I picked a new APC 10x6 out of my stock and tried to slip it on my Saito 45. It went over the threads OK, but not over the sholder. I put my reamer on it and it took quite a cut to get to 1/4". So, the engine isn't the isue, but the props may be tight and need reaming to 1/4"

There are a few things I would like to point out about reaming the props, and I'll focus on the APC props. As I pointed out above, they may run tight in the bore. This is good because I would rather have a prop that I could ream to size vs one that I had to use bushings on.

The prop reamer is a "Hand Reamer", with stepped sizes. If you chuck this reamer in the drill press and poke it through a prop, a couple things may happen if your drill press chuck isn't running very true, the table is not trammed to the chuck spindle, and you don't have a good fixture setup to keep the drive surface of the prop aligned correctly, your reamed prop may have an over sized hole, and one that doesn't track to the orginal bore. By reaming by hand, and from the right direction on the prop, the piilot on the reamer will keep the reamer running true to the orginal bore.

When reaming the prop, never back up the reamer. The fit to the reamed hole is zero clearance and if you back up the reamer, you stand a very good chance of picking up some swarf and locking the reamer in the prop. Also backing a reamer up destroys the cutting edge. Remember, these props are glass reinforced plastic, so they are quite abrasive to tool steel.

The APC props are cast with a larger bore at the back of the prop than the bore in to front. To get things going straight, start the reamer from the back. This gives the longest guidance for the pilot, all the way to the point the next step penetrates the front surface.

After you ream the prop to the size, contiue turning the reamer in until you get a slight chamfer from the next step. THis cleans any flashing on the hole and allows the cones of the prob blancer to fit accuratly to the bore. When you remove the reamer, continue to turn it clockwise, not backing it up. Now feed it in from the front and again cut a slight chamfer where the reamer exited the face of the prop. There will be a lot of flashing here and you need a good clean base for your balancer to work from.

I took some photos of the reamer in action poking a 5/16" hole through a prop that was fit for a 1/4" shaft ogrinally. Note the broken end[>:]

Sorry about a couple of photos not focused well, but I think you will get the idea

Don