On my 12'' to the foot Dutch barge the stern tube is filled with gear oil. There is a conventional inboard stuffing gland and a face seal between outer bearing and thrust face of the propeller.
So far so conventional, however instead of pumping top up oil with a large grease gun there is a pipe connecting the tube to a small oil reservoir placed above the shaft just at static water level.
This arrangement works really well, no seepage of oil or water when moored up and only a small trace of oil at the water surface when I have to use a touch of reverse to stop her.

This system would work well on a model boat using very thin oil. Oh yes, I restored a 1936 outboard motor and lost the prop because I forgot to replace the split pin on the retaining nut!

Fair winds and smooth seas to you all Captain Lemmerhengst

HI George

Ref several post about losing props. I use a drop of stread lock on my props, just a drop and make sure it is the semI hard releasing type, not premanent.!!!! if you need to remove the prop for any reason, you can.

Mark

PS. I have used both oil and grease in the prop shaft and prefer oil, in cold weather the grease thickens up and causes drag on the shaft, the problem with oil is the need to keep topping it up, have a shaft tube with an oil tube fitted makes this easy.

Dave that's brill thanks for all your help can't wait to get this boat on the water thanks agin
Regards
George

HI George
I am attaching an exploded view of a prop shaft with the prop, locknut and washer plus the bearing which will fit in my prop tube. This is for demo purpose only as the nut and washer are not brass, but hopefully it gives you how it all fits together.
Cheers
dave

HI Dave
Could you explain more about the thrust washer maybe a picture not to sure if I have this on my boat maybe a picture of whole thing Ie prop, nut, sharft bearing, washer and prop shaft any help is appreciated I cant wait to get this running right so I can enjoy this boat.

Regards
George

HI George
Yes you do need to lock the prop to the shaft with the lock nut. I have made special thin spanners to hold the nut so I can adjust in situ. You also need a thrust washer between the nut and the shaft bearing, preferably brass. The play between the washer and the bearing is minimal, at one time we used to use a cigarette paper like a feeler gauge but unless you are running at high revs you can set this by eye and feel. As long as there are no tight spots you should be OK.
At the other end of the prop shaft you should have another washer and nut again locked to the drive joint. This will protect the bearings in your motor as they are not designed to take longitudinal force.
Failure to lock the connections will either result in the prop or drive becoming detached or the drive and shaft seizing resulting in damage to the motor or ESC. For this reason you should also have a fuse fitted between the battery and ESC rated at less than the mtor stall current or the max amps for the ESC, whichever is the lower.
Hope this helps
Dave

This post is very useful. I have the same problem with my solent Lifeboat I lose my prop on the first outing with my boat so all I have to do is threat the prop on and the nut that is on the shaft then has to tighten against the prop is this correct.

Regards
George

Ignore my gibberings as I was looking at the wrong references (Note to self, do not do complicated 'finkin' after a long drive 😯 ) and can see an easier method that does not involve exposed shafts and very conical housings. I appreciate your assistance and will retain tips etc for future projects.

I am also not very good at loading messages, do not press submit reply more than once.

I agree with pmdevlin with reference to the use of oil as a lubricant in prop shafts. I thought I knew it all on my fire boat and initially used grease, but I did some experiments as described in my blog " fireboat c of g " and was very surprised at the difference.

As to locking the prop and coupling to the shaft this requires some care. On my fireboat I have had both the prop falling off and the coupling coming loose in the middle of the lake requiring the help of a fisherman and hiring a row boat to recover the stranded craft.

I am not really too sure what you mean by conical housings around the shafts, perhaps a sketch might help?

The small amount of play you need is along the length of the shaft. The clearance between the diameter of the shaft and diameter of the bearing bushes has to be as small as possible but still allow the shaft to rotate freely without the shaft vibrating and rattling around.

My plan for HMS Rupert is to have the last 50mm of the shafts sheathed within conical housings that extend out from the hull and have the props at the end.

I intend to make these from thinner brass tube with an inner dia allowing free rotation of the shafts and a narrower outer end to the housings. Your information suggests that while the nuts have to be quite snug to the end of the tubes they must allow a small amount of play. I hope this doesn't sound like a plan for failure!

grease, or oil, a debate that has been going on for years. My take, all my boats use oil, here is why. (IMO!!)

when the prop is spinning, the grease funnels, so provides very little lubrication. Over time it will go off due to water ingress and heat, you then have to clean it out. if your shaft bearings are good, virtually no water will go up the shaft. Most supplied shafts have acetate bearings (black plastic push in) and are pennies to replace. These are water lubricated, so don't run the motor with shaft connected for very long out of the water. With oil, via a oiler tube soft soldered on to the shaft, every time you run the boat its easy to put a few drops into the shaft. The Oil almost clings to the shaft, and prevents a possible surface rust (stainless shafts don't actually rust) during periods of not being used, and lubricates, like I say, its preference.

With the nuts, you need a very small degree of endfloat. The prop end, back the nut all the way tight onto the thread. I silver solder mine so they don't move, but if real tight should be ok. inside the boat, lock the nut up to the universal joint, and slide the uj on the motor shaft to create the end float. You need to get the motor and shaft lined up properly to avoid loss of power and excessive amp draw. if you can, make a sleeve so they are lined up as a solid unit.

Hope that helps 👍

Regarding play along the shaft.

You need to have a washer between the nut and shaft bush at each end. Then lock up one end (nut onto coupling or prop, depending on which end you start with). Next lock up the other end so that you can just feel a little movement as you push/pull the shaft. it only needs to be a little movement, say 1/2 mm or less. This will prevent the shaft from locking up against the tube when in use.

Next, the coupling. You need to secure the coupling bushes onto the shaft and motor in such a way as to allow about 1 mm movement of the flexI part of the coupling on the bushes. The reason for this is that as a motor changes direction from clockwise to antI clockwise rotation there is a v small amount of movement axially within the motor.

Ian

Thanks David makes tomorrow a lot easier. it's install day !

Thanks for the info

I put grease inside the prop shaft and this stops water entering the boat I use a very thin type of grease what car wheel bearings use. the nuts on each end should lock Ie when you tighten the prop they lock together with the propeller and nut, the same on the other end to coupling, but not sure if flexI couplings are threaded if not has it got grub screw on it. others will say don't use grease, but I have never had any problems 🕊

david