Mainsail outhaul gearbox

Mike Ondra

I know others have had difficulty extracting from the gearbox the shaft that drives the gypsy, an operation that often requires some significant force. After neglecting to lubricate that shaft for a year or two (maybe more) I had the same problem. Tensioning a halyard to the top of the shaft and some aggressive upward pounding with a sledge hammer succeeded in breaking the top plate of the gearbox. While this facilitated partial disassembly of the gearbox in place, we are left with the core of the gearbox and the gear still in place and frozen to the shaft which remains through the boom.


Proposed next steps:


1)      Remove the large gear from the core. It was not obvious to me how that gear is splined to the core. Can that gear be extracted downward with a gear puller?

2)      After removing the gear, my thought is to expand the core by heat which hopefully will then allow the shaft to be extracted.


Thoughts and suggestions? This is the Leroy Somer MVA M33C gearbox.


Suggestion to others, remove and grease the mainsail outhaul shaft at least once a year.


Mike Ondra


Rock Hall, MD

amelliahona <no_reply@...>


I feel for you but I hope you don't make a bad situation worse.  I pounded on my shaft with a bolt screwed in the bottom until I thought I would damage the boom and then sought help.  What is needed was a too that rather easily "pushed" the shaft upwards.  It was a unique type of "pusher" as opposed to a "puller".  I seem to recall a photo of the device somewhere on the forum.  Basically it is a bar of steel that inserts transversely thru the opening in the gearbox mounting bracket that is below the boom.  Shims are placed under it to bear on the upper surface of the gearbox shaft (the hollow shaft into which the solid shaft seats and drives with a woodruff key) and then this is tied with bolts to a bar parallel to the upper one that is below the gearbox shaft.  A threaded bold is screwed thru threads in the lower bar such that as the bolt is screwed in, it pushes up on the shaft (with a protective piece of metal in place so as not to damage the shaft end).  Counter pressure is supplied by the upper bar of steel [basically a puller in reverse].  A picture would be worth a thousand words here.  

Please remember that aluminum remembers every stress and will fatigue fail if stressed to much from pounding etc.  That is the reason it is so important to have the pressure on the shaft bear on the gearbox receptacle shaft (steel) rather than on the aluminum cover of the gearbox or worse yet on the boom and its bracket.


Find someone with the right "pusher".  In my case after I spent hours pounding, penetrating oiling etc. the mechanic I consulted had the pusher in his shop and extracted the pin in 10 minutes. 

I wish you the best, 

Gary S. Silver 
Amel SM #335
Fajardo, Puerto Rico   Puerto Del Ray Marina


Hey Mike -

Sorry to hear about your troubles... I too have been a victim of this process and due to "lack of maintenance" (no offense of course). Just to be clear and so I can paint a better picture in my head. There are two "plates" or covers that also house a seal on the top and bottom of the transmission... Was it this piece which broke? 

Does the transmission spin when the out haul motor is engaged? If not does it spin at all or is it completely seized in its place? 

From what I remember, there are two gears. A worm gear coming from the motor shaft, and a main gear attached to that stainless steel shaft that your Andersen shaft runs through. That stainless steel shaft also has 2 large race bearings and a few locking snap clamps. 

Please provide a few more details and I will do my best to help you out. I know if I cannot you will have no problem getting responses/advice from some of the more experienced members on this site. 


Bill Maffei 
SM #195
It's all Good

amelliahona <no_reply@...>

Here is a link to the "Pusher" tool 

Hope this helps.  I have some photos of the disassembled outhaul gearbox in a folder in the photos section.

Gary Silver
s/v Liahona
SM #335 



Hi Mike,
I got it out by disassembling the boom, taking it from the boat and solid punching,
you need to put the support in the right place, otherwise you might brake something you don´t want to brake.
If you turn the boom upside down, the support of the boom should be at the hollow output shaft, the one to which the stainless shaft is connected (with a little key). Slide two solid metal bars side by side under the hollow shaft and support them, so there is no load on the boom or the gear box housing when punching.

I´ll put the exploded view of the gearbox in the files section under Leroy Somer Gearbox.

If you work with an shaft extractor it´s the same thing: you need to put the support/metal bar of the extractor to the hollow shaft.

Good luck!

Walter (Noa, SM2K 436)