Scored Driveshaft Usable?

[Evinrude44]

Great information on this thread...

I'm having the same issue on my 1973 Evinrude 6hp Fisherman. It got to the point where the driveshaft would not turn in the upper gearcase cast-in brass (?) bearing. I later found water in the gearcase oil and the leak-path must have allowed debris/sand to migrate into the space between the bearing and driveshaft, scoring the two (see pictures).

My questions to you guys - are these parts still usable? When I place the driveshaft back into the bearing the fit is still pretty good (there isn't a lot of slop there). I know any amount of slop now allows the pinion gear to move that much more in the gearcase, but is there any way I can ream out the bearing hole and either install a new sleeve bearing (as previously mentioned in this thread) or attach a sleeve onto the SS driveshaft?

Is there another purpose to this bearing or is it only used to hold the driveshaft on axis so the pinion gear does not damage its teeth on the forward and reverse gears?

Thanks guys!

 

[F_R]

First, let me say that the bearing keeps the pinion from moving sideways as thrust is applied. Any sideways movement will throw the gears out of alignment and wear the teeth. OK, so you might be able to use the parts by polishing off the high spots, if there is no excessive side movement. But some might frown on that answer including possibly me.

The bearing is cast in place. A machinist with a milling machine probably could bore the bearing and make a new one to insert. I suppose you would have to evaluate the cost.

 

[Evinrude44]

Thank you very much for the reply F_R, I was hoping you would be the one to get back to be based on your answers in the thread.

Lucky I have a milling machine at my work and few co-workers who were previously machinists. I will ask them about boring the bearing and inserting a new one. For tolerance purposes, do you have an idea of a number that would define "excessive side movement"? 0.005"/0.010" difference between the ID of the bearing and the shaft diameter?

The other option I was thinking of was somehow inserting a ball/roller bearing like the later models use. It looks like I may be able to insert it on the other side of the upper gearcase (opposite the bronze/Babbitt bearing) or bore out the bearing and insert it there...I just need to determine if I have enough real estate for the latter. Have you ever heard of this done before?

Thank you again.

 

[racerone]

There are many ways to do this.----You could set up a boring bar to do this.----But you have to know the position of the hole to get the correct gear mesh !-----Or visit----maple leaf chapter----Fellow there made a fixture to do this job quickly and correctly each time.

 

[Evinrude44]

Thank you for your reply racerone, this community is incredibly helpful and you guys have been so fast to respond!

I was thinking I could determine the position using a standard center-hole finder and/or wiggler on the mill to determine the correct position of the bearing hole given that it is not beat up too bad.

Also, forgive me for being the new guy, but where can I find the maple leaf chapter? mlaoc.ca? Is there a post from the fellow who created the fixture that you are referencing?

Thank you again.

 

[Evinrude44]

I think I found the article you are referring to:

http://www.mlaoc.ca/technical-articles.html

The one by Peter McDowell

 

[racerone]

Correct.

 

[F_R]

I just quickly scanned my eyeballs over the article, but I agree, the lower bushing has to be aligned with the machined holes at the top of the gearcase. Seems the author went to greater efforts than I would have, but the idea is sound.

 

[racerone]

And I know from experience and setting up to do this work that most of these gearcases are BENT to some degree.----Adds another challenge to it when using holes under the water pump.-----Have a box full of 5.5 / 6 / 10 HP cases that need this kind of work.

 

[Tim Frank]

Check one of the salvage yards to get the cost of a decent gearcase housing.
Then you can compare to the effort and cost required for machining and rework.
As has been pointed out, the machining is very simple....I have the tools and ability to do that myself.
The challenge is properly locating anfd aligning to bore out, ream, and rebush. I'd be out....man's gotta know his limitations.

As an old tool and die making guru I knew would say when faced with a truly difficult job..."not a job for beginners."
Really meaning that he needed all his 40+ years of experience.

There will be a max tolerance for "on-centre" AND degree of parallelism between two centre lines.
Not a job for beginners.

 

[Evinrude44]

Thanks Tim, I was actually lucky enough to find a new gearcase housing for my engine on MarineEngine for $80...and given that the cavitation plate is also damaged on my current gearcase I'm going to pony up the dough and buy it. The issue still remains with the scored drive shaft and all of the used ones available online are showing similar wear patterns to mine.

I think what I'm going to do is put the whole thing back together after I receive the new gearcase housing and reassess the damage.