the engine stalled when you put it in gear you could have done internal damage to the outdrive.

For the skeg : https://express.google.com/u/0/produ...RoC6bUQAvD_BwE
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Old 08-04-2019, 01:37 AM   #3
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The drive must in the lowered position then in forward try turning the prop in both directions, it should only turn one way. Now put it in reverse and it should only turn the other way. Remove the prop and start the engine and see if it shifts into forward and reverse.
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Old 08-04-2019, 02:34 AM   #4
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With engine off and in neutral, spin the prop fast and see if it wobbles. Drain the leg gear oil and check the oil and plug for metal chunks.
If it passes the tests Mike recommends, prop spins true, and the gear oil is clear, next step is to remove the drive cap and take a look at the upper gears.
I would check the engine coupler also, but that wouldn't account for the engine stalling. Also check that the shift shaft coupler is still seated properly.
I'm thinking best course now is to assume there has been gear damage and try to locate which gears.
You should have spun your prop hub during this incident, that's one of reasons for the hub.
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Old 08-04-2019, 04:11 AM   #5
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Quote:
Originally Posted by mmwjr View Post
The drive must in the lowered position then in forward try turning the prop in both directions, it should only turn one way. Now put it in reverse and it should only turn the other way. Remove the prop and start the engine and see if it shifts into forward and reverse.
Start with this....
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Old 08-05-2019, 04:45 PM   #6
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Default Took the prop off

Thanks for the solid advice everyone.

We took the prop off today and it looks as if the middle pin has a wobble. I think the skeg hit the rock first and chipped off a bit into the prop.

With the engine off, it does rotate in both directions regardless if its in forward or reverse gear. Leg has a clicking sound when turn the prop in one direction. Unfortunately we got caught in torrential rain and couldn't diagnose further..

I'm praying its just the lower leg unit/prop. The bellow and seal around the transom/upper leg appear to be intact. Going try diagnosing again at the weekend with the engine on and prop off..

Hopefully this is something I can fix myself.. May even do a youtube video for any other poor soul who encounters the same problem.

If it is just the lower leg unit do you think someone with 0 mechanic experience can replace it or should I get a pro to do it? I'm guessing its just drain the gear oil, replace the leg, pump in gear oil from the bottom? I'm up for the challenge and learning experience but always think safety first.

Will keep you all posted and thank you again for all your advice.

The guy who rescued me from the lake had a funny acronym BOAT = Budget On Another Thousand #NeverForget
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Old 08-05-2019, 05:02 PM   #7
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B.O.A.T. is commonly know as Break Out Another Thousand.

Replacing the lower unit is the same procedure as removing it to replace the impeller. Dain lube, unbolt (don't forget bolt under rear anode), remove. To install make sure lube seal is installed on outer wall the reverse the above. Note shifter has to be in reverse when removing and installing the drive.

The unit can be rebuilt but based on the damage I doubt it would same money over a new one. IMO don't get the aftermarket sterndrive engineering one to save money as many end up having them go bad although its under the three year warranty but you first have to return the bad one so you can loose a month in the exchange process.
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Old 08-06-2019, 04:24 PM   #8
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Doesn't the Alpha I have a Prop Hub? I thought it did. IF so, that should be replaced and should be what protects the gears from shearing when this occurs.
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Old 08-06-2019, 06:09 PM   #9
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Quote:
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Doesn't the Alpha I have a Prop Hub? I thought it did. IF so, that should be replaced and should be what protects the gears from shearing when this occurs.
Yes it does but doesn't guarantee no damage will occur. From the sounds of it the prop shaft is bent as well.
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Old 08-08-2019, 02:19 PM   #10
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I can see how the prop hub won't protect the prop shaft if the hit is hard enough, but it should protect the gears. When a tooth shears, it sounds like a coffee grinder in gear.
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Old 08-08-2019, 02:33 PM   #11
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Thanks Shrew, When we hit the rock, we stopped and put it in neutral and I think it cut out itself. When we started it again, the engine appeared to be fine in neutral however would cut out almost immediately when put in gear. I think the lower it may be seized? We didnt get any sound from the Leg at all. Will try taking the lower leg off this weekend and report back.
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Old 08-08-2019, 02:34 PM   #12
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Doing some more homework on the unit before attempting to diagnose further. I had a feeling its going to be a lower leg replacement regardless as the prop pin is bent. Mike is probably right with replacing rather than repair. I wouldn’t trust myself to get it right and would only end up with money wasted and more tears. I fully expect to see gear shavings in the gear lube once I drain it.

