Gearbox with worn bushes

[Bergie]

I was suspicious of my Century 100 gearbox leaking oil in large amounts, especially when the motor is lifted up. After some test tank runs, I checked the oil levels, and as was said once, "if its not leaking oil, its not a Seagull--- or empty. Mine was empty. I pulled of the gearbox and form the motor and a diagram from internet and discovered a few things, some of them not belonging in the box. My problem with the oil leak was the pinion gear bush. Its really worn and the pinion is wobbly. I tried my best to get the bush out with the pinion, but gave it up, even after heating the gearbox. I finally decided to stuff a brass shim into the brass bush. It certainly stopped the wobble. And the oil dripping out when I tilt the motor. The fit is pretty tight, but the problem is the shim don't go all the way through the brass bush, its simply too tight. I acknowledge this as a temporary repair and the jackpot will be to remove the bush and replace, perhaps custom made to fit the shaft of the pinion.

Now the pinion do have some wear on the tips, most likely from slipping over the crown gear. And this is where the extra parts appear. On the forty plus gearbox, part #12 is brass according to me, but there was/is an extra steel washer added. I removed this washer since it appears to have cut quite badly into the brass seal/bearing part #13. The problem was that then whole crown gear and shaft moved back to such an extend that when holding the drive shaft, the pinion starts to slip. Is that just normal wear on the brass bushes or some other misalignment? There was another steel washer on the other side of the crown gear. I suppose it was to prevent the crown from pushing too hard into the pinion?

Is this gearbox worth repairing with so many worn parts? What should I be looking out for?

[John@sos]

Sadly these gearboxes do not fare too well if starved of oil!

There should be a steel thrust washer behind the crown wheel to kep the teeth engaged, without it, or with a worn one, the teeth will suffer, fairly quickly!

I do have a selection of used FP and Century boxes, that are not stripped and checked, but that turn without noise or stiffness. that will be cheaper way that replacing the bevel gear or a pinion, bearings alone are £33.50!

Contact me and I wil see what I can do.

Regards,
John
SOS

[dev7]

Bergie,

I am looking for diagrams for the forty plus gearbox (and the propellor if possible). could you point out where to find them?

In any case here is my problem:

This forty plus model 55 was recently handed over to me. And some pieces have possibly been moved around. Yesterday the engine started making real ugly noises-propellor not turning. I opened the gearbox, and found out that the crown wheel was slightly worn (even though I think and hope that it will still function). After some experimentation, I decided that the washer inside was too thin, and replaced it with a slightly thicker washer- that also came with the engine.. Now the gearbox will close, yet with a slight gap.

Tomorrow I plan to test ride..but I am not a hundred percent sure if this is the right solution.

Could someone please explain how the gearbox functions. And list the pieces that are found inside? A diagram would greatly help. Additional information as to the pieces on the other side would be greatly appreciated. Thank you, happy riding



dev

[John@sos]

Sadly I cannot post all the pages from the spares books as they are copyright.

The Spares book is available from me with exploded diagrams etc, £7.50 plus postage, get in touch via the web site.

There is a thick thrust washer behind the crown wheel, between it and the cap, or there should be, otherwise the gears will not mesh and will chew them selves to bits in no time!

Hope this helps,
Regards,
john
SOS

[RickUK]

Bergie - as John is saying there is a thick thrust washer which fits at the back of the crownwheel. If this was fitted before,it is often 'stuck' to the gear by oil and not immediately obvious - this washer is about 2mm thick.
Some endfloat is essential - the gears should not run tightly meshed, as with any gear pair.
There was a way of measuring endfloat, which was to leave the brass collar at the outside/back of the gearcase off, and with the crownwheel, thrustwasher and endcap fitted, the endfloat (axial movement) of the propellor shaft measured, and thinner shimwashers could then be added in addition to the thick washer to give the appropriate amount of endfloat.
Regret I don't recall the amount of endfloat! This is all probably irrelevant anyway with gears which have a degree of wear - as long as you have the thrust washer in the correct place and the teeth on the pinion (which would have the most wear) and the crownwheel are in reasonably in good condition all will be OK. If the gearteeth a badly pitted (corrosion holes on the tooth surfaces) the gears aren't going to live much longer.
Worthwhile getting a spares book from John so you can see the layout of the parts etc.

Rick

[dev7]

One shimwasher can make wonders.. I think now that everything on this seagull is in the right place, and I have solved the puzzle. It works and never halts...well so far. Thank you (John, Rick and Charles) for all the quick responses. One more old seagull saved...

there seems to be a minor problem. It is perfectly ok in half throttle but I don't think I get more power when I do full throttle. It even feels a bit slower. No weird noises, so I assume that it is not gear related. Could it be the spark plug..? Could it be missing cycles (is this called 4 stroking?) thanks...

[Bergie]

I've been a bit busy with my other pet project, a PVC dolly for my canoe. Will be happy to explain the dolly plan if anyone interested.

Back to gearboxes... I understand the thrust washer is steel? Mine was brass washer against crown gear and steel washer at back of gearbox. I think the steel washer was a problem, the back of the shaft have quite a bit of wear, i.e. grooves around the shaft. So much so that I had to smooth the shaft a bit with sandpaper. As a result the lip of the brass bush at the back of the gearbox seems worn down. It even had a sharp lip fitting exactly inside the steel washer. I replaced the steel now with brass only since its much softer and unlikely to eat a bit of shaft. I do have a tiny bit of "endfloat" after closing the gearbox. Without the shim around the pinion shaft, the pinion wobbles away from the gearbox. So I took a "happy go lucky guess" at how much endfloat I need. In the end the thick brass thrust washer plus two 1mm (more or less) brass washers for shim feels about right. One less washer and the gears tend to slip and bind as it climbs over each other, one more, and the gearbox won't close.