transferring the drive from the shaft to the boat

Hi All,
I have recently bought a 42 ft steel hull yacht. have repowered it and it is back in the water. Was manouvering around the mooring the other day and put it in reverse and applied a bit more power than have before and suddenly was loud clanking and then no drive. upon investigating found that the prop shaft had pulled sternwards enough for the drive plate to fall off. The boat is coming out of the water in 2 days to get this sorted. just wondering what systems are used to transfer the drive from the shaft to the boat.
here are some pics showing the present setup. basically the shaft comes out of the stern tube and has a rectangular keyway which a drive plate fits on then a short shaft with a universal at each end then a adapter plate then the gearbox. the short shaft with universals on each end can slide short or longer so the the transfer of drive must be before that. The stern tube has a plate on the front with bolts around it, this holds and oil seal and i took this off there is a bearing behind it as in the other picture. is this bearing a thrust bearing where the drive is transferred?? If it is it is not working as the shaft slides in and out of the bearing.
Any help in fixing this would be much appreciated.
should the drive be transferred to the boat with a thrust bearing setup or through the gearbox /engine/ mounts???

cheers

 

goodness
usually the shaft has a half coupling, the half coupling is fixed to the shaft by one of several methods, a clamping arrangement which is very good and involves no machining, or a taper and nut, with key, very expensive machining, if the Gear can take thrust then there need be no thrust block
if the mts are flexible it is usual to have flexible coupling OR clock dial the shaft half coupling around the gear half coupling, to align
on no account should the shaft be pulling on any drive plate, perhaps you may explain a bit more and picture the gear
cheers

 

sketch of current setup

here is a sketchy sketch of what is there at present. when we repowered the boat. just installed new engine and gearbox didn't go further back than that. just figured it was ok.
with this system the transfer of drive has to be in the stern tube some sort of thrust bearing setup. what do I need to change. install to fix it properly.
thanks

 

oh!! I see, that is a coupling not a drive plate, the drive plate is at rear flywheel
ok, counterbore the coupling,, if you cant counterbore enough you must machine a deeper coupling , thread the shaft, enough take to thinnish nuts, one to lock other, or try cheapo way put two large grub screws into coupling and drill shaft sides, screws abt 120 degrees from each other, you only need dimple shaft, say 3/8 hex drive screws, it will work
or taper shaft, taper, coupling, thread shaft end and nut to suit rotation
wot has happened is going astern the clip has left its groove, all looks bit Bodgy, (bodgy nz saying

 

more

Hi,
cheers woosh for your help.
sorry for mislabelling the coupling
I got the engineers today to put grub screws in the coupling and I am going to drill the shaft. I figured this would be temporary just to give me power to get to the haulout. as the universal joint/cv shaft slides in and out when the coupling is fixed to the shaft ,in reverse it will get pulled back until the coupling hits the sterntube. So i suppose I am going to have to install some sort of thrust bearing between the stern tube and the coupling plate to transfer the drive and stop the shaft from sliding forwards and backwards???

 

you would be astonished at the power of two screws, I would do that, and nothing else, I would tie the boat with springs to dock and run her fore and astern, dont ferget to give me some points and say hello to Ak, lived there a long time once

 

points??

Hey Woosh,
how do I give you points??
Auckland is ok. you prob glad you got out. its madder than it used to be. the traffic is shocking now haha. getting nearly like LA. if you want to go anywhere then you better drive late at night. ..not quite that bad yet.

Still one problem with the grub screw setup. the shaft can still move forwards and aft cause of the movement/play in the cv shaft and the coupling will hit the stern tube when in reverse. if I lock the cv shaft the drive is then transferred to the engine and mounts which are flexible. Is this ok?

thanks again

 

if the gear will take thrust(what is it) then ok, to make thrust bearing is not easy, Whiting power systems has the stuff, but is expensive although I always used it, thrust and cv all in one
to post feed lookat top of box says post feedback or something
this is best
http://www.aquadriveusa.com/system/system.htm

 

it is all connected through to a borg warner 72c 2.9-1 reduction box and a nissan td 27 75hp diesel. mounted with bolt on rubber and steel engine mounts. not sure on the brand or name of them.

 

Re transferring drive to the boat
From the drawing you supplied and photos ,the bearing shown is the thrust bearing ,it would transfer thrust to the stern tube , a bit unorthodox but you never know with boats. with the sliding double universal joint ,that cannot transmit thrust so thats out.
now back to the bearing ,for that bearing to transmit thrust it would have to be one of two types 1 thrust bearing with integral locking ring. 2 thrust bearing with tapered bore and adapter sleeve ,both these systems were used extensively years ago....but....i can see no evidence of locking ring or adapter sleeve ,are you sure the bearing has not been replaced with incorrect type ,something is missing ,just my 2 cents.
cheers hartley

 

Hi there,
my thoughts exaxtly. the bearing is just a standard one.I 'm not sure how it even was working before. There definately is a thrust bearing missing from the setup. there was'nt ever one there.Been talking to a few bearing companies and have 2 options. one pull out the original normal bearing and replace it with a thrust bearing with tapered sleeve and locking nut, or 2 add another bearing in a separate housing between the stern tube and the coupling plate and bolt it to some of the holes on the stern tube. haven't got much room to move so have started taking out the existing bearing but as usual am having trouble getting it out.
oh well never mind It should get sorted tomorrow. might have to machine the plate with the oil seals in it to accomodate the new bearing but should be straight forwards.

thanks for your help

 

Bigbear
Looks like you are on the right track ...good luck
cheers hartley