Knocking sound from my Alpha One Gen 2

[nennedk]

My Alpha drive makes a knocking sound (it can also be felt in the hull) that It hasn't done before. I have owned the boat 10 years. On land on muffs, when put in forward or backward gear a knocking sound appear as heard on attached file. Does anybody have an idea what it could be? I have been told its probably because there is no load on the propeller, but as said, it haven't done that before. The mechanics I've spoken to don't have time for another month or so.

 

[Scott06]

Hard to tell from here but my first place to start would be pull the drive and check gimbal and ujoints. Also drain drive lube and check for metal.

 

[nennedk]

Did pull the drive last weekend. No signs of ujoints hitting something. Has just filled the drive with oil after winter storage. There's was no debris when unloading oil and it passed the pressure test. How to check gimbal and could it be it when the knocking is only there when in gear?

 

[alldodge]

I think it's in the drive, something has loosened inside and/or chip/broken gear tooth.

What does the gear lube look like?

 

[nola mike]

Gimbal checked just by feels. Ujoints ime can still feel ok but be bad. Did you store the drive without oil? First thing would be to drain/check for metal, pull top cap to inspect gears, and pull the drive and run the motor off a hose to try to isolate the problem a bit more.

 

[Scott06]

Agree with others take the cap off and look split the drive.

as a sanity check maybe run the engine with drive off to verify the noise is gone with out the drive turning. can stuff a garden hose in the water port on the bellhousing to do this.

One thing ujoints can be tough to diagnose by feel unless they are really f'ed. On my gen 2 with the permalube ujoints they felt fine but i relaced them while it was apartand one or two crosses on each joint had ridges worn in them. Might be worth checking if you dont find anything in the drive.

I found my drive had a corroded upper bearing just under the cap. It had sat for most of its life before i got it (11 yrs old and 37 hrs...). So that bearing is dry in storage can corrode easily

 

[Grub54891]

Had one at the shop that did that. Tested with a different drive, noise was still there. Tried it with no drive on it, noise was still there. Coupler wasn’t hitting anything and was fine with alignment. Never did figure it out.

 

[nennedk]

Agree with others take the cap off and look split the drive.

as a sanity check maybe run the engine with drive off to verify the noise is gone with out the drive turning. can stuff a garden hose in the water port on the bellhousing to do this.

One thing ujoints can be tough to diagnose by feel unless they are really f'ed. On my gen 2 with the permalube ujoints they felt fine but i relaced them while it was apartand one or two crosses on each joint had ridges worn in them. Might be worth checking if you dont find anything in the drive.

I found my drive had a corroded upper bearing just under the cap. It had sat for most of its life before i got it (11 yrs old and 37 hrs...). So that bearing is dry in storage can corrode easily

No knocking sound when not in gear. But knocking sound in both forward and backward gear

 

[nennedk]

I think it's in the drive, something has loosened inside and/or chip/broken gear tooth.

What does the gear lube look like?

I think it's in the drive, something has loosened inside and/or chip/broken gear tooth.

What does the gear lube look like?

When i took oil off last season it looked fine with no debris. And then filled fresh oil 3 weeks ago but i will drain it and have a look. I can add to the story that i hit a stone last season so my stainless steel prop took a hit, but didnt feel anything wrong rest of the season, but i suspect something has happend anyway

 

[nennedk]

Gimbal checked just by feels. Ujoints ime can still feel ok but be bad. Did you store the drive without oil? First thing would be to drain/check for metal, pull top cap to inspect gears, and pull the drive and run the motor off a hose to try to isolate the problem a bit more.

Yes. Did store the drive without oil. I will check oil

 

[nola mike]

Yes. Did store the drive without oil. I will check oil

The order to do all of this in, as mentioned above:
1. Drain oil. May not have shavings in it if it was just filled and hasn't been run much
2. Take off top cap and look at upper gears. Those gears/bearings can rust/pit if stored dry
3. Run motor with drive off, to confirm that that's your problem.