Propshaft side play

[Matthew A.]

I recently replaced all of the lowerunit bearings and seals. I was able to adjust the end play of the propshaft to about .002" to .003" by installing a forward gear thrust washer of correct thickness. With use this play has increased to .007" +/- .001". However, the propshafts side to side play seems to be increasing with use. At time of rebuild, the side to side play if measured from end of shaft at prop nut threads, was probably .015" to .020" in either direction. Currently side to side play maybe more then double. I realize this increase could be due to improper propshaft diameter @ bearing contact surfaces. However, could excessive wear of the bronze sleeve that is pressed in the forward gear also cause side to side play of the prop shaft?

Lower unit is single exhaust, single drive shaft, engine model number 856X8B
Hours on lower unit= less then 70 hours

 

[Frank Acampora]

Re: Propshaft side play

Since the prop shaft sticks out of the bearing approximately as far as the distance from the rear bearing to the forward gear, any wear of the bronze bushing will be reflected in side play of the prop end of the prop shaft.

It is unusual for the sintered bronze bushing to wear because:

1. It is very hard. Try drilling or cutting one sometime.
2. Sintering presses powdered bronze together under tremendous pressure with heat and fuses the metal particles. This produces a porous piece that absorbs and holds oil very well
3. The prop shaft is only turning in the bronze bushing under no load. They only move in relation to each other during neutral and reverse operation. During forward operation (which is the greatest running time) The forward gear and prop shaft are locked to each other by the drive dogs.

This is not to say it can not happen, only that it would NORMALLY be a slow and unusual process.

The forward gear tapered roller bearing is only held into the outer race by the pinion and thrust loads on it during forward operation. During neutral and reverse there is always a bit of slop in it which would also show up at the prop end. To check prop shaft side to side end play you MUST pre-load it (push in the prop shaft hard).

BTW: in and out end play of the prop shaft is normally supposed to be .007-.010. A bit tighter won't hurt it unless you have 0 play at which point the rear land on the prop shaft (which keeps it from pulling out through the reverse gear in neutral and reverse) Will contact the reverse gear causing steel on steel rubbing in forward gear with wasted power and eventual wear.

 

[Matthew A.]

Re: Propshaft side play

Thank you for replying Frank,

I am hoping that the side to side play I am noticing is due to settling in of the components after the rebuild. It doesn't seem to be getting any worse after an additional 25 hours or so of use. While doing the rebuild, I noticed that there seemed to be quite abit of play of side to side of the forward gear upon the prop shaft with the components in hand. Looking closely at the bronze bushing I could see wear of the bushing in the form of small grooves. However, considering I could find no information regarding the replacement of the bushing, I came to the conclusion that any side to side play of the prop shaft would be something I would just have to learn to live with. I am wondering, if side to side play is reduced while the prop is turning while in forward gear due to thrust created by the propeller pushing the prop shaft against the forward gear and it's bearing assembly? Thrust then keeping the shaft square against the forward gear thrust washer and forward gear.