Vinny P

As some of you may have seen from my previous threads, I am building a 540. It should come in at about 675 hp @ 5500 rpm and 680 torque @ 4500 rpm. I will have this motor in a 259 Convincor, weighs in at about 4500#. I already have full dual ram hydraulic steering, Dana Marine HP 1000 tabs. So the back of the boat is set-up to handle the power. Now all I need is a better drive.
I have a possible deal going for a Barvo 1 "XR" with a Sportmaster lower. Standard length, but with 1.36 gears. I have called 2 drive shops, they told me that I would be better off with the 1.50 ratio.
What are the goods and bads about running a 1.36 with a smaller pitch prop vs. a 1.50 with a bigger pitch prop?
Also, how involved and how much would it cost to have the gears changed to 1.50 if it needed to be changed?

Thanks guys..

Havasu Cig

I had a 26' cat with a blown 800 and XR with 1.50's. Running a 32" 4 blade prop the boat was almost imposible to get on plane because of prop blowout due to a high X dimension.

I dropped down to a 30" prop and 1.36's and it solved the problem of getting out of the hole. The downside was a loss in midrange acceleration. Cost to change the gears through Teague was about $1500.

I would think you X dimension would be more conservative with the hull you have, and your hp is not to high so the 1.50's should work for you.

krypto 1 in CT

most prop and outdrive shops that i talked to said dont drop down to a 1.36 until you run out of prop pitch which means around a 34 (not sure how good a 36 is).most of the time the boat will be a couple mph faster with a 1.50 and the taller prop.i think there is less of a chance of breaking the prop shaft with a 1.36 and smaller prop though.

MESABALANCING

CHECKMATE
LET ME TELL YOU THAT WITH THE TESTING WE HAVE DONE ANYTHING THAT DOES NOT HAVE A BLOWER AND MAKE 800FT LBS OF TORQUE OR MORE YOU WILL NOT BENEFIT FROM THE 1.36 AT THE BEGINING OF THE SEASON WE TOOK MYPANTERA28 ALBERTS BOAT THAT WE RACE HERE AT THE SHOP T O TEST PROPS AND WE HAD THAT RATIO WE FOUND NO ADVANTAGE ONLY DISADVANTAGE WE CAME BACK TO MIAMI AND REGEARED THE DRIVE AND FOUND ALL THE SPEED WE NOW HAVE WITH STD PROP DIAMETERS AND PITCH WHICH MAT AT THROTTLE UP HAS FINISHED DONT MAKE OUR MISTAKE IF THE PRICE IS GOOD BUY IT BUT RE GEAR IT.HOPE THAT OUR INFO HELPS YOU LAZ MESA WWW.MESABALANCING.COM

Vinny P

Thanks for all the help.

dlbCheckmate

Checkmate454mag, I have a 251 convinsor running a 1.5 bravo. Like you I had the chance to buy a couple of spare drives and lowers at a good price but they are 1.36 gears. I have a 572 BBC motor that I wanted to try the different ratio's on. But the motor did not cooperate and overheated a rod bearing and wiped out the motor. I will still try my experiments, Imco shorty, Extension box and 1.36 ratio's , just not quite as soon as I hoped. I freshened my old motor ( thanks to Jim V for his quick turnaround ) so I can at least boat some this year. PM me and we can talk about the hull and power. Dave B