Hello,
1st let me say love the site and have learned a lot.this is my first post so any help is appreciated.
myboat-24' Lavey craft w/502/500 xr drive. had a 26 pitch 4 blade running 5100-5200rpm. I just got a new prop 28 pitch and had it labbed.boat is faster out of the hole and seems about 6-7 mph faster top end.havent had a chance to gps it yet.max rpm 4750-4800

my question is should i get it tweated some more to get rpm's back up to 5 or higher? My prop guy says it might only gain 1-2 mph and my friend/mech says powerband drops after 4800 so not really worth doing. To me 2-3 hundred rpm seems like a lot to gain more speed but am i just trading rpm for speed..kinda lost at this point

First, welcome to the board.
Second, if the 26 Bravo 1 was a stock propeller, the Lab Finishing you had done did nothing to gain rpm with the 28 like it should. When we Lab Finish a propeller we see 150-400 rpm gain depending on the recipe. It can be designed to be less for special circumstances.

Something else doesn't add up. If we use a hypothetical speed at 5200 with the 26P propeller at 11% slip, then go to the 28P at 6mph faster, your slip% drops to under 4% and that is impossible with your hull.

We need accurate speed numbers to give any better advice. Accurate speed numbers with both propellers. My guess is both WOT speeds are going to be much closer than 6-7 mph.
Also, there may most definitely be room for a speed improvement due to a rpm gain with the 28.
Calling us may be a better way for me to explain my thoughts to you.

Brett

Brett,
thanks for the info..honestly i dont wanna waste ur time on the phone since i already did business with this shop and they are willing to tweek it for me free. but i will def use you guys next time.
i did not have a gps and i was just using my speedo in boat but last year wot on the 26 was 72-74.the new 28 labbed prop was 78-80.speedo tops out at 80 so dont know how accurate it is but i do know at 72 it was accurate. i assumed the labbing was done lightly as to not over do it and assumed if it was a stock 28 my rpm's would have been lower.when i talked to a couple people they said yes i can have it labbed more to get back upto 5100 but im trading off speed to gain rpm.in my mind im losing some of the pitch to gain rpm's so not much to gain above 4800 and its kinda safer to stay at 4800.i do see how maybe more labbing could be better but if only to gain 1mph i'd rather stay safe at 4800 if that makes sense.now if we r talking about gaining 3-5 mph than i'd do it

My point is........

Your rpm level is just where it should be going from stock 26 to stock 28 suggesting the 28 hasn't really had anything done to it. Just the pitch change should be a 400 rpm drop. If there is truly more HP at 4800 than 5200, the stock 28 could create more speed just by running at 4800. Highly unusual to gain 6-7 though.
Also, the speed with the 28 isn't 79ish because I doubt your only running 4% slip.
You mentioned 502/500. Is this a blue motor or a 502 built to push 500HP?
I don't mind answering questions for you. That's what we are here for. Hopefully I can clear some things up for you.

Brett

If its a Merc 500HP or EFI, they make more HP at 5200rpms than at 4800rpms for sure.

Its a blue motor/500 hp. I was told it would have dropped more with a stock 28.so i guess i need to go get it labbed more.

Sounds like you need to get it Labbed to begin with. 1 inch of pitch is approximately a 200 rpm loss. So, your 28 is still a standard 28. Sorry to be harsh but that's what it looks like.

If it is a blue motor I would go ahead and prop it above 5000. If it was mine I would prop it at 5300 because they still make HP there and I would like the throttle response.

I know you spent money elsewhere. Sorry you may have not gotten what you paid for. I see this all the time. These days "everybody" can Lab Finish propellers...............What questions do these shops ask prior the work and do you actually see results? Get baseline numbers before you have work done.

Brett

they did ask all my previous numbers. i talked to lavey to see if i could run a 28 and they said yes if its labbed so this shop said they would lightly lab it and will rework it from there as needed..i do believe they know what they r doing,i just didnt go back because a mech/friend said i wont gain much..guess i shouldnt listen to him..i'll keep u guys posted and bblades thank you for the info

Best of luck to you. Again, I don't mean to condemn the work you had done. You just don't have a rpm gain like you normally would and In fact you have no rpm gain that I can see. I'm sure the folks you worked with will explain their process to you.

By the way, did you run the prop before the Lab work? If not, this is a prime example why we like people to do that.

Brett

brett, no speak your mind..lol..im sure there r a ton of people that screw it up but i gotta give these guys the benefit of the doubt as they said they would work it for free to where i need it..no i did not run it first because the guy from lavey said it would have to be labbed to run it which again is why the guys at the prop shop did a light lab.if they cant get it right i know where i'll send my business