Prop size difference LH vs RH

[Todd320]

On my 320, I had a ding in one prop, so had them both reconditioned (hired someone to remove, take to prop shop, then reinstall). He asked the question why they were different sizes (18x18.5 and 18x19). I believe he works on mostly larger boats, typically he dives. I have no idea, that’s just what the manual stated. I spot checked other boats by pulling up the Sea Ray manuals, and sure enough, 08 48 DA, identical LH/RH sizes, same for a 38 diesel, but the gas version v-drive used different sizes.

My guess is on the gas, the higher RPMs exaggerate the difference in gear ratios between running one transmission in Forward, compared to Reverse, so this slight adjustment in pitch compensates for that? I noticed on one Hurth spec page, they mentioned slightly different ratios for position A vs B.

320:

48 Sundancer: identical 24x29

38 Sundancer (all were 08 manuals), gas options used 21x22.5RH and 21x23LH, diesel, identical 21x24

 

[Todd320]

They came out really nice by the way, but have not sea trialed them yet...

 

[markrsimon]

Those look sharp. What coating/paint is that? Been trying to figure out if I should paint mine or not.

 

[Todd320]

Those look sharp. What coating/paint is that? Been trying to figure out if I should paint mine or not.

I have no idea, he mentioned something about a special concoction that prevents marine growth for a year, not propspeed. Not really needed since I store the boat out of the water, but looks good. Do you want me to ask him?

 

[markrsimon]

If you run into him, and its an easy ask - it would be appreciated. I was looking at Velox as a DIY option - but havent heard anything good about it, just a few bad comments here and there.

 

[Strecker25]

I believe you’re spot on as to why the props are slightly different. I’ve read others mention the same thing on 320/340s of your vintage where one side is slightly less pitch.

 

[Todd320]

If you run into him, and its an easy ask - it would be appreciated. I was looking at Velox as a DIY option - but havent heard anything good about it, just a few bad comments here and there.

He said it is a special mix he uses. He is willing to talk to you if you want me to give him your number, message me if you are interested.