Its Chine Walk
 

Would like some advise I converted from Alpha to Bravo ITS started with a 15 inch 26 pitch bravo one 4 blade 620 hp 24ft baja,could only get 5000 rpm 60 mph motor is limited 6000, lots of chine action. droped prop to 14 1/2 thinking I would pick up 4-500 rpm but didn't lost 10mph and lost 200rpm. I also put Edie tabs very touchie.

Richard Cuny

Your slip is WAY high. With proper slip you should be at low to mid 70s with a 26' prop@ 5000rpm. How deep is your prop compare to before, with the Alpha?

PAYTON
thanks for your reply i measured the two drives the shaft is about 3/8 lower but the ITS is 7 inches back from the transom witch equates to being lower.going to try two different props tonight loaned to me. My intention is to put a shortie on but was going to wait till next season just spent a lot this season with engine,ITS new dash ,gauges,throtel ,tabs and indicators.
Payton dosen't slip increase RPM my engine should run 58-6000 not 5000
Richard

Your slip is very high at 24%. It does seem strange that the motor only pulls 5000. If the slip was hanessed to 12%, you would fall to 4200 pm. 620 hp on a 24 Baja should pull harder than that. I wonder if something else is happening with the engine besides the unusually high slip numbers?

Thanks For Your Reply
I Have Tried 5 Props I Have Today Used A 22pitch Bravo One It Ran 5600 Rpm 60 Mph On Gps Seems Any Prop From 23 ,22,26 All Run Around 60, Rpm Varies Seems My Its Has Lowered My Drive So Much And My 620 Hp Lifts The Boat So High It Gets Very Hairy At 60 When I Look At How Much Boat Is In The Water At 60 Seems It Is Riding On The Tabs Not Two Or Three Feet Up Fron The Transom. Excuse The Caps.

Richard,
I just swaped out a bravo 1 for a complete ITS assembly and have very good results. I needed full hydraulic and did it mostly for that reason. Handling has improved, I picked up a few MPH and a few hundred rpms. Most of this probably is due to new CMI exhaust and having injectors cleaned and flow tested. Oh, 24 Pantera no shorty, standard ITS. I also figure it dropped my depth an inch or so so my propshaft depth below the hull from 3.5 to about 4.5 inches. Hope this helps. Good luck.
Greg

GREG
Thanks I will measure my prop shaft. Friday was my first poker run to Atlantic City very exciting my friend and I with extra tools both over night clothing and a large ice chest, 100 gallons fuel the boat ran 65 very littel chine walk .
Richard

Its Xr Bravo One 620 Hp 24 1987 Baja
 

I have had some input on this application my prop shaft is 7 3/4 inches below the bottom plain of the hull boat rides very high chine walks and with a 23-24-26 pitch only runs 60. Howevewr this weekends poker run with an extra person and two overnight bags,ice chest full,full fuel tank, extra tools and extra props it ran a honest 65 with minimum chine walk,ran 5600 rpm best ever with a 23pitch 4 blade quicksilver off shore prop. Any help would be appreciated.
Richard Cuny

Richard, I would ask other Baja owners on another thread exactly their propshaft heights/depths are and if any run extension boxes to give you an idea of where you stand and if you should be going higher or lower. I would be guessing on your hull. If you have not searched it, you may also find some info that way. Good luck.
Greg

Richard, even 65mph is way below what your rig sh)ould run with over 600 hp. The high slip number does not stack up with your low mounted propshaft...unless you are trimming way too high/out to find some speed. This would also explain the chine walking (particularly in smooth conditions). The increased speed and less chine was probably due choppy poker run conditions (which our non-stepped Outlaw hull like).

Get that propshaft to hull dimension up to around 4-5" and you will need less trim angle to get your speed, and you will be a whole lot faster. Remember that a 7" setback is pushing the drive into even deeper water, and that is all just drag. Trimming the drive out to lifts some of the metal out of the water, but then you start to lose the forward thrust. The amount of trim you need to lift the bow should only be about 4 - 6 deg over parallel to hull.

I would recommend a 2" shorty.