I have a 1.20 O.S. Surpass w/ 16-8 master prop on a GP Giles 202. Just how tight should the prop nut be? I have cranked on the %#@#% thing and the prop still moves over against my spinner. Am I tigtening it too much maybe? Is there a better prop pitch that I can try for more speed?

Or...is the spinner moving against the prop? What type of spinner are you using? I have had this problem with my GP aluminum spinner not being tight enough on the adapter nut, thus allowing the spinner cone to rotate to the prop. Just a thought

I'm using a 4" Dave Brown P-51 parabolic spinner. Should I still use the lock nut that came with the engine along with the adapter that came with the spinner?

I can't quite picture that specific adapter in my head but if they will all fit on the crankshaft, then give it a shot and then do some ground run-up tests.

I'll check the spinner bolt that holds on the cone. Good Idea, I didn't think of that.
Thanks

The nut is probably bottoming out before you get enough pressure on the prop to hold it. I picture that you have a smaller screw that holds the spinner onto the nut/adapter. If you are lucky a spacer or washer behind the nut will take up the slack, hold the prop, and still allow the spinner to fit tight onto the back plate. If not you might need a spacer between the thrust washer and back plate to get it tight.

rod

That's the problem I had. I solved it by getting a Dave Brown Long adapter instead of the short one. This gave the bolt more bite and allowed it to seat fully on the spinner cone.

Don't add a washer between the thrust washer and the prop. Two washers together can act as bearings and make slipping easier.

Try a donut shaped piece of sandpaper between the thrust plate and the spinner and/or one between the spinner and prop.

And DEFINITLY use both nuts that came with the engine. The second locks the first in place.