inboard prop

[fat2nawilly]

I'm currently running a 15 1/2''d x 17p on my 23 inboard but have cavitation issues. Ive been told that i should go up in size to a 17d or 18d wheel to help prevent this issue. so my question is if i go to a bigger size wheel what should my pitch be? I have a marine power efi 350 with 315hp and a hurth 1.5-1 trans. also from the tip of my prop to the hull is 3''. any info to solve my issues will be greatly appreciated. thanks in advanced Brian

[FishStretcher]

The cheapest option to try would be to see if you can take some cup out of the prop and/ or de-pitching it. I suspect you can't pull anywhere near redline without significant slip, so you might de-pitch and keep top speed?

No slip speed for that pitch looks like 54MPH at 5000 RPM with that gear ratio. So it looks like you have room there, unless you are getting north of 45 MPH now?

That and polishing and making the leading and trailing edges more fair are where I would start. At redline, the prop tip speed is pretty high, maybe 220-230 ft/second, so you are already starting to walk a line between blade loading and tip speed.


I think a different transmission ratio with more reduction would be a better option, but prop tuning is way cheaper.

See what a good prop shop can do for reducing pitch and getting a fine edge on the prop. An inboard prop is better protected, so a slightly fairer leading edge is probably ok.

If this works, great. If not, it tells you which direction to go.

If you have the money, ACME in Big Rapids, MI makes nice inboard props.

[castalot]

Might want to call ocean props I've heard a lot of good things and they aren't that far from you
http://www.oceanpropsri.com/#2803

[Outrageous]

I purchased a SF23 inboard basket case w/o engine I think it had a 260. Prop that came with it is 16x15 for what that is worth. It seemed that a one point no expense was spared on this boat so I would think that it was dialed in with this prop.

[joshz]

My old 23 inboard had a 17 x 17 on it stock ran good with a 350 gm. Took it to get reconed and the prop shop broke a blade off. I then ran a 16x15 to try to get the rpm's up a little, I had no cav problems. A bigger prop will be closer to the tunnel and cause cav or vent problems so be careful. The 17x17 only had a inch of clearance to the tunnel. I don't think you will be able to run a 18 dia wheel on that boat, if it will fit it's going to be noisy that close to the hull or tunnel.

Lots of the cape cod 26's and albins had cav problems when turned had to port swinging a big wheel. I think they swing a 18p 4 blade might want to ask Ron Manard his take on this.

Good luck and watch that rubble pile, it f-up a few props for me.

[fat2nawilly]

Originally Posted by joshz

My old 23 inboard had a 17 x 17 on it stock ran good with a 350 gm. Took it to get reconed and the prop shop broke a blade off. I then ran a 16x15 to try to get the rpm's up a little, I had no cav problems. A bigger prop will be closer to the tunnel and cause cav or vent problems so be careful. The 17x17 only had a inch of clearance to the tunnel. I don't think you will be able to run a 18 dia wheel on that boat, if it will fit it's going to be noisy that close to the hull or tunnel.

Lots of the cape cod 26's and albins had cav problems when turned had to port swinging a big wheel. I think they swing a 18p 4 blade might want to ask Ron Manard his take on this.

Good luck and watch that rubble pile, it f-up a few props for me.

thanks for the info, i currently have a lot of noise with the prop i have now tho. I think my boat originally came with a 16 x16 or 16x17 but that one is on the bottom of Nantucket sound now so i don't know for sure but i definitely don't remember the boat cavitating nearly as bad back then. but also the shaft wasn't set up correctly then so maybe with the prop farther back had something to do with it?? my shaft at the time was about 5'' to long.

[MarkR]

nice power setup. 315HP is hefty

I had some cavitation with 260HP, 16 x 16 at 3800-4200 rpm

The solution was reduced pitch to 15 with a significant cup at the blade edges

[fat2nawilly]

OK guys i got the shaft and prop back in the boat and tested it yesterday. I went with a 17x15 with medium cup. I got 4600 max rpm out of the engine and hit 40mph wide open. I was cruising at 25mph turning 3000rpm. speed felt good and engine sounded good to. It was to calm to see if the larger prop would help with my cavitation issue but ill try again this weekend hopefully they'll be some chop out there.

[76Red18]

If you "Hope for a chop" you either own an Apache 41 or a SeaCraft...