Propeller shaft woes.............

[clayjay]

Ok, just took my boat out for a shakedown after spending 11 days in the yard doing lots of maintenence which included removing the propeller shaft to replace the cutlass bearing. I am getting serious vibration from the engine and only have a usable rev range of between 1500 - 2300. Anything else and the boat tries to shake itself to pieces. The shaft seems to be true, I think the problem lies with the flange. It is a huge chunk of steel about 6 inches long and 3 1/2 inches in diameter with a flange on the end which seems to be throwing everything out of balance. It only fits on the shaft one way because of a keyway but i'm wondering if it should be bolted to its counterpart on the gearbox only one way. I saw no aligning marks on either flange when I was cleaning them so I don't think it could be that but I am at a loss.......
The engine ran fine right across the rev range before.

The only other thing I can think of is that when I removed the caked on rust from the large flange with a 60 grit 3M sanding disk I have removed it unevenly, hence throwing it out of balance. I realy am clutching at straws here and would appreciate any suggestions as to the cause.

[christyleigh]

Originally Posted by clayjay

It only fits on the shaft one way because of a keyway but i'm wondering if it should be bolted to its counterpart on the gearbox only one way.

Yes, and the 'one way' is perfectly even. That's the engine/shaft alignment you are messing with. You need a feeler guage and you need to find out how many Thousandths of an inch space between the shaft flange and tranny flange is the standard for your boat. Even if you don't know or can't find that number you must make sure that the feeler gauge (020 or whatever) slips in evenly all around the flange mating face. If your motor mounts were not disturbed in your 'maintenence' then maybe........ just getting an even reading all around may be enough.... or maybe not.

[clayjay]

Your coupling obviously looks a lot different to my one. There is a plastic spacer between the two flanges about 10 - 20mm thick that would soak up any of the gaps you would find on your feeler gauges. Thanks for trying though !

[SanderO]

Why did you have to remove the shaft to replace the cutlass bearing?

Sound like an alignment problem. Did you not re attach the shaft in the same location bolt holes?

Question for the board... I don't know much about engines etc... Why don't they use a universal joint in the coupling to eliminate the alignment problems. Wouldn't that make sense?

jef
sv shiva

[clayjay]

I'm with you on that one Jef..........a UJ seems a whole lot easier !

I could not imagine replacing a cutlass bearing without removing the shaft. As it was i needed to cut a groove down it with a hacksaw blade to collapse it in on itself, it was that tight.

As for 'Did you not re attach the shaft in the same location bolt holes?' ......well no. I figured if it was that important there would be a spigot of some sort or alignment marks at the very least........or is that too sensible ???

NOTE TO MYSELF - Stop assuming others will apply logic, always assume a ******** got there before you and you can't be disapointed.

[christyleigh]

Originally Posted by clayjay

Your coupling obviously looks a lot different to my one. There is a plastic spacer between the two flanges about 10 - 20mm thick that would soak up any of the gaps you would find on your feeler gauges. Thanks for trying though !

Well.... there has to be some way to achieve engine/shaft alignment on your boat and what I described is fairly common. For instance if you applied more ft/lbs of torque to say 2 of the 4 bolts and compressed the plastic at all or applied too little to a couple or....... anything less than perfect - you have totally mis-aligned your shaft with your engine ....... and it really sounds like you did .... because you have described the results in your original post
Of course if the cutlass bearing was very bad or mis-installed the results would be similar That's pretty much the options because there really isn't much else to go wrong.

[clayjay]

I'm guessing that is the idea behind the thick plastic spacer.........to soak up any mis alignment. I think you are right on the alignment issue though. I'm gonna break it apart tomorrow and check it out properly.

[cockeyedbob]

always a good idea to mark component alignment/orientation prior to disassembly ... punch mark, dab o' paint, etc ...

[SanderO]

When I changed my CB I used a tool which essentially threat itself into the rubber and bronze I think. It was a tube of steel which fit over the shaft and was threaded on the outside... like a piece of threaded plumbing pipe. Once I got that sucker screwed in... it was long enough to extend past the end of the shaft and had a hole to put a pipe through for leverage... like a huge threading tool.

Then I use hammer to pound it out. I was surprised at how easily this system worked. Did not remove shaft and slid new CB over and drove it home, again with a large diameter pipe which fit over the shaft.

These tools are something anyone can put together with a trip to Home Despot.

Maybe next time.

jef
sv shiva

[BarryL]

Hello,

The 'piece of plastic' you have is probably a driver saver

http://www.defender.com/product.jsp?path=-1|311|53222|314197&id=590663

Good luck,
Barry