Poulsbo Panza 's 10" prop.

[Walcheren]

Well, I did get a 10"propeller, L,10x8, for 5/8th shaft. Bronze. Looks gorgeous. Should hang it in my living room. The fellow that sold it to me said he had it on consignment for 5 years, put in two bronze set "bolts" and that these props are not made anymore except by special order. Cost $75 Cnd. Not bad I thought. My good friend in Nova Scotia suggested a pitch of 10". However, although I could have had the pitch changed, I thought we leave it well alone for now and see what happens. Well, first sea trial. The engine was really working now, sounded good. Speed up to 6 kn.i.s.o. 4, a real prop wash, a nice wake and lots of water climbing up the bow. However, after half an hour and a rest I had to negotiate a large area of drift wood so used reverse quite a bit as well. She goes backwards also perfectly! But after another few minutes and 4 miles away from home I lost power. Engine was running fine, shaft was turning around but the prop was not. So the bronze set bolts must have failed. So I rowed to the next island, set on a rocky ledge a foot in the water and with my chin over the transom, by feel, with my 3/8 wrench I "reset" the set bolts trying to find the two flat areas filed in the shaft. Off I went. O.K. for 3 minutes and the same thing again. So back to shore and same procedure. In the meantime I pick up masses of seaweed which at one point I blamed for all my troubles. Same result. I repeated this activity four times after which I decided to let the engine idle thereby reducing torque and sure enough an hour and a half later I got back the the launching ramp. Result. Stainless steel setscrews plus lots of locktight. They work fine. Next problem. I use a coupling with a plastic insert to connect the transmission and the propeller shaft. When the propeller is driving the boat the coupling is driven trogether. However, when going into reverse the prop wants to pull the coupling apart. So I insalled a "clampring" around the shaft with three bronze washers between the stuffing box and the ring, the washers functionong as a "bearring". This looked good and worked well with the smaller prop. The ten inch prop however pulled the boat backwards hard enough to make my clampring slide over the shaft and in the process uncoupling my connection to the transmissionm. No power. So now I have also in this ring a setscrew set on a forward slanting area filed on the shaft. I thought some of you might weant to know about these pitfalls and adventures. Fortunately the sea here is not that cold so you can sit in it while fixing your boat. Dirk

[Nicholas Carey]

Originally posted by Walcheren:
[tale of propellor woe and intrique elided]Get thee to a decent propellor shop.

Propellors are normally attached with a woodruff key, not setscrews.

There should be a slot milled in the inside of the shaft hole in the prop..maybe 3/16 in wide and about the same deep. In the end the shaft, there should be a matching slot milled.

A key—a tapered, machined rectangle of metal sized to fit the keyways is fitted there to prevent the propellor from slipping and lock it in place. The shaft itself is tapered, as is the hole in the propellor that receives the shaft. Once seated and the keyways aligned, the woodruff key is driven in to lock the whole assembly together.

[Walcheren]

YES, but. We need to accept the propeller I have. Has worked for ages and should work again. The hole as not tapered. The key you suggest has gone through our minds. Question is where is the weakest link going to be in case we strike drift wood or worse, a rock. At the prop or is it at the coupling with the plastic insert or do we have to accept 0 weak link with all the unknown consequences of same. I like the key idea myself. It would only take the removal of the shaft and bringing it over to my machienist friend two blocks away. I thought I try the set screws first. That is how the propeller worked in its previous life. I suppose I could get a new shaft, 3/4 , have the prop tapered from 5/8 to 3/4 etc. and put a woodruff key in. Gets expensive if possible to do and is it necessary? There are lots of prop shops around. Thank you for your interest and suggestions. Boatbuilding has a long learning curve. Dirk.

[Brook Hamilton]

Dirk:

It is fun to read about your adventures. The standard has evolved into the tapered shaft and key, but I hope you can get what you have to work. "Messing about in boats" includes some experimentation and it adds to the adventure. The 12x12 bronze prop I told you about is set up for a 7/8" shaft and a shear pin, like on an old outboard. So lots of things can work. (However, changing a shear pin on an inboard out in the middle of the chuck after hitting a piece of driftwood would make for an interesting tale). My 12x12 may stay where it is - on the basement wall.

You may want to try 2 short set-screws per threaded hole onto the flats of your shaft. The second one serves to lock in the first. It may depend upon how thick your hub is. Good luck. Brook

[mmd]

Glad to hear the performance improved with the new prop. Once the "lock-in-place" problem is solved, you should be all set. I think that set screws will always cause you grief and will chew up the shaft badly over time. Keyed props are better in almost all applications. One is indeed lucky when one has a friend who is a machinist! ;)

[Walcheren]

Yes, having a machienist next door, almost, is a blessing and I told him so. In fact after my adventure last week and before going home, I went along his shop and we fixed the situation right there on the road with stainless set screws. Bottle of wine is O.K. I get the point of chewing up drive shafts but again that is not that big a deal. 4 or 5 feet of 3/4 SS shaft does not cost an arm and a leg. Now, the question for me remains, should there be a weak link in the drive system or do I just forget about it and if I hit that log or rock and bust the deadwood and/or shaft log, I'll just have to deal with that. I did consider 2 1/4" set screws in each hole. Presently I have 3/8 plus lock tight, not enough room left for another one. I did try that. Does the engine quit before anything happens? I did deal with a 26 foot cruiser that hit a piece of drift wood and I know what happened to that one. I was not on board! Also the visibility from my little craft is a lot better than from the cockpit of a cruiser and I am only going 6 knots not 14. So, final question:" Weak link or not".

[Brook Hamilton]

I'm curious to see what folks say. From what I have read is there typically is no "weak link" in an inboard drive. However, if you could have a shear pin, or some sort of slip coupling in the boat where you could see it and deal with it, that may be a good way to go. I'm not sure you want to have to get into the water to keep tightening set screws though since you can't be sure they will stay locked in place. Brook