Headed out for test run

captainmaniac · Post by **captainmaniac** » Tue Mar 09, 2010 10:46 pm

If you only got 3000 RPM at WOT its either a major prop oversize issue, or possibly a tuning issue as well... Ignoring prop diamater, for every inch of pitch you would typically see a difference of about 200-300 RPM. You should be around 4200-4500 RPM at WOT, so if you have the right diameter you are about 4" over pitched. I can't remember the formula / relationship between diameter changes vs rpm.
Its kinda fuzzy, but I seem to think my father's old 28' Sea Skiff (1969 model) had a 12x12 prop (the boat's been gone for 10 years so I'm not sure anymore).
If you can't bring RPMs in to the right range with a prop change, look for timing, compression, coil, no spark on a cylinder, tired engine, etc... for the extra oomph.

rossjo · Post by **rossjo** » Wed Mar 10, 2010 12:00 am

Wheres the videos?

foofer b · Post by **foofer b** » Wed Mar 10, 2010 7:19 am

Again, too much prop. The F26 came standard with a 14x10.

Rodman · Post by **Rodman** » Sat Mar 13, 2010 12:40 am

Went to Roy`s house. Picked up his spare prop. I will try it this weekend see how it does. 14x12

foofer b · Post by **foofer b** » Sat Mar 13, 2010 7:41 am

Is the hub much shorter?? How much space between the strut and the hub?

prowlersfish · Post by **prowlersfish** » Sat Mar 13, 2010 10:25 am

the hub should be fine , You will need a new key way the one that was used with the old prop is a stepped type due to the adapter use on the larger prop . The 14x12 is still to large but will be a lot closer then what you have.

Rodman · Post by **Rodman** » Sat Mar 13, 2010 10:29 am

I will go get a key this morning what kind of key should I ask for?

prowlersfish · Post by **prowlersfish** » Sat Mar 13, 2010 10:37 am

Brass square key not sure of the size but it should fit snug in the prop . ( take the prop with you) better a liltle too short then too long .

Rodman · Post by **Rodman** » Sat Mar 13, 2010 10:59 am

Thanks

prowlersfish · Post by **prowlersfish** » Sat Mar 13, 2010 11:21 am

Heres more info for you the only thing I disagree on is I think the liltle nut is first .

http://sbmar.com/main/articles/propelle ... ittle_nut/

wowzer52 · Post by **wowzer52** » Sun Mar 14, 2010 10:47 am

Prowlerfish is right, the little nut goes on first. Who's on second?

Rodman · Post by **Rodman** » Sun Mar 14, 2010 4:04 pm

I went out today with that new 14x12 prop I got from Roy ( FooterB), I could not get the boat to even plain out. So I am at a lost now. The rpms did go up to 3500 rpms, But It will not plain now. Any ideals?

MattSC · Post by **MattSC** » Sun Mar 14, 2010 5:04 pm

You are going in the right direction. Based on your rpms, I would either try a 14 x 10 or 14 x 9 with a full cup. I've tried my F-26 without a cupped propeller and it couldn't get up on top, the prop was slipping, even though I reached my recommended rpm. I took a degree of pitch out and added a full cup and I couldn't believe the difference. Night and day. I think you might be shy of 4000rpm if you try the 14 x 10 cupped. I'd try the 14 x 9 cupped if it were me.

alexander38 · Post by **alexander38** » Sun Mar 14, 2010 7:39 pm

hey, Rod you need the right prop and your bottom needs work sanded and paint you believe the difference it makes. I found out the after a cleaning and paint job I got 5 knots of speed, and I'm going to take my wheels from 22 x 22 to 22 x 21 and mild cup to get more mid range bite. But get the right wheel and start from there. And are you sure your planes are holding and not leaking down on you ? are they clean ?

wowzer52 · Post by **wowzer52** » Sun Mar 14, 2010 8:06 pm

I think I mentioned that my F-32 wouldn't plane until I redid the bottom. Big difference.