prop advise for baja 275
 

we have a baja 275 wwith ilmor 625 v10 bravo XR
we try to pick up some speed .
propellor bravo 1 ,25 lab finish, 5900 rpm,74 Mls
what propellor should I try to pick up a litle more speed?

Do you know your drive ratio? I know I maxed my pitch out with 2 people in our boat, but have to change props when 4 or more go out with us, when we ski/tube....a 25 seems slow at 72...a friend of ours has a 502 mpi on a 24 footer turning a 26 bravo 4 blade getting 78 gps'd. I would use a prop calculator after obtaining your drive ratio, however they are only theoretical values. When I went from a 19 to a 23 mirage.....talk about a maaaaajor change. Although we were close to the values, it totally changes bottom end and handling. I would also consider how many people you plan on entertaining as well.

i run a 26 3 blade on my 27 but only has a 454. tops out at 55, see if a friend or someone around ya had a 26 u can try for the day. thats what i would do.

prop baja275
 

drive is 1:1.5 if you put it in a calculator 16 % slip, is 16 % acceptable ?

16 is a little high, 12-14 seems to be normal, single digits would be perfect setup. Try a 26p bravo 1 4 blade

16 is a little high, 12-14 seems to be normal, single digits would be perfect setup. Try a 26p bravo 1 4 blade "

I will be sursprised if he can get a 275 hull to run fast with slip numbers in single digits as the hull is about identical to the 272 and most of the fast ones includiing mine have always ran the best numbers with slip in the range you are seeing (15-20%). Now is your boat going as fast as it can, most likely not. I do see that the hp peak is at 5800 and you are past that, does it hit 6000 instantly or does it build up to it there? In comparison my 272 runs 74-76 under PERFECT conditions turning a labbed 26 pitch around 5400-5600 when running with my blower belt off (motor made 655 gross hp at 5600 on dyno) and slows down to low 70's with full tank of gas, full load of passengers, etc, post what you end up with as this is great stuff, Smitty

If you increase your pitch you are going to decrease your rpms...if you do this, will you be able to decrease slip to increase speed? Else, you are going to decrease top end...

[QUOTE=jctexas07;3887259]If you increase your pitch you are going to decrease your rpms...if you do this, will you be able to decrease slip to increase speed? Else, you are going to decrease top end...[/QUOTE
Increasing pitch alone isn't necessarily going to lower "slip" its only going to lower rpm and once you get motor away from the power band boat will most likely go SLOWER. Going to a prop with more surface area/blades or effiecient design will lower slip but again as slip lowers you will get away from the power band peak and again may slow boat down. It may be possible to lower slip with a ideal prop and then have to go down in pitch to keep motor near its power band. Lets say your boat "peaks" at 600hp at 6000 rpm's, lets say it takes 600 hp to move your hull thru the water at 75 mph, your current prop turns 6200 and boat is running 72, you go up slightly in pitch and at same time a prop expert does some work to your prop to make it more effiecient, now boat goes 75 mph at 6000 rpm's and your pretty happy.
Scenario 2 (which is more real world)same everything except instead of having a custom tuned prop built you go up from lets say a 24 to a 26 , if your boat could turn it at the same slip you would now go 78 mph, problem is the extra 100 hp you needed to go 78 isn't there so instead boat just lugs at same speed and goes 5700 rpm's or maybe goes a mph or 2 faster and is below hp peak.
The boat would also then be a pig accelerating because it would be working harder to get to its sweet spot. Propping boats can be alot of trial and error and certain hulls have a "normal" amount of slip that just goes with the hull.
My own boat, I chased after lower slip numbers before convinced that there was some speed I was leaving on the table somehow, tried a 5 blade , boat cruised at a incedible slipe rate under 10%, it also torque rolled and went SLOWER at wot, then it sheared off a prop shaft. There is gains to be had, they are just smaller than what most would think they are unless you have the totally wrong prop on your boat to start with, Smitty

baja275
 

thanks for replay, that i was afraid of, that the hull is not faster.i would love to see 80's
and a shorty will this help?

What is your prop centerline now? This is measurement of distance your propshaft centerline is below your hull. I gained 3 mph or so with a -2 shorty bringing me from 8" up to 6" below pad. I had some ride quality issues with the shorty but hopefully my new prop fixed it. Smitty played around with a ton of setups with drive height in the past so I would keep to what he recommends and dont go off results with other hulls alone. For what its worth anyway....once the go fast bug bites it seems the search never ends :lolhit:

A shorty may or may not help, there have been alot of claims of great increases, none of which I ever saw on my boat. My prop c/l is 7.5" BUT my boat runs near the 100 mph mark and when it runs into the 90's it "climbs" up out of the water and I believe it acts like it has a higher prop center line at those speeds and thats my theory of why both a Imco shorty and exstension box both killed handling and top speed in my boat. Yours may be different however as you are running much slower. I bought a labbed 4 blade 28 pitch from Greg Hittner at cutting edge props to run with 1.36 gears in my boat, before I could get any real world results I totally destroyed everything in the lower including the case BUT a good friend of mine tried it on his Checkmate that runs in low 70s and his boat saw solid gains over other 26/28 labbed props that I had done by someone else so small incremental gains can still be had , you definately need to try a 26 labbed since you are over-revving slightly, maybe have yours tweaked slightly as you are close to the right rpm.
Does your boat crawl to 5900 or get there real easy, where is your rev limiter set? Have you verified the tach calibration (compare it to a digital timing light), you have to just keep trying and you will find a little speed here and there, Smitty

Am I missing something? It looks like jeromeke has a slip % of over 20%.
Shortys on these hulls are most often a mistake unless the boat is close to or can do triple digits. Or, if speed is all you care about and carrying loads isn't a often occurance.
Remember, every identical boat is different. The correct recipe 26 Bravo 1 should get you the best all around performance. We have been using them in various configurations for almost 20 years on these hulls. There are starting points that must be followed by subtle modifications.

I'm still concerned about your slip percentage. It is true that in certain instances, true V bottom boats can obtain their best top speed numbers with slip numbers in the upper teens. However, this can compromise planing and fuel ecomomy where you operate the boat most often. Determining your ultimate goals is also a big part of the equation.

Good luck and above all have fun.

Brett

thanks for the info,we wil try a 26

I have a 27 pitch spinnille that would work great on your boat , lots of bow lift big round ears , there iis 28 pitch labbed for sale on the oso. The fasted i have every runs was with a 30 labbed bravo 1 83 mph at 5100 rprm i have some left in the power range put some new eddie marine thinders on it that may give mine aa little more rpm . I have have 4 blades know can send you pics of mine , buy mine i will buy the 28 . If it dosnt work well send the 27 back and i will send the 28 . just like to play with props did some bottom work also . I think i am going to put that spinnille on my rev limiter ' IM me we can talk...i really like the spinnille but i also have a 30 like it
your boat loves bow lift to make it go
scott

I see you're from the Netherlands. Is your "74 mls" you posted in US miles per hour or Nautical Miles per hour???
That could make a huge difference and is it taken from a GPS speed??

I wasnt saying if you do this it WILL decrease slip. It was a question posed to would it if you did?

[QUOTE=articfriends;3887330]

prop advise
 

We run a normal b1 26
74 mls
5600 rpm lots of shine walk

we tryed a mirage plus 25 75 mls but a smooter ride a am thinking abouthe a mirage plus 27 labbed, anyone a prop for sale?