prop bolts 3/8 or 7/16. does it matter?

[pilot2512]

I got a used engine that has 7/16 prop bolts. I'm planning on a Catto prop. I know the nuts can be changed out, but are there any advantages to moving up to 3/8"?

[Ron RV8]

3/8 is smaller than 7/16... Or did you mean it the other way?

[terry.mortimore]

Hi Jay, check your tape measure. 7/16" bolts are larger than 3/8".

I have the smaller 3/8" bolts and I'm wondering if they will be suitable. I"ll be using a 4 inch extension with a ground adjustable Sennsenich prop. I haven't asked the question yet, but it's getting close.

If you still want the 3/8" I'll trade ya


Terry

[LifeofReiley]

Originally Posted by pilot2512

I got a used engine that has 7/16 prop bolts. I'm planning on a Catto prop. I know the nuts can be changed out, but are there any advantages to moving up to 3/8"?

you will want to stay with the larger 7/16" bolts for many reasons.

[AX-O]

at the end of the day it does not matter (as long as the horse power has not been dramatically upgraded). You will need a prop extension. Get it from Saber.

One side of the prop extension will have the engine bolts, the other side will have the prop bolts.

I have a 320 with 3/8 on the engine and 7/16 on the prop, I have a 7/16 on the engine and 7/16 on the prop. I just ordered one with 1/2 on the engine side and 7/16 on the prop side.

Keep what you got.

Edit: posted at the same time as Reiley.

[pilot2512]

Yes, 3/8 is smaller than 7/16. First cup of coffee not in affect when I started the thread. Lol. Thanks for the replies

[smokyray]

Originally Posted by pilot2512

Yes, 3/8 is smaller than 7/16. First cup of coffee not in affect when I started the thread. Lol. Thanks for the replies

Jay,
If you bolt on a wood prop, the 7/16" bolts hold torque easily to 25 hours, the 3/8" not so much. When I built my 4 it had a Sterba woodie and 3/8" bolts. I checked my prop nuts every 10 hours, more often than not they weren't up to 22ft lbs. After switching to 7/16" bolts, the problem went away. 0-360"s use 7/16" bolts (or 1/2), size does matter!

Since Craig's props don't "swell" like wood props, 3/8" prop bolts for an 0-320 would be ok. However, the first Catto RV prop was on my 0-320 powered RV4 with 7/16" bolts!
I know what I would do...

V/R
Smokey

[LifeofReiley]

Originally Posted by smokyray

0-360"s use 7/16" bolts, size does matter!

SmokyRay... I'm pretty sure 360's use 1/2" bolts. Well, at least all the ones I've seen have used 1/2" bolts.

[smokyray]

Originally Posted by LifeofReiley

SmokyRay... I'm pretty sure 360's use 1/2" bolts. We, at least all the ones I've seen have used 1/2" bolts.

Reiley,
You are correct sir, the 0-360 flange bolts are 1/2". However, many FP RV cowlings require an extension which attaches to the flange with 1/2" bolts and 7/16" or 1/2" through the prop. Craig Catto's and many other prop makers allow both options.
I opted for the 1/2" flange/Saber extension bolts, 7/16" prop bolts on my RVX 0-360J2A
V/R
Smokey