prop shaft tube and shaft

[letterman]

The damage is that the shaft tube is missing about 7 inches of one side of the shaft tube. A friend (engineer) told me I don't have to replace it. Oh yeah, a huge chunk of the glass around the shaft exit area is missing owing to the shaft bending sideways out the hull after hitting a submerged piling. So there is some fiberglassing that needs to be done. He contends that that fiberglassing will suffice. I seem to think that a whole round shaft tube would have more strength because of the chemical bond vs the mechanical bond doing it his way. Opinions? And I have no way of knowing if the previous repairer epoxied in the shaft tube. So what I was thinking of doing is cutting 8" off the back of the shaft tube and making it flush, then buying a new tube, cutting it 8" or so long, positioning it in place, then glassing over the whole area for the final repair.
And the shaft itself - a local wants $150 to true up the shaft. I can buy a new one online for $211 plus shipping of $20. The old shaft is ten years old. What say you.

 

[kloudie1]

New shaft and coupling.. Search on this site for MaineSail's postings on shaft-to-coupling fit and installation techniques.. Without "eyes on" I don't think I can comment on the glass/tube issue.. Once done right, ya won't have to think about it anymore.. Good luck with it.. Post pix of fix !

 

[sandpiper10471]

Send some pics of the exit tube and glass issues so we know what you are up against. Perhaps then we can contribute our collected wisdoms.

 

[tommays]

Its a pretty hard job to do correctly as its unlikely anything was ever lined up all that well

My strut for example required a .090 epoxy shim in the rear which does not sound like much but it affected the motor height by 1"

 

[letterman]

Some pics

I found out that the shaft was WAY to long without a strut. Now I am looking into either shrtening the shaft or adding a strut. If I shorten the strut, I will probably have to replace the prop with a smaller diameter one.

 

[letterman]

another shot

I am told I do not have to replace the shaft tube! I find it hard to believe.

 

[kloudie1]

The Cutless bearing has to be adequately supported inside the aft end of the tube.. and the bearing has to be precisely lined up and replaceable.. Without a new tube or splicing in a new section, it will be hard to accomplish.. If you make a long bushing that just fits over the prop shaft and just inside of the tube, then you can push that bushing up into the old part of the tube, aligning it to the shaft.. next you can slide a new tube section over the bushing which will now line up both tube parts perfectly. You will probably have to support the outboard shaft end to get this correct. The bushing should be coated with release wax before installation.. Now glass the new tube section and everything up nice,and when set, you can pull the long bushing out and the new tube will be aligned and ready for you to install the new Cutless bearing. You can see that Tommays is using a long bushing to align his tube in the hull so when it sets, it is correct. Not an easy job .. but certainly do-able.. don't forget the set screws for holding the Cutless in the newly made section

 

[tommays]

I make a lot of tools as i have to fix machines that are to big to move

I started with this one to re-cut the dammaged section

Which came out good except for the blisters

Which really ruined my day

So i made tool number 2

Which cut a nice hole through the the old hole

unfortunately the old hole was not really in the right place so i went big enough to float it in place with a epoxy mix and then use a bunch of cloth to make sure it was for keeps

I was really happy with final outcome

 

[letterman]

shaft log or prop shaft tube

The back 6 inches is reduced to half (split lengthwise) its size. The cutlass bearing goes into this with a press fit only, no screws. I am told that I can put a waxed wood or plastic tube matching the inside diameter of the remaining tube, into what is left and just glass in the back area that was destroyed. Then remove the waxed tube and insert the press fit cutlass bearing. My doubts are that the press fit will work against the mechanical bond and sooner or later I will have to do the repair again. I think the correct way would be to make a 8" fiberglass tube, cut out the bad stuff to 8", insert a waxed wood tube matching the inside dia. the length of the whole tube (so it is aligned), push in the new 8' piece, then glass in the damaged area. This way the cutlass bearing is pressing around a 360 whole tube that is chemically bonded. Yes? Any ideas besides replacing the whole tube?

 

[tommays]

I went with a piece of G10 tube because its petty perfect right out of the box and i could machine any parts to size before the bonding

I made bushings to fit between the G10 tube and a shaft for aliment during the repair as its the only way i can see it ending up correctly aligned with the motor

 

[kloudie1]

Your idea is what I was saying also.. the only problem would be cracks between the old intact tube and the hull.. If it has cracking and is separating from the hull, then it would be advisable to replace whole tube.. if no cracking and looseness, then align new 8" section and glass carefully and thoroughly. I wouldn't put the cutless in just using the fairing.. I would prefer a tube glased in..
As Tommays says if you use the shaft in addition to the wood bushing, you will have great alignment.. if you only use the bushing, then you will be aligned to the old tube but not necessarily to the engine