2 Trick Rick

Thanks, Do you live near Baja MX?

articfriends

iTrader: (1)

There is baja acres track just a few miles down the road from my house if thats what your talking about,Smitty

2 Trick Rick

Yep, I have been going to that place since 1986.

Strip Poker 388

iTrader: (6)

Smitty thats the first pick I ve seen of the twisted shaft whos was it?

rob

articfriends

iTrader: (1)

That was a max worx shaft after 10 or so wide open passes with a 5 blade 28 maximus I tried on my boat.The shaft was 5 seasons old and never had the slightest indication of damage even with the 32 pitch 4 blade,the 5 blade was just too much and was torque loading the boat. It was a std dia billet shaft they were making before the xr stuff even came out,you would thiink it would have broken were it is smaller but it didn't,the xr style billet max worx shaft I replaced it with is no bigger in the spot were it broke so I am staying away from 5 blade props.The lower gears however still looked like brand new from the cryo/polish treatment which is a good sign that it is going to help greatly extend the gear life,Smitty

KAAMA

iTrader: (1)

Smitty,....So then, cryo treating the splines on the shaft won't help strengthen or save the shaft???---just the gears only?

articfriends

iTrader: (1)

Kaama,the max worx shafts are made out of a exotic alloy that can twist somewhat and return to its original state without breaking,it goes thru a exstensive treatment and is sold to them by the inch,I feel the torque my motor makes vs the dia/strength of the shaft compounded by the overall gear ratio (around 1500 ft lbs) exceeded the shear point of the shaft when I added a huge prop with virtually no slip. The cryo treatment process stabilizes the grain structure in a common metal like 8620 steel (it is soft with a hard surface like a egg shell),the polishing and treatment process makes the surface where the oil film/contact (or pinch point) comes together less likely to gall so its not whats needed to make a shaft under a severe torsional load stronger. My 960 ftlb tq motor puts the same amount of stress on the prop shaft when using 1.50 gears that a motor making 1100-1150 ftlbs would with 1.35 or 1250 ft lbs with 1.26 gears would to keep things in perspective,large 5 blade props are the quickest way to guarentee failure on a bravo drive,Smitty

zt260

Smitty,

I know you had troubles with the 5 blade, and I understand your point. I just think there’s more to 5 blade bravo failures than that. From my experience the trick is to maintain some slip. If your hull runs great with a 4 blade at say 12% slip I would not recommend a 5 blade unless you plan to raise your propshaft an inch or two. But if you’re at 20% slip, and can barely get on plan with a 4 blade than a 5 blade could work out great. I added a 5 blade Maximus and a 2 " shorty and picked up about 7mph. Granted its a Bmax, but I have broke propshafts with 4 blades, and since the switch I have not broke another. Now I know I just screwed myself.

Dave

Vinny P

I broke an Imco SC lower shaft last year with 680 hp, 660 torque on a 25' Convincor, spinning a 25" Hydromotive P5-X.

articfriends

iTrader: (1)

Dave,you brought up a good point because I really generalized when I made that statement. On my particular application at the time I had raised the prop with a stellings box plus 1" and had developed terrible blowout & porposing problems with my 4 blade 30 and 32 labbed props. They normally slip between 18-28% on my boat depending on speed. The boat had lost a solid 3 mph from the stellings box in the plus 1" position along with the nasty drivability issuses. I added a 1" spacer and got rid of 80% of the drivability issues but lost another 3 mph on top of the 1st 3mph I had already lost. I borrowed a virtually untouched 28 maximus which slipped around 8-10% on my boat which made it torque lug terribly. After a few passes I put it on the trailer because boat was so unsafe,it would hook and turn to left hard when backing out of the gas plus was tq steering awful and transom lifting plus running even slower yet than any of the previous set-ups. I came back out the next day with the 1" spacer removed,the slip was still around 10% and boat still felt like it was lugging and going to break something. Around my tq peak (4700-4800) the boat normally goes insane and feels like you hit a 500 hp nitrous when you pin the throttle,sprinting to 5600 in seconds,building to 5800-6000. With the 5 blade it would sorta lug like it was going to blow the drive apart and would take 20-30 seconds to pull to 5600,after 1/2 dozen passes or so it sheared off the prop shaft. It had still came no where near its best top end,was about 8 mph short. I talked to julie at throttle up as I was considering going shorter yet on the drive and experimenting with maybe a cutdown 5 blade maximus or p5x but she was very doubtful I'd get my 8 mph back plus a measurable gain and I didn't want to spend another 5 grand on a shorty and numerous 5 blades just to destroy more drive parts and fight to get back to my old speeds without a further gain. I pullled the box of instead and am going back to my original set-up. My boat has always flatout ran the very best with its prop slip in the 20 plus % range,when I have tried props that lowered it,it only ran slower and took considerably longer to accelerate.
So I will restate what I said-if a boats given set-up runs a 4 blade prop with a high slip number and likes it and your drive is staying together with serious power,its going to come apart if you drop the slip considerably with a 5 blade if your already right on the edge. Everytime I see someone selling a pair of max worx drives and they are bitczhing they only held up 10 or 20 hours,they usually have a picture of them on their boat with 5 blade props. To run something like a maximus it definately needs to be cut down or real high so it has some slip,Smitty