Prop Slip

[Dcmphee]

Hey everyone, I am wondering what the normal prop slip numbers should be for my boat. I have a Rinker 232, with a 5.7 alpha 1 Gen 2 combo. My slip numbers at cruise are around 13 percent, but at WOT I seem to climb to 18 percent. Is that normal? My best WOT run was 43 MPH trimmed, @4800 RPM with a 19 P 4 blade prop. I know my boat is pretty heavy for a 5.7, but wondering if that is what I should be expecting performance wise. Thanks for reading!

 

[Dcmphee]

Maybe I should have posted this in the prop section? Mods feel free to move it if that is correct.

 

[porscheguy]

1.62 ratio? In general slip should decrease as speed increases.

 

[Dcmphee]

Yes, the ratio is 1.65 or 1.62. I think because the boat is 4200 pounds dry and was originally just a 2 barrel carb.

 

[dingbat]

Hey everyone, I am wondering what the normal prop slip numbers should be for my boat. I have a Rinker 232, with a 5.7 alpha 1 Gen 2 combo. My slip numbers at cruise are around 13 percent, but at WOT I seem to climb to 18 percent. Is that normal? My best WOT run was 43 MPH trimmed, @4800 RPM with a 19 P 4 blade prop. I know my boat is pretty heavy for a 5.7, but wondering if that is what I should be expecting performance wise. Thanks for reading!

I was running a 14.25 x 17, 4 blade with 18% slip as well. Dropped to a 15 x 15, 3 blade and cut my slip by 50%.

Caveat....i was a couple hundred rpm low on my WOT. The drop in pitch bumped my WOT rpm up and the change in prop design cut the slip in half. The combination of the two added 2.5 to 3 mph to my top end

 

[alldodge]

Some things don't add up with the boat, well at least for me (I own one). Have a hard enough time with an Alpha Gen 2 behind a 5.7 on this boat with a 1.62 or 1.65 ratio. Most these boats (due to being heavy) all had bravo drives. Even with a Alpha it should be closer to a 2.0 and think that would be a 1.8 something

If you run the numbers using BBlades calculator then it looks much better at 9.88 at 4200 rpm
Using the same calculator for the 1.65 it shows

http://bblades.com/propeller-slip-calculator/

 

[thumpar]

Is this GPS MPH?

 

[Dcmphee]

Yes the speed is GPS calculated. Engine number is OK162850. It was a 2 barrel, and non vortec roller cam motor. I counted the teeth on the upper case, 24 teeth on both gears. It now has a 1409 carb with matching intake.

the boat runs awesome now, plugs look great and compressions is all 155 to 160 on all 8. Just wasn’t sure if I was leaving some performance on the table due to the slip numbers I was getting on the merc Calculator.

 

[alldodge]

24 teeth on both gears.

Think that comes out to a 2.0 which would be what I would expect

 

[Dcmphee]

My boat is a 97, looks like the 24-24 gear set lines up with 1.62-1.65 with my engine code no?