My question is.. how can I tell if the upper part of the unit is ok and in working order? I’m guessing it’s a common occurrence for a leg to get hit. (My local marine parts supplier has the bottom leg as a best seller so I feel a little better knowing that.. LOL) So is there anything I can try with the bottom part removed to see if the top is intact? Provided I see splines on point #5 (See diagram attached) can I take it the upper block and rest of it to the engine is ok?
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Old 08-08-2019, 04:47 PM   #13
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You can check your upper gears by removing the top cap and looking into the upper gear case. It will be obvious if the gears are damaged.
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Old 08-08-2019, 05:19 PM   #14
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Quote:
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I can see how the prop hub won't protect the prop shaft if the hit is hard enough, but it should protect the gears. When a tooth shears, it sounds like a coffee grinder in gear.
I suspect the gears are not damaged but the shift mechanism is broke. This slides the dog clutch from forward, to neutral and to reverse. This would leave metal parts in the lube and with continuous running get into gear faces and bearings.
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Old 08-08-2019, 05:22 PM   #15
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Quote:
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You can check your upper gears by removing the top cap and looking into the upper gear case. It will be obvious if the gears are damaged.
Yes but since it runs in neutral and doesn't overheat that tells you the upper gears are turning to operate the water pump that's on the vertical shaft going down into the lower unit.
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Old 08-11-2019, 09:39 PM   #16
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Small update.. I ran the engine to see if it would start.. No problem starting but wasn't ejecting any water from the transom with the muffs attached to the bottom leg. Ran it for a good 2 mins and stopped it manually just incase I would cause any further damage. Hopefully its just the impeller that is wreaked or stuck..

I also drained the gear oil and saw lots of "glitter" in the drain.. There appears to be a magnet attached to the bottom drain plug screw, wiped it with a cloth and its pure shards (See screenshot) So yeah it's not pretty.

Had to stop there as I couldn't get the anode off to get the last nut/bolt. Hopefully will pick up the right allen key tomorrow and give it another try.

So whats the bets the top of the leg is also borked? (insert crying sound here :-) ) Is it possible to shove the hose up the upper leg water intake and see if it ejects water out the transom? Does the engine have some sort of coolant pump in addition to the impeller?

Thanks as always!
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Old 08-11-2019, 10:56 PM   #17
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If the impeller is not working the upper gears are most likely damaged. Did you remove the thermostat hose that comes from the transom to see if any water is flowing?
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Old 08-12-2019, 09:57 PM   #18
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Thanks Mike, Thats unfortunate news.. Whats the likely hood that the engine and crankshaft/splines are ok?

It may be a total leg replacement yet
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Old 08-12-2019, 11:18 PM   #19
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The connection at the splined shaft is the strongest in your drive train. All the teeth are theoretically in contact at once. In car applications, I've seen drive shafts and gearboxes destroyed but have not once seen damage to the splines on either end of a drive shaft or axle. Just my experience however and others may have additional inputs.
You can count on replacing the leg. Your prop shaft is bent, dog clutch isn't engaging, and sounds like your upper gears are not turning either. Rebuilds are not always successful and will be expensive. I recommend you determine your drive ratio and start looking for another leg.
If it were me, I'd have to take the upper and lower gears apart just to see the damage. I'm weird that way though.
Be sure to check your alignment with the leg off, the impact shock may have moved the engine slightly.
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Old 08-12-2019, 11:58 PM   #20
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Quote:
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Thanks Mike, Thats unfortunate news.. Whats the likely hood that the engine and crankshaft/splines are ok?

It may be a total leg replacement yet
If you can still run the engine in neutral look behind the engine to see if the drive shaft is turning. Even with this the coupler may have slipped to protect the engine. Only way to find out is replace the drive and verify you can still get on plane without the coupler slipping. If the coupler is bad the engine has to come out to replace it.
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