cutless bearing/alignment

Wondering if you guys could tell me what you would do in this case:

I hit something last year and had my Stb strut straightened, new cutless bearing and alignment on both sides. Shafts are both centered in the shaft logs.

In the process of aligning the port side engine and getting the shaft centered (it was way off, almost touching), the shaft became a lot harder to turn by hand. It was probably like this for years and the alignment caused the shaft to wear in a different part of the bearing.

After putting about 40 hours, it's loosened up quite a bit but it's still tighter than the Stb side. I don't have any play or vibration. By "tighter" I mean a good one handed pull on the prop. I pulled both props off and can rotate the shaft with my hand on the Stb side but can't on the port side. With the prop installed, I can. I'm assuming the new bearing vs old probably accounts for some of the friction as well.

By the book, I think the strut needs to be ever so slightly adjusted and then I would install a new bearing at the same time. I really wanted the shaft to be centered in the log and could probably adjust it closer if I was willing to have it off center.

With no play, would you guys leave this alone and maybe deal with it next year?

Bob

Based on your description, the only issue you have is inefficiency due to the extra friction. Its the time-vs-money discussion. Fix it now and it will cost xxx, defer it and you could wear the bearing prematurely and start on the shaft......

If it's not a huge effort, i'd do it over the winter. If the strut's mounting plate is set in pockets in the hull like mine (flush mount and 'ultra smooth') I'd entertain tweaking the strut, if possible or deferring it. It takes me the better part of a week to get those 'pockets' filled back in and the hull true in that area. (to me huge means the adjustment is up and down so the strut HAS to come off; a tweak would be to move the shaft 1/8" inboard at the log by twisting the strut bearing.)

bobct said:

Shafts are both centered in the shaft logs.




With no play, would you guys leave this alone and maybe deal with it next year?

Bob

Click to expand...

Centering in the log is not the goal, it is to center the shaft in the cutlass. FWIW, one of my prop shafts is like your tight one; been running fine for 10 years now.

diver_dave said:

Centering in the log is not the goal, it is to center the shaft in the cutlass. FWIW, one of my prop shafts is like your tight one; been running fine for 10 years now.

Click to expand...

Dave is right. As long as the shaft does not hit the hull, and has some clearance, the shaft alignment in the log is not a real issue. What is important is the shaft alignment both in the bearing and at the coupler. I would not sacrifice a proper bearing fit to have it centered in the log. If you can tweak the strut so all the stars aligh, that's great but I wouldn't lose sleep over it.

I'm guessing you are doing this on land.
1. A dry cutlass will be harder to turn.
2. The hull will flex slightly when on blocks compared to in the water

A couple years ago, i found the snapped off flush with the stringer forward mounts' lag bolts.

After the fun of replacing them, i adjusted the mounts to get the "coupler alignment" dialed back in. The shaft was like Bob & DD described - tight. when we hauled it a week later it required two hands on the prop to turn it, not one hand. intermitteantly, the shaft would 'squeal' while in gear at idle. Would up recentering the shft in the log and moved the engine/gear to get the coupler happy...no more 'squeal.'

I know my running gear is oversized 1.5"od shaft so it is a bit stiffer than most. the point is when the shaft gets harder to spin, the friction it sees has increased and you may be close to edge of its operating envelope (adjustment may soon be required).

thanks guys, a few things to think about. Yes, I am doing this on the hard and assume it's better in the water than it is now but my reference point (other side) would be as well.

My struts are surface mounted onto the hull and secured with six bronze bolts with a metal plate/nuts/washers on the inside. It is a very slight tweak side to side (less than 1/8") the height is fine. I assume it has factory fiberglass shims underneath like the other side.

I'll take a closer look and see if I want to tackle it now. It doesn't sound like a huge deal if I did nothing....

Bob

centering the shaft in the log is still a good idea. You do not want the shaft to ever rub and wear threw the shaft log bronze and this could cause a big leak. Shafts that are less than 1.5 inches tend to flex a little anyway as they spin.
A thick 2 inch shaft is a lot stiffer and alignment is more critical.

http://www.yachtsurvey.com/Alignment2.htm

A conventional shafting system is essentially a free-floating, semi self-aligning system. How's that? Well, because the engine is mounted on rubber mounts, and the shaft is mounted in rubber bearings. Of course rubber being soft, that means that both the engine and shaft can and do move. See my point here? Since neither the shaft nor the engine is held rigidly in place, there's not much point in attempting to perfectly align the shaft with the engine, is there? No, because if everything is approximately aligned, the shaft will tend to self-center as a result of centrifugal force. The fact is that conventional shafting systems will tolerate a great deal of intolerance because of these factors.

Click to expand...

An extreme misalignment will wear the transmission bearing. It might even cause the prop shaft to break in half where it meet the coupling. The stress corrosion SS shaft can flex and crack and the crack can propagate threw the whole shaft. As it spins it is being stressed in a continual arc and the weak point is usually at the engine keyway.

As a general rule, shafts under 1.5" tend to be self-centering because they will bend so some small degree. But shafts larger than this do not take well to bending. They will not bend but work to tear the system apart if not correctly aligned.

Click to expand...

my 1 3/8 inch diameter 10 foot shafts when I was reinstalling I noticed they were like big springs. One end held by the strut other end free in the air. I was very careful not to let them hang and used dish soap to aid in sliding it back into place. So most definitely, I can understand it will self center and move around under engine torque.

Also since the engine, shaft log, strut are part of a slightly flexing bottom under loads from wind wave and engine, I wanted my shaft log centered as close as I could get it. My shaft logs had worn dangerously thin over the years where the shaft had been rubbing. I ended up repairing it with silver braze, building the worn area back up and reinforcing it. Surprisingly, the prop shaft showed ZERO wear where it had rubbed almost threw one shaft log.

I think they are some kind of Aquamet SS shaft. The shaft logs are bronze with rubber hose connected to the seal.

The shaft seals are not that awful hard Teflon flax wax. I used
http://www.gore.com/en_xx/products/sealants/packing/gfo_packing_fiber.html
This is really great stuff. NO LEAKS at all, not even a little bit. And it lasts and stays cool.

My shafts were not perfect where the old style flax packing sat. I had a little bit of pitting which I filled with some loctite epoxy.
buy marine packing here
http://www.emarineinc.com/index.php?cPath=49