New Cutless Bearing

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Ammonite

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I have just ordered a new GRP shelled bearing which I was planning to cut down from 100mm to roughly 70mm as the stern tube is stepped internally. I was just wondering if there was any advantage / disadvantage in leaving the bearing longer than this. I've roughly 30mm of shaft to play with between the stern tube and the prop and it would certainly make removing it easier when it comes to replace it again. Thoughts?
 
Not sure either!

chaktoura said:
I have just ordered a new GRP shelled bearing which I was planning to cut down from 100mm to roughly 70mm as the stern tube is stepped internally. I was just wondering if there was any advantage / disadvantage in leaving the bearing longer than this. I've roughly 30mm of shaft to play with between the stern tube and the prop and it would certainly make removing it easier when it comes to replace it again. Thoughts?
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The outside 30 mm would not be supported so is there a chance that it might be prone to the GRP shell being damaged / cracking by any wip in the shaft.

J
 
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Jcorstorphine said:
The outside 30 mm would not be supported so is there a chance that it might be prone to the GRP shell being damaged / cracking by any wip in the shaft.

J
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I think the shaft would have to be very flexible for that to happen.I don't see a problem with leaving the bearing longer that the housing.I've done that on my boat that has a 25mm shaft with no problems.Correct alignment is very important though.
 
No reason not to have some sticking out. However, you need to leave 15mm or so of clear shaft before the prop to allow water out of the bearing and to allow the shaft to move forward when engaging gear.
 
Here's one of those 'no experience but what the hell' posts.. :p

If the prop picked up a rope, the rope tail would be wound round the exposed cutless shell and as it tightened, force it to rotate, possible freeing it from it's grub screws or adhesive fixing?

(I cut mine down to the housing..)

N
 
Nick - was coming round to the idea of leaving it sticking proud but I could imagine that happening. Food for thought - thanks
 
chaktoura said:
Nick - was coming round to the idea of leaving it sticking proud but I could imagine that happening. Food for thought - thanks
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If in doubt, compromise!

How about a halfway house solution, cut it so that there is only 10 mm sticking out which is enough to get a stilson on but not enought to catch or be unsuported.
 
I keep 20mm sticking out on my cutlas bearing which is the minimum required to put my pipe wrench on it and wriggle it out,

changed it 3 times now in 15 years and never had any problem with ropes twisting it.

Plank
 
I had about an inch sticking out when I replaced ours. It made no difference whatsoever and, indeed, was a small help when it came to taking it out as I was able to get a grip on that bit. Granted I ended up ripping it apart with various tools but it did all come out.

I replaced it with one with a bronze shell which also sticks out the same distance. I intend to obtain a die and cut a thread on it so that I can use a nut and some washers to get it moving. Anybody got a spare 45mm die and some nuts? Thing is with a long keel and fully enclosed prop, it is difficult to pull on the inside edge. In the past I did make a puller working through the middle but, because it could only bear on the neoprene, all it did was pull through that. That time I resorted to a professional who cut a grove in the shell with a reciprocating saw and closed the sides together to get it out.
 
All this talk of pulling makes me wonder why more people don't fit bearings on epoxy as recommended by Maritex, a thin (less than 1.0mm) film of epoxy beds the bearing and prevents it from turning but it slides in by hand and removes by cracking away. Clean up the bore with a rod slotted to take a sheet of sandpaper at one end fixed in a drill at the other. like a giant flap wheel sander.

Cutting down a bearing or having it sticking out will mean less support and ultimately more movement but on this size I don't think it would be noticeable, and as Tranoma said be aware that soft mounted drives can move as much as 18.00mm (9.00 for and 9.0 aft) and you need to ensure there is always a gap of at least 3.00mm for water to exit the bearing.
 
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