If you had 2 props the same pitch one was 1/2" less in diameter. What would the performance results be ? Would the smaller diameter prop have simular or higher top end(assuming you'd be able to turn more rpms because of the smaller diameter) ? I'm guessing the larger diameter prop would have better bite/holeshot ?!

Is there any method to this madness ?! Any one with real life experience in this ?

Thanks

There is an exception to every rule, however. larger diameter increases stern lift, smaller decreases (the bow will lift). More blades also increases stern lift. Use the diameter and rotation (out lifts the stern) to adjust boat attitude. You will probibly see differences in slip. Figure it out mathmaticly after you test run each setup. Prop pitch should stay consistant no mater the diameter. The slip may change with diameter changes, this may effect your speed. There is no substitute for testing, just make sure your test are in the exact same conditions and fuel loads.

You see...sometimes, amidst all the chatter, some real great information comes along! Thanks TNT, I had this same question this past weekend when deciding which props to put on my boat.

I had two sets of 3 blade cleavers(over hub) a 16X22 and a 15X24(which were a little nicked up) and was wondering what the net effect of the larger diameter/lower pitch prop would be...

TNT, in your professional opinion, what would be the best prop selection for a 35 Cafe Racer with 540s(roughly 600hp) and TRS drives be? The 16X22s ran 5100 with the old 420s this past weekend.

Thanks!

Sean,
The best set up in my opinion would be the Merc 4-blade Bravo one props. You'll see a remarkable differance over the old over the hub 3-blade cleavers. I had a new Top Gun in 1987 with those props and they were the hot set up at the time. The Bravo ones will make you think you bought a new boat. I've seen the best results turning them in, however the maneuverability at the dock may suffer. In the TRS years there were some Cafe' Racer's with a notch transom. if yours has one you'll have to try both rotations to see what works best for you. As for pitch, depends on the max RPM you want to spin your motors. You'll have to start some where so I'd try 26 or 28 pitch with 600HP. Get your base line then go up or down in pitch as needed. GOOD LUCK!

P.S. I have a set of used 22 pitch Bravo One props for sale, if you keep the 420's in the boat

Thanks TNT...that's pretty much what I thought as far as pitch on those Bravo I propellers...dunno why, but I was thinking of staying with the cleavers, but on your suggestion and that of a couple of others, I'll be looking at the Bravo I props...

The 420s are already out and on the floor...changing the accessories over to the 540s this weekend and hopefully we'll be on the water next weekend.

I spun the 24" Bravo I props in on my 28 Cigarette and hated the way it docked...just didn't respond the way I wanted it to. Spinning in will increase transom lift right? The Cafe has no notch and we had to trim it to about 5 on the Bluewater indicators before it would loosen up(with the 420s, 16X22 cleavers, spinning out)...

I'm inclined to spin the Bravos out, and I think I know the answer, but what will spinning them in do? My guess is more transom lift and high top end...thoughts?

thanks again

Turning the props in decreases stern lift. You'll have to try both combonations to see what works best for you. In my experience the cleaver props would be the least desirable props to use. If you want to try anything else besides the 4- blade Bravo One, you could try the 3-Blade Bravo prop. It would be my second choice and are more readily available on the used market. To anwser your question, turning in usually reduces the slip factor and gives the boat a better attitude. This is very noticable on a non stepped Cigarette with bravo drives, usind 4-blade Bravo Ones. Boats with a transmission, like yours, (center of gravity is further forward) can work either way depending on boat speed. There is a sweet spot for the angle of attack. You just have to test different combonations to get the optimum performance. This last bit of testing takes a lot of time, if you have it you'll get the last mile an hour out of the boat. The original combination with the 4- blade bravo Ones (in the correct pitch) turning in will probibly be your end result, in my experience.

The answer is another question: "How much blade area is needed to absorb all your horsepower, but not too much blade area because then it's a waste of power turning it through the water." For most of us changing blade area is done by changing between three and four blade props, or changing drive height, which has the effect of changing the effective blade area. TNT is right, testing is the only way to find out.

Cutting down diameter is fine tuning for sure. For example, my boat is faster with three blades, but they blow out too much. Four blades stopped the blowout, but I lost a little speed. Somewhere in between a larger diameter three blade or a smaller diameter four blade would maybe give the best of both.

Oh no, another prop variable- "diameter". So test and get the best stock prop, then have it labbed, test, then cut it down 1/4" and try again, then another 1/4" until you go slower. Now you've ruined the prop but you can have your 'best' result prop duplicated. I'm glad I have a single screw.

Thanks again for the info

Hey T-N-T you are a wealyh of Info!!! One question....I heard that 4 blades are tougher on Bravos than 3 blades. They hook up faster or something. any truth ??