Shaft Resistance

[sandpiper10471]

Headed out for a sail last weekend and encountered a lot of vibration when motoring at higher (but nowhere near max) rpm's. There was almost immediately a smell of either hot rubber or hot oil so babied her along at 1800.

My thought was the engine had gone out of alignment but when I started taking off the drive saver coupler, I found the shaft very hard to turn. First thought - transmission problems. With the coupler undone, the tranny turned freely but the shaft is still very stiff. Still a good drip at the stuffing box.

Does anybody have any ideas on this? I haven't wrapped a dinghy painter or hit anything. Then engine does not appear to have moved at all. A few days at the dock and the problem developed. Moral - don't sit at a dock! But
I do need to solve this situation.

 

[timvg]

We had a similar problem a few years back. The shaft was virtually impossible to turn by hand and when we were powering, the stuffing box would get hot to the touch. We had the boat hauled and the strut had to be removed and re-alligned. The engine was not out of allignment and the shaft was not bent.

Just one of those crazy things that we had to take of and we were never really sure what caused it. The only thing we could think of is that about a year earlier, our boat was re-launched using a crane and I saw them attach a rope to the strut to help guide it in the air. Maybe that's all it took to start a bad strut allignment.

 

[Ed Schenck]

That's rough Bill, hard to see how you can resolve it without a haulout. You might want to dive on it or have someone go under just to be sure you haven't wrapped something around the shaft. But the fact that you were smelling something would seem to indicate a problem with the stuffing box or shaft log.

There are three points of resistance. From the inside out: the stuffing box, a misalignment causing the shaft to rub on the shaft log, and the strut cutless bearing. The zinc sliding down against the strut might cause some resistance but it wouldn't cause a burning smell. I think the first step is the dive and then taking the stuffing box apart.

Disconnect the stuffing box at the hoseclamps without first loosening the locknut. Slide the box up from the hose and see if the box is the culprit. You can stop the waterflow with some well-placed rags. If the shaft still turns hard and it is centered in the hose and stern tube then it has to be the cutless bearing/strut.

 

[sandpiper10471]

Thanks guys: I did the dive and found nothing on the shaft or cutlass but I was able to hammer the shaft back (kinda gently) in order to separate the coupling. Then after loosening the stuffing box till water flowed in I was able to turn the shaft relatively easily. That is the good news. My opinion is that the face alignment is off at least an eighth in. to starboard. This after having the engine re-mounted for about a thousand dollars! I think the rubber smell was the red flex coupling heating up. Other problem now is that the flex coupling is a half inch wider or so than the metal coupler so to make sure there is perfect face alignment I feel I have to remove it - especially if it is damaged. (Can't see any now while it is on the tranny.) To get the flex off, I will need to remove the original coupler from the shaft. (not enough room to remove the bolts) Then when the alignment is done, re-install the flex coupler if it is still any good. And the 37C was not built for inflexible geriatric non-mechanic types! So I would like to avoid the removal of the flex insert if possible. Any experience out there aligning with the flex coupler installed?

 

[Ed Schenck]

Aligning with shaft-saver.

Not sure that I understand the problem. Are you suggesting that the shaft-saver(flex coupler) is not square? I mounted the shaft-saver and then aligned the shaft flange to that. Just as I would have aligned it to the tranny flange.

 

[sandpiper10471]

Re: Aligning with shaft-saver.

The problem as I see it is that the drive saver is 4" diam. and the coupler 3". This makes it harder to see if the face alignment is right on. Yes, it is the same kind of setup as in your photo.