rcflyerjoe123

What is the best way to mount a new propellor on a 4-stroke engine? The prop threads onto the shaft but of course, the shaft turns. I have been warned not to hold the shaft or flange with a tool as it can crimp the shaft. If I ream out the prop, how much do I ream? I have not had this problem on my 2 strokes, I guess the shaft size is different on the 4 stroke and is a tight fit on this prop.

davidmor

You need to ream the prop. Pick up a prop reamer at your LHS. You will need to get used to doing this as just about every engine out there bigger than a .46 has a prop shaft bigger than the standard prop hole. And to make it even more fun, different manufacturers use different sized shafts from each other for the same sized engine! I personally use a drill press and a stepped bit (unibit) to get it just a shade smaller than the prop shaft. Then I run a straight bit through to finish it up. It keeps the hole dead centered doing this way. Nothing like ruining a $30 prop by an off center hole to make your day![:@]

Scar

My Feedback: (3)

Davidmor is correct, but I have a question for you. Did you "thread" your props onto your twostroke? I saw this, once, and the guy actually ran his ST 40 that way. He had a nut on it, but it couldn't apply proper clamping force on the prop, because the prop was hanging up on the prop threads. When I saw him, he was trying to start it with an electric starter, which would just spin the prop off, spinner and all. I got my reamer out of my box, took care of that, and he could start the engine with his electric starter.

If you were "threading" your prop onto your twostroke engine, you would be well advised to ream it, too. Then the prop nut can apply force to the backplate through the prop body, rather than applying that force to the first couple of threads.

Good luck,
Dave Olson

upnflyin

You didn't say what kind of 4 stroker you had but its probably metric so you will need a metric prop reamer of the same size. Check into it further......
Al

MinnFlyer

My Feedback: (4)

If the prop will thread onto the shaft, chances are it will go all the way on. If I have this happen, I just hold the thrust plate with a pair of pliers and spin the prop all the way down (Yes, this will put some little gouges in the thrust plate, but frankly, I don't care). If the prop won't screw all the way down, THEN I will resort to reaming it.

aimmaintenance

Ditto.

Geistware

My Feedback: (16)

On glow engines, I normally mount the propeller so that when I rotate it backwards I come up on the compression stroke at 3 oclock. This way with a dead stick, the propeller settles horizontal. Seems to work OK. When I flew glow, I never broke a propeller unless I crashed.

DBCherry

My Feedback: (4)

Ditto ditto.
Dennis-