9.9 merc - broken drive shaft (twice now)

[jmanng]

we have a 9.9 merc that snapped the drive shaft (just above spline on bottom end) because we had failed to do proper maintenance for a number of years (no lube in bottom end). So we bought a new shaft and re-assembled it (added lube). Everything seemed to be settled in properly and moving freely in forward and reverse when re-assembled but the new shaft didn't last 10 minutes. snapped in the exactly same place.

So we don't understand what is happening as we did have an explanation for what happenned in the first place? We've heard that there is a bushing done in the lower unit that centers the shaft and wondering whether maybe it's mashed... but everything was moving pretty good. also been told that it can't be replaced...

appreciate your insight in this matter,

TIA,
Jaime
90-91 mercury 9.9, serial no. is 0D065899
ontario, canada

 

[tx1961whaler]

Re: 9.9 merc - broken drive shaft (twice now)

we have a 9.9 merc that snapped the drive shaft (just above spline on bottom end) because we had failed to do proper maintenance for a number of years (no lube in bottom end). So we bought a new shaft and re-assembled it (added lube). Everything seemed to be settled in properly and moving freely in forward and reverse when re-assembled but the new shaft didn't last 10 minutes. snapped in the exactly same place.

So we don't understand what is happening as we did have an explanation for what happenned in the first place? We've heard that there is a bushing done in the lower unit that centers the shaft and wondering whether maybe it's mashed... but everything was moving pretty good. also been told that it can't be replaced...

Hit anything lately? Has the motor been dropped? Sounds like a bent midsection...

 

[Mi duckdown]

Re: 9.9 merc - broken drive shaft (twice now)

Without a serial number of the motor you will have No Luck.
There was a time when Merc changed from bearings to brass bushing where the drive shaft went thru the lower end. They had problems. There was a bulletin on this. Now this was back in 1980 + And was replaced with bearings. But the shaft never snapped.??? Never seen anyone snap a drive shaft. And I run some ruff water. Seen prop shafts bent and twisted. But never a drive shaft.????

 

[jmanng]

Re: 9.9 merc - broken drive shaft (twice now)

serial no. is 0D065899

as far as I know, the unit did not hit anything in the water when it was being used (nephew) and the motor has not been dropped. everything (bottom bolts) line up and screw in by hand and no other evidence of any twist, so I really don't thing its bent.

the shaft in both cases snapped just above the splines on the bottom side where the shaft is a wee bit smaller in diameter (so I guess by design, it's the weakest spot).

Thanks,

 

[jmanng]

Re: 9.9 merc - broken drive shaft (twice now)

Must be a spun bushing... I can't figure anything else.

Mi duckdown, can you point me to where I might be able to find the service bulletin you made mention of? Mercury parts express now bans canadian ip's from accessing their site (no doubt canadian dealers have complained about losing sales to them and other online outlets... too bad, they should be fair in their pricing).

Thanks,