SEI Alpha 1 Gen 2 lower ratching noise (with video)

komodo_goods

Seaman Apprentice
Joined
Dec 31, 2023
Messages
34
Good evening all. I recently installed a new water pump and shift shaft bushing. Now, I have ratching in the lower unit that seems to come from the shift crank, spool or propeller shaft. I've attached a video for reference.

Is it possible the shift crank or something shifted when I pulled the shift shaft out to replace the bushing?

 
Last edited:

cyclops222

Lieutenant
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Mar 21, 2024
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1,289
No way I can do it from my computer.
Did you accidently NOT get the bushing into the correct location ?
 

komodo_goods

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Dec 31, 2023
Messages
34
No way I can do it from my computer.
Did you accidently NOT get the bushing into the correct location ?
The only bushing I replaced is at the top of the shift shaft. Like in the below picture.
No way I can do it from my computer.
Did you accidently NOT get the bushing into the correct location ?
 

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alldodge

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Mar 8, 2009
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42,054
Yes normal for the Alpha drive, it's the dog clutch
Bravo drives won't do it because they do not use a dog clutch
 

dubs283

Vice Admiral
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Jul 27, 2005
Messages
5,322
Are you saying this is a normal operation?
Yes

The propshaft should lock CCW in FWD gear and ratchet CW. Lock CW in REV gear and ratchet CCW. Spin freely both directions in NEU

This is due to the design of the clutch dog and gear face teeth being ramped
 

komodo_goods

Seaman Apprentice
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Dec 31, 2023
Messages
34
Guys thanks for the assistance. I also just watched a video of the drive in operation and now understand the theory of operation. The prop is over running the clutch dog teeth because there is no water pressure against prop helping seat it into the gear which is causing the popping. I'll get her reassembled and hopefully on the water today or tomorrow
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,291
think about this . prop turns clockwise in fwd when under power. If you were to turn the input shaft clockwise you will see the prop turn clockwise for fwd gear.
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
That is why they say never run the boat with the outdrive up.
I have the same set up. It used to worry me too . That was 3 years ago.
 

frostystorm

Cadet
Joined
May 22, 2023
Messages
21
Guys thanks for the assistance. I also just watched a video of the drive in operation and now understand the theory of operation. The prop is over running the clutch dog teeth because there is no water pressure against prop helping seat it into the gear which is causing the popping. I'll get her reassembled and hopefully on the water today or tomorrow

It has nothing to do with the water pressure. The teeth of the clutch dog are ramped, they are meant to ratchet in the opposite direction.

s-l960.jpg

When the clutch dog is pushed into the rotating forward or reverse gear, which has a similar design, it will turn and seat until the flat parts mesh.

They ratchet so that they have reduced wear from shifting rapidly from forward and reverse during docking operations, where most weekend pleasure boats spend most of their shifting time hah.

When you turn the prop clockwise without also turning the drive shaft, the clutch dog is riding up the ramps of the forward gear until they fall back into place. This is also why rotating the prop during drive installation will make your gear selector move out of place, the gear selector lever sits in the middle of the clutch dog in that slot, and when it walks up the ramp, it pushes it away rotating the rod the shift selector is attached to, and misaligning your selector foot, thus making the drive impossible to install that last inch or so, and then you curse out your buddy for twisting the prop the wrong way while putting the drive back on trying to line up the splines.
 
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