Spun prop fixed

[petrolhead]

Well I ended up fixing my prop myself. After a few phone calls it was obvious that none of the local repairers was interested in doing it for me, I got the usual comments "What did this come off mate, the Ark?", "You can't get the parts you know", "What you need is a new prop/motor/boat/anything-else we-can-con-you-into-buying" BS.<br />So I did what I expected I'd do in the first place, moulded a new bush myself. It's moulded in 60 shure RTV polyurethane rubber, but instead of moulding the bush then pressing it in I decided to actually mould it in the prop itself, thereby saving the effort of making a mould and ensuring a perfect fit too.<br />I made a very simple wooden jig, a flat piece of ply and a length of dowel to hold the brass/bronze bush and the prop exactly concentric, plugged the holes where I didn't want the rubber to go with plasticene, poured in the rubber and inserted the metal bush. I'd done a rough calculation of the amount of rubber I'd need (volume of prop cavity minus volume of metal bush) so that I wouldn't pour in too much and have it flood everywhere. <br />I fitted the prop back on the motor while the rubber was partially cured and still compressible, so it's as good a fit as I can possibly make it, I think this is going to work OK.<br />Oh yes, before pouring the rubber I roughed up the inside of the prop and the outside of the metal bush with a Dremel, just to give the rubber something to grip on rather than the smooth metal surface.<br />Time will tell if this holds or not, if it doesn't I'll report back and let you know it doesn't work, then I guess I'll be buying a new prop but at least I can say I tried.

 

[Johnathan]

Re: Spun prop fixed

Eh Mate, you be a pretty good craftsman making that mold yourself, read your post several times figurin what you used...... duh... anyway I hope it holds up when you outrun them patrol boys!<br />John

 

[petrolhead]

Re: Spun prop fixed

Thanx John, but hardly a week goes by when I don't have to cast stuff like this in my job. The materials are to hand and don't cost me anything, and it's often the quickest way to reproduce parts, I made several new parts this way while I was restoring this engine.

 

[Thompy_04]

Re: Spun prop fixed

Sounds like some good work. Not to mention you must be a very mechanic thinker. Would also like to thank you with the help on my 18 Johny also, got her runnin' nice and smooth today. Oh and by the way, what size prop are you runnin? I believe on mine its a 9x10 and was just wondering if this is the stock prop and if I should upgrade.

 

[petrolhead]

Re: Spun prop fixed

The prop on mine is a 9.25x11, I thought that was the stock prop but maybe there were other options when the engine was purchased according to what boat it was going on, or maybe it's been changed at some time?<br />I was thinking of maybe changing mine to a 9x10 to allow the motor to rev a little higher at the slower speeds I have to do locally, I'm not sure if this would be an advantage or not.<br />The diameter and pitch should be cast on your prop hub somewhere, it was very indistinct on mine and I couldn't actually read it until I'd stripped the paint off.

 

[Thompy_04]

Re: Spun prop fixed

I really don't know what the stock prop was, but thats what mine is a 9x10. Does quite well with the set up. By the way, have you noticed that the rev limiter I guess thats what its called doesn't let the engine up to full throttle? Its just a little plate that bolts onto the armature plate basicly that lets the armature plate stop. Have you modified yours to let it open all the way? If you haven't do you think it would be ok too as long as I stayed in the recommended RPM range?

 

[G DANE]

Re: Spun prop fixed

What is 60 shure RTV ?? I have same problem on two old Chrysler propellers.

 

[Scaaty]

Re: Spun prop fixed

Everything made is made by someone, so why not make it yourself! Good show! I like thinkers and tinkerers

 

[Paul Moir]

Re: Spun prop fixed

An addition to GDane's post:<br /><br />Is this the sort of stuff?<br /><br />Mcmaster-Carr link, 'Casting Compounds' section.<br /> <br />Thanks for keeping us up-to-date!

 

[petrolhead]

Re: Spun prop fixed

What is 60 shure RTV ??

G Dane, shure (spelt "shore" in the US I note) is just a measure of hardness, 60 shure is something like the natural vulcanised rubber which the original bush was made from, maybe a little harder. RTV just stands for Room Temperature Vulcanising.<br />Yes Paul, that link is exactly the stuff, the flexible 60 shore urethane is the one I used, a different brand but it'll be the same stuff. With the one I used you get about 10 minutes pot life, demould after 24-48 hours, full hardness after 7 days, just in time for next weekend!<br />That's a very good price too, $23 for 1lb, enough to do quite a few spun props if it works. I used the same stuff to cast 4 new "bumpers", the ones that the engine shroud sits on. 3 were missing completely when I got my motor and one was split, I glued the split one and used it as a pattern to make a silicone rubber mould in which I cast the new ones from polyurethane. <br />And I totally agree with Robby, if it can be made in the first place then it can be repaired or remade, sometimes at reasonable cost, unfortunately sometimes not!

 

[petrolhead]

Re: Spun prop fixed

have you noticed that the rev limiter I guess thats what its called doesn't let the engine up to full throttle?

Mine opens all the way, when I was doing the synchro I checked by watching the carb flap as I rotated the armature plate, and it definitely opens fully. There is a stop which prevents the throttle being opened more than halfway when the motor is in neutral, is that what you mean? If so you shouldn't modify that!