I cannot tighten my prop. Every time I try to tighten it, the engine turns over. What do I do?!?!

you can hold the prop while tightening. (Use a leather glove, so it doesnt hurt.)

Even if I hold the prop, it is still turning over. Thanks.

Bring the engine up against the compression stroke, then position the prop so that it will windmill parallel to the ground if dead stick. Then slowly tighten the prop nut until the prop seats. Once the prop is seated tighten the nut down firmly. This might take a couple of tries to get the prop into the desired position wanted.

Do not screw a new prop on a quarter inch shaft. Invest in a US SAE prop reamer (about ten bucks) Ream the new prop to the quarter inch size and give the knurls on the thrust bushing a chance to do their job. This is even more important when spinners and worse poor quality plastic ones are used.

John

The problem is this: The prop is tight enough to flick as if starting, but once I apply the glo-starter, and it compresses as if to start, it pops loose.

No success, Steve.

The Nut on the shaft is not stripped?










Pulse xt 40 O.S 46ax macs tune pipe, Rapter 22 O.S 55ax, Ultimate bipe 40 evo 61nt, tiger 2 webra s40, PT-19, os 46, showtime 50 saito 82

No, it's not. I think John got it right. The prop isn't hitting the bushing, so it won't grip, thus allowing me to tighten.

Looks like you will need an additional nut for safety. All four strokes and some big two strokes have two nuts for safety purpose.
Before you go and buy an additional nut, prime your engine, enough to get harder to turn over, (Flooded engine) then install the prop and tighten the nut.

Possible conditions:

attempting to start in an overprimed condition with possibly even a hydro lock, what position is the engine mounted in?

Still not tightening nut enough. What exactly are you using a spinner nut, regular nut or a spinner of some sort?

Agine did you ream the shaft hole or does it go on tight over the threads? If you force it over past the shafts thread shoulder then this causes an inability to tighten the prop enough. You cannot use the nut to try and force it all the way up to the thrust bushing knurls.

You won't be able to get an objective answer untill you come up with some answers.

John

yetti831,
Cut a disk in fine sandpaper the same size as your drive bushing. Place this between the drive bushing and the prop, or the drive pushing and the spinner backplate if you are using a spinner.

Ken

Yetti,

I understand what your saying it happened today to my son. He was putting an old OS 40 back into service on an airboat he is building using a dome type prop nut that is tighted by inserting a pin as a wrench. Upon starting it backfired loosening the nut.

When we say tighten the nut firmly, it needs to be very tight. Otherwise you risk the danger of throwing a prop either on the ground or inflight which happened to me some years ago. Compressing the prop to some degree is normal. As mentioned above once the prop seats, I hold it with the non wrench hand close to the hub and torque it down to where the nut stops not over forcing it beyond tight.

Hope that helps!

Steve

Problem solved!!! The backplate of my spinner was not hitting the bushing. So, I took a pair of scissors and placed a blade down the backplate's center and turned it, just as if reaming a prop. This widened the center and allowed the backplate to hit the bushing. I was able to tighten it. Thanks for everyone's help!

I'll bet you are running a low pitch prop. Several of my engines require a spinner back plate for those props or the nut bottoms on the threads before the prop tightens well. The other likely cause is that you don't have a propper front washer and again you are running out of threads. The front washer should be quite thick with a taper on the front surface.

I run into this with the 3 3/4 and 4 pitched props. If I don't have a spinner back plate they won't tighten even enough to turn the engine over. The 6 pitch is usually OK and a corser pitch is always OK.

Don