Propshaft End Float

[Gannet]

I am about to set up the gear meshing of my Forty Minus (SJM).
Am I right in thinking that the end float should be 0.005" to 0.015"?
Is this achieved by fitting different thickness through hardened thrust washers?
Would they need to be surface ground to the required thickness?
Can shims be used to achieve the required end float?
Thanks.
Jeremy

[1650bullet]

I am about to set up the gear meshing of my Forty Minus (SJM).
Am I right in thinking that the end float should be 0.005" to 0.015"?
Is this achieved by fitting different thickness through hardened thrust washers?
Would they need to be surface ground to the required thickness?
Can shims be used to achieve the required end float?
Thanks.
Jeremy

I wouldnt worry about Meshing--surface grinding or shimming, Just put it all back togehther using what you got now. If theres to much end float,You can remove the gearcase cover gasket and use silastic instead, That alone can give about 8 to 10 thou to close up the gap if need be. Dont know how old your (SJM) is. But my LLS is 50 years old with all original gears in it. So over a period of 50 years, something is going to have a bit of wear and tear in it. So removing the cover gasket is all you would probably need to make eveything take up. If you can grab the end of the prop shaft with your fingers, and you have a tiny bit of backlash, Just leave it. Its not a racing motor. So nothing will happen.

[Gannet]

Thanks for that advice.
My SJM is 1955/6.
The gears look ok, but somebody has put in shims of 0.75 dia in lieu of 1.0" which has locally worn the bearing in the end cap producing a lot of backlash. I thought that I if i was going to put in the correct dia thrust washer I might as well get the thickness right. I have since found that an 0.084 thick washer gives 0.008 backlash, which I guessed feels about right(?).
Following your comments, I think that is probably ok.
Thanks again.
Jeremy

[Charles uk]

Yes it is adjusted by the use of the hardened steel ground thrust washers, they come in 3 thicknesses 12, 13 & 14 gauge.

As 1650 states quite correctly your crown wheel & pinion will be worn, as will be the thrust washer & the thrust face of the bronze bush in the end cap & you can remoce the paper gasket & replace it with RTV or similar, to decrease the clearance by 10 thou, ish, which is the thickness of the end cap gasket.

If your going to adjust it check it out before you refit the gearbox by spinning the prop like your trying to start a model airplane engine, after oiling the gears & bearings & adjust until it's at it's smoothist in terms of noise.

Seagull gearboxes will run for a long time in an allfull state, ask Jan the Dutchman how many hours has his box been making a noise like that, you can hear the whine from 20 meters away when he motors past you!

[Gannet]

Thanks Charles,
The smaller dia (0.75") thin shims that had previously been fitted in lieu of the thrust washer have worn the end bearing face locally.
SOS John has been on hols so I haven't been able to contact him, so thanks for the details of the thrust washers. A 13 gauge (0.092) or 14 gauge (0.080) would seem to be about right.
I won't be able to spin the prop as you describe, as the drive shaft is connected - but thanks for the idea.
Cheers,
Jeremy

[Charles uk]

Your gears will be worn allready! it's the only way to tell if it's running without too much noise or drag.

[Gannet]

yes, I can see from your explanation that turning over just the gearbox is the only way to tell. i will now remove the gearbox and give it a go.
Thanks for your advice.
Jeremy