29' Cat-V8 Power..Need Prop Help!

[crazyeights]

Hello. I have a 29' cobra cat with twin big bore V8 outboards (350hp) each. The boat is currently set up with 6 inch set backs in combination with power jackplates to adjust motor height. Gear ratio is 1.76..Low water pick ups..Trying to establish prop set up for max performance. Boat came with 28p Spinelli 3 blade cleavers that turn 6100 rpm an runs 82-83 mph. Considering 4 blade cleavers or higher pitch 3 blade cleavers. Not sure which direction to try? Slip factor currently 10% with current props...Go higher in pitch with 3 blades? Try 4 blade cleavers? Any input on prop selection?

[joneill]

i like this boat, havent seen it in a while, any pics? thanks

[crazyeights]

Only pic I have on me..This is an older pic prior to me changing out the motors with the V8s..See you on the bay.

[STV_Keith]

I'd say try some 28 Bravo 1's. Some more stern lift, and probably less slip in the midrange, plus more diameter (15-1/4) so you might be able to run the gearcases a little higher on the plates.

BTW, love your screen name...

http://www.speedcraving.com/scarab/licenseplate.jpg

[crazyeights]

Wow!!! Nice lic plate. Sure would look good on my vehicle. What do you think about 15x30 cleavers? Never considered bravos

[STV_Keith]

Not sure about the cleavers. I know a lot of the big cat guys run them, but the Bravos work real well too...especially with the larger diameter and blade area being a 4-blade.

[olmo40]

I run a 30 Skater , depending on conditions my 3 and 4 blade cleavers are fastest ,However for everyday boating i run B1 s they are my favourite.Im in agreement with Keith

[crazyeights]

Thanks for the input..In agreement on pitch (b1-28P)..In regards to cleavers do you prefer 3 or 4 blade?

[olmo40]

I prefer the 4s on my boat ,The 3s are fine on the smaller cats .JMO

[JrCRXHF]

Not on a cat but my V8 likes a trophy plus 4 blade.

http://photos-g.ak.fbcdn.net/hphotos-ak-snc3/hs049.snc3/13634_175326511921_505411921_3475881_2722666_n.jpg

http://photos-a.ak.fbcdn.net/hphotos-ak-snc3/hs049.snc3/13634_175326261921_505411921_3475880_6585392_n.jpg

[crazyeights]

Just bought a pair or 30p 3 blade cleavers and a pair of 30p 4 blade cleavers..Guess I have to spend the money to know..Expensive proposition...Got to love boating to endure these expenses.

[wideglide55]

If it will only pull 6100rpm with 28s you may find 30s drop you down 400-600 rpm,especially the 4-blades.May not be able to pull that much pitch.I'm interested to know my guess is it will be slower.

[crazyeights]

You may be right..Avg is approx 400 rpm going with the 30P 3 blades. Approx 500 with the 4 blades.But know won't know till next spring..Put the boat to bed for this season.Funny thing is I ran 26p then 28p and rpm was the same but picked up 8 mph. Will see...

[wideglide55]

stock limiters are 6700,I had a 4.o Johnson on my Eliminator and it would only turn 6200 didn't matter what prop.Some of the later v-8 were detuned to keep them from grenading.If she will pull em you can go faster.Is your hull true tunnel or pod tunnel?I've seen heavier style tunnel boats that will only run with choppers if they need more bow lift.Also v-8s seem to need to be a little deeper in the water than a merc due to the weight.I honestly don't know how you keep a gearcase in one piece either,if you need parts for yours HOMEBOY on here is a friend of mine and has half a building full of fun stuff if you run OMC Wayne Taylor blocks and such.When I get enough cash a MadEfi V-8 with a 15in.mid and 3.0Sportmaster l/u will make some fun on the water.

[crazyeights]

Thanks for the input..Never considered choppers.Always thought cleavers were the right prop on a cat but your right if bow lift was needed a chopper would be the way to go..Never took out a gear case though snapped a prop shaft. These v8s have high output stators,275 heads for higher compression,relieved exhausts,velocity stacks,b reeds.and slight exhaust porting on the block.This boat should really run better than 80's which is why I'm finally putting the time into proping it correctly.Thanks for the info on parts etc..Regards!