prop pitch

03-13-2003, 03:16 PM

I run Mirage 23's and get 64 mph at 4600 rpm. twin 7.4 mpi Merc I/O's Also lab finished Bravo 1 4 blades, 62 mph at 4600 rpm.
QUESTION: If I were to have the 4 blade pitch changed to 25 would I pick any speed or just have an rpm decrease?
Any feedback is welcome, Thank You.

throttleup · 03-13-2003, 03:45 PM

bvs629,

Your recommended WOT range is 4200-4600. You are running on the top of that range and it is hard to say if you have a "Sweet spot" in there and where it is. I would look at your current props and try to determine if there is any adjustments that can be performed to possibly increase your speed. Re-Pitching to a 25 will decrease your RPM. Feel free to call me if I can be of assistance.

Thank you,
Julie

HOUSTONPROP · 03-13-2003, 03:56 PM

Quote:

Originally posted by bvs629
I run Mirage 23's and get 64 mph at 4600 rpm. twin 7.4 mpi Merc I/O's Also lab finished Bravo 1 4 blades, 62 mph at 4600 rpm.
QUESTION: If I were to have the 4 blade pitch changed to 25 would I pick any speed or just have an rpm decrease?
Any feedback is welcome, Thank You.

pitch the 23 up to a 24 pitch add cupping and lab the prop this will run the fastest/also the labbed 4 bld possibly can be thinned out more and add 1" of pitch to achieve a tad more speed but always the mirage will be the fastest as you know/Darin/Houston Propeller SERVICE

03-13-2003, 07:43 PM

Thanks for the information. I think I will try to pitch the 4's to 25.
There is a service here local that can do it for a good price.
Pitching the Mirage's up to 24 an labbing them is a little more expensive but a good option, besides they have the Baja logo on them when I bought the boat.
Thanks again!!

blue thunder · 03-13-2003, 08:33 PM

As long as the rev limiter does not become an issue, I would repitch the 23 mirages to a 22 pitch taking the rpm to 4800. In my opinion, 4800 is a good max wot rpm for your engines. Let'em sing

Good luck,

BT

HOUSTONPROP · 03-13-2003, 11:25 PM

BVS629 Glad to be able to give my 2 cents /will be glad to work with you if needed/Darin

03-14-2003, 06:51 PM

Thanks to all My rev limiters are are 4700. Thanks again.
Darin If I do anything I'll let you know how it turns out
BVS

blue thunder · 03-14-2003, 08:15 PM

Then I would change my ignition to one with a 5050rpm rev limiter and still repitch to 22.

BT

03-15-2003, 04:35 PM

Quote:

Originally posted by blue thunder
Then I would change my ignition to one with a 5050rpm rev limiter and still repitch to 22.

BT

What would be the effect if I were to d this and run my present
labbed 4 blades, 24' pitch.
I know pitching to 22 would let my rpms come up. but how would that increase the speed with less pitch. Curious reverse logic.

Thanks awaiting your reponse,

BVS

uppy:

blue thunder · 03-15-2003, 09:35 PM

Changing the ignition to one with a higher rev limiter will not affect your achievable rpm. Changing the ignition and keeping the same prop won't change anything. You need to repitch the mirage. Mirages seem to give the best top end (depending on boat) . Bravo1s give the best cruising range, but generally you will loose a little on the top. Your engine should like 4800 as well.

Just my opinion... I am sure the businesses that posted before me could give you better advise

Good luck,

BT