so this may be a dumb question but I have a 3 blade 25p prop what would I gain if I went to a 4 blade 25p prop. someone was trying to sell one for $300 on CL.

More transom lift. But more is not always better. It depends on the application. Need more info. If your boat came w a 3bl, I'd prob. stay w that. The manufacture ususlly spends lots of money on research on what works best. One of the pros on OSO will chime in w more info.

You will lose about 300-400 rpm at WOT with the same pitch. That can be fixed by getting them labbed. You will most likely have better cruise speed.....less prop slip. May loose a little at top end. I went from 4 blade to 5 blade. Had 28% slip at cruise with 4 blade. Had 13% slip at cruise with 5 blade Maxximus props. Since I spend 99% of my time cruising, I like more blades myself. Better gas milage.

what kind of boat/power do you have. i figured over 25% slip at cruise also and keep wanting to try a 5 blade but keep putting it off. did it hurt your top speed? what size 4 blade to 5 blade switch did you make?

Depends on the boat. I have found if you want speed the Mirage is the best, as long as you can get on plane. If you tube, ski and make a bunch of tight turns the Bravo 4 blade or Hydro 4 blade work well.
Where do you live in STL and were do you boat at?

It depends on what props you are talking about. There are tons of brands and types of both 3 blade and 4 blade props.

I have a 1994 Cigarette TOP GUN. It weighs 11500lbs with no fuel. Twin 600hp 502's. I originally had 4 blade 26 pitch clever style Hydromotives, which I still have and are for sale if anyone is interested. I was underpropped after new engines were built. I had at least 28% slip at cruise, maybe more. I would hit my rev limiter in seconds. I bought non-labbed 28 Pitch 5 Blade Maximus props. They feel 3 times more heavy than the Hydromotive. At 3200rpm, I had 13% slip with the Maxiumus, but my pitch was off. I went from 5500rpm to 4500rpm at WOT. I had them labbed by a local company and I am back at 5500rpm, but now have 22% slip at cruise. I still need a little more cup to drop it down. I'm not too happy about the Lab job that cost me $1000.
I wish I would have called BBlades.
I think they have a demo program or something.

I think I lost some top end, but I can't confirm.
By the way, the 5 Blade Maximus will create a lot of stern lift and the only weigh to change that is by getting them labbed, which I think creates SLIP.

Urban, you gain 1000 RPM just by labbing the props? Doesnt sound right. Usually gain 2 to 400 RPM when labbed properly. Sounds like your just slipping. I would call Brett ar BBlades......

Thanks for the info I think I am going to stay away from the 4 blade I don’t do a lot of tubing or skiing right now b/c my kids are still to young and I don’t want to lose any of my top end speed. JeffswavI live in Wentzville, I do all of my boating at the Lake of the Ozarks.

They changed the Maximus pitch from 28 to 25-26. The first time around, it slipped at 28% at cruise. They added more cup and now it is at 22% slip at cruise. I need to test my WOT to see if I need anymore cup. I sure miss my 13% slip at cruise that I had before it was labbed. My plan is to test my props at WOT this Saturday.