EF

Concerning locking the prop nut on a four stroke engine, I’m well familiar with the nut and lock nut system supplied with the engine, but was wondering is it ok to use two regular nuts and simply tighten the first against the prop washer and tighten the second against the first?
Will it be just as safe in case the engine backfires?
I was given a s/h Saito 150 that’s missing the prop nuts (I do have the prop washer) and it’s a bit difficult for me to locate the original parts (out of stock in many places) not to mention extremely expensive when I include shipping costs…

1200SportsterRider

On that big block Saito I would stick with the original nuts or similar like this. I'll dig up more choices.
https://www.truturn.com/?year_id=381...vpf-ymm-search

These are for the 125-a and are 8mm x 1.25 thread, same as the 150:
https://www.towerhobbies.com/product...AI125A135.html

jaka54

Hi!
During my 45 year in this hobby I have never used anything more than a single prop nut on any glow engine, two or four stroke! And have never had a prop come lose!

EF

You are lucky I guess.

In 40 years of flying I’ve had two occasions in which a four stroke engine backfired.
First with a .61FS, during flight, then with a .70FS just before takeoff.
In both cases I had the manufacturer’s nut and lock nut installed and in both cases this kept the prop secure on the shaft, freewheeling, while the engine stopped.
So, from the safety aspect, using a single nut on a FS engine is not an option for me.
The only question is whether two identical nuts would provide the same service…

daveopam

My Feedback: (9)

I used a Higley prop nut with matching lock nut for years on a saito 1.25. Had zero issues. I know backfires can and do happen. But for me it was a rare.

David