wt2

[WT2]

I have a Johnson 70 hp 1990. I have stripped out the splines on the drive shaft twice so before I replace it again is there any comments on why this motor has a week spot here. Is there a correction for this problem. I would have thought that the prop would damage long before stripping these threads. replacign this drive shaft is not a fun job so any help comments would be great!

 

[racerone]

Are you greasing the spline ??----Has this motor ever had an argument with rock or a tree stump ?---Are you shimming the replacement shaft properly ??

 

[bonz_d]

Have you looked at the splines inside the crankshaft? If you've damages 2 drive shafts already then chances are the crank is stripped also.

 

[WT2]

yes where I fish I have stumps that do cause issue but I almost always bumb them slow and and never has this killed the motor. I did grease the splines last time and as for looking at where they go into the motor it looks fine but I can't tell . I did not shim the last shaft but it set into the motor all the way in. The stripped threads go from about 1/16th of an inch from the top to the same in the bottom. I am wondering if there is supposed to be a system that protects this shaft when the prop gets bumped?

 

[racerone]

You can not replace a driveshaft in a lower unit without proper shimming of the pinion gear !!!-----If the exhaust housing is bent from impact the spline will wear due to constant flexing of the driveshaft.----If crankshaft splines are rusted / worn then splines on the driveshaft will wear quickly !!

 

[Chinewalker]

Once the driveshaft splines go out, they generally wear the crank splines a bit, too. The crank is hardened, so it will wear less, but it is also not stainless and susceptible to rust. So, bottom line is that you probably have worn crank splines, enough so that they aren't seated tightly on the driveshaft splines and are working them every time you shift gears, etc. until they spin out. Only fix is to replace the crankshaft...

 

[F_R]

The usual cause of stripped splines is rust. Rust in the crankshaft, that is. The drive shaft is stainless. Rust is caused by water getting in there. I'm not personally familiar with a 1990, but I assume it is supposed to have an o-ring or something to keep water out of the splines.

Yes, bent housings can cause it, but rust is way far more common.

Grinding up stumps and rocks is not the cause. But it sure is hard on propellers!!

EDIT: Yeah, I just checked the parts list and it is supposed to have a 310585 o-ring to keep water out of the splines. Not sure if it goes on the end of the drive shaft, or inside the crankshaft though. They've done it both ways over the years.

 

[WernerF]

O-Ring is in the crank on this motor. On the drive shaft below the splines you should see a dark ring where the O-ring has sealed.

 

[WT2]

No Title

I was thinking that the crank could have been a contributing factor as well. As usual this will be uncharted territory for me but what the heck that is why I bought a manual!! I have a bolt at the end of the shaft that does not look so correct to me. I would down load a photo but the computer says the file is too big The bolt is at the end of the drive shaft and seems to be riding on the shifter mechanism. The shifting seems fine. Also, the splines are worn, where the top has a little left and the bottom also has some left. Before I tackle the crank is there a way once I buy a shaft to test it for play in the crank. I would rather remain ignorant regarding the crank if possible? Thanks again for all the help.

 

[F_R]

Why dump money and time into it without having at least a good idea it is fixed this time. Pull the powerhead and inspect the crank splines, and by all means, put a new o-ring in it while you have access.

Your picture looks like the pinion gear bolt is loose---is it? That thing needs to be torqued to a specific value. Offhand, I don't know what that is, but somebody here probably does. Of course you can always check the manual.

And there is the shims topic also. If not correct, it can cost you a heap of money to replace stripped gears.

 

[racerone]

The pinion nut is loose !!!------That needs to be torqued to 40 / 45 FT-LBS.--------And that pinion gear needs to be put in the proper position with shims or gear life will be short !!!

 

[WT2]

yep the pinion bolt was just sitting there not holding anything down. It has been a few years since I put the thing together so I am not sure if it was torqued probably not considering the bolt was out. I know I didn't shim the pinion gear last time but I will read up on it and figure out the process. Since the pinion bolt was sitting loose could that be the cause of the shaft to strip the splines? Would there be any way it could have been the proverbial wrench in the gears? I was running 3/4 speed in open water when it went?

 

[WT2]

Ok I have had the new drive shaft shimmed which was way more costly than I thought it should be but I dont have the special tool for setting the shaft in so I will continue to gripe under my breath. I do see the o ring in the crank and also see where it rubbed on the old drive shaft. My game plan is to put it back to gather and treat it like a baby this summer. This winter I will have to tear is down and put a new or used crank in it. I can see that the splines are pointed so it will have to be repalced. At that stage I will see about new rings and honing the cylinders. I am a bit leery of a used crank and would love some comments on the issue. It would be great if there is a pressed insert in the crank system but I doubt I could get that lucky.