I am running a 1992 Liberator 221 with a 502. Here are the numbers.

Stock:
5200 rpm with a 14.5x20 Raker prop would see about 62mph giving me about 11% slip. (Engine RPM as measured with Snap on Tool on #1 wire, GPS speed)

Post Engine Build:

5050 RPM (engine built to 5500rpm max) 14 3/8x21 Ballistic 68.5mph (in the conditions/load that day) which give me about 3% slip and I know that is not reasonable.

The prop is acting more like a 22.5" prop. It's an OMC drive so I don't have a ton of options to try.

Ideas? Thoughts? I'd like to bring up the max operating RPM's a bit as the engine made peak power about 5150. Will labbing help a ballistic prop? They are already fairly thin.

Actually you have many options, you can run any Merc prop with the proper hub kit. I am running the same hull with the stock 502 and a raker, I want to try a Tempest and an Enertia on mine this summer.

How heavy were you running that day? Did you buy the prop new or could it have had previous work?

Yeah I know I can go the merc route if needed. The prop was used, but it was a demo prop, it looked perfect. If they told me it was new I would have believed them. I was running full fuel with 3 adults and the normal gear. The more I read about it, it looks like Ballistic props are kind all over the map for pitch.

I've seen a best of 71.5 gps. It likes a good chop on the water to get the last couple out of it, and that was with a quarter tank and just me and the wife. I just wonder if it is worth going any further with this prop, or try something else.

Curious, what do you see stock?

Here is what it looks like now.
https://www.dropbox.com/s/q2fub78lkhblq83/502.jpg?dl=0

https://www.dropbox.com/s/bn55uy5hp7...%20pm.png?dl=0

Did you run it with the prop you had with your stock setup? If so, what were you seeing? How much increase in horsepower post build? I'd PM Brett at BBlades for his thoughts.

I've seen a best of just over 65 with just me and under a 1/2 tank of fuel, I am def getting the most out of it, I also have heard mixed things about the Ballistics, I ran one on my first Libby a long time ago and loved it but it was also one of the "Atwood" Ballistics which had far better consistency

If I keep it I will be doing a cam and exhaust at some point in the future...

Did you try a 22 or a 24 Raker on it?

5050 is fine if peak power was 5150.

I've tuned several boat where best mph was actually a few hundred rpm under the max rpm on dyno.

I guess this can be the difference between WOT under real conditions vs a dyno sweep test.

I did, I could easily blow past 5500, since that was the case I bumped the pitch right away. Dynoed 539 through wet manifolds.

Gen V converted to full roller with Bob's help.
Port Matched (not full porting) on stock Heads
Minor Valve work
SM Manifolds
Marine Kinetics Cam with all of the roller pieces Bob recommended
DUI ignition ilo the stupid OMC spitfire system
Scorpion Rockers
Bump in compression
EB High Rise Intake
850 Holley Mechanical

Some other little thing Bob Suggested.

Maybe if nothing else I could have BBlades check the prop, or recommend something.

I would love to try a Raker 22", if I had one available. I actually had one previously and sold it before...

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