What pitch????
 

Okay so far all my questions on my new to me boat have been answered on this forum but now I have a prop question.
Boat is a 87 formula f23sr and it has a 454 with alpha drive, its sporting an aluminum 19 pitch and I'd like to go stainless. The boat will be used for some cruising and a litle play, but also for towing my daughter and maybe another person in tubes. What pitch can anyone recomend for overall performance. I dont want to over pitch. Thanks guys, I will say this site is incredble, glad I found it.

what RPM are you turning now ?

I dont know yet, I'm taking the boat out Monday for the first time since purchase. I'm sorry I sound so stupid about this stuff but I've been away from it for ten years and I'm just figuring things out again but I love gaining knowledge. Now for the stupid question-what RPM is the max you would push a 454? I dont need to launch an engine being uneducated about this. The boat has GPS so I'll get a fairly true speed and I'll make notes of speed vs RPMs and report back on here. Thanks again.

If it is the 454 Mag you need to run from 4600-5000 RPM.
If it si the 454 non-mag then 4200-4600 RPM.

Safe Testing!

Julie

Okay guys I ran her today and heres the deal boat is 23 ft formula LS with a alpha and 454 mag. Prop is an aluminum 19 pitch. Boat ran 40 mph @ 4,600 RPMs speed was checked on my gps. Any recomendations on what pitch to go to? I dont want to overpitch or under pitch.
I will say I havent had a boat in 11 years and being widowed with a 9 yr old daughter this was the best thing I ever did and the fever is back !!! This boat is great and I feel I got got some life back. Thanks guys for any pitch advice.

Prosno, i had the same combo on a Pachanga many years ago. The layman's place to start is a stainless of the same pitch... you won't get the prop flexing under power that occurs with aluminum. You also have a 3blade prop, not 4, consider something like a Mercury Mirage... again, this is the laymans starting point.
...consider any recomendations from Julie at Throttles Up to be gospel.

I believe that you should start with a 17P Mirage Plus or possibly a 17P Vengence for starters. Both of these props will get your RPM up and speeds may come with it.

Julie

Julie my thought was this, I can get more RPMs no problem but I dont feel comfortable pushing a big block too high on the rpm scale. I was thinking and again I'm new to this. a 21 pitch so I could get more top end and better fuel economy. Cruising at 40 turning 4,600 rpms seemed like running 5.88 gears in a car-real low. So now I look at a 17 pitch and it seems to be going backwards or am I missing something?
And question two, is there that much of a difference from alum to stainless? Thanks again

I find it hard to believe the boat only ran 40. I would think at least upper 40's but more like low 50's..

Dave

Well Dave unless somethings wrong with gps or tach thats what I have, 4,500 - 4,600 rpms and grs says 40.
I know nothing about this model boat so I dont even know what its capable of. I'm not looking for total top end cause I'll be pulling my kid on a tube at times and cruising around the rest of the time. But in my opinion 40 at that many rpms is not good for all around.

If you prop for 4600 you will expoerience the best cruise speeds the boat has to offer. If you prop for 5000 RPM at WAOT then you should experience the top end. The power band of your motor is 4600-5000. If you fall below 4600 then you would be lugging the motor, consuming a lot of fuel and taking life off of your motor. So if you were to go to a 21P then you would loose 400 RPM putting you at 4200 RPM which is NO GOOD! So to answer your quetion you should not go to a 21P Mirage Plus as you don't want to fall below the 4600 RPM at WOT.

Julie

Just a thought, make sure your GPS is set to MPH not Knots
40 knots = 46 MPH. And congrats on getting back in the game, maybe we'll see you on the river, happy boating

Yup, 17p Mirage plus...
300HP at the prop, 1.3 Alpha drive.
The boat should top out at 50mph.

okay I checked a few things today, engine is 454 330 hp, outdrive is geared 1.47 and is a rebuilt lower unit. Going to mess with it this week end I hope and write down all results. Thanks a bunch guys, Dave I hope to see ya on the river, gotta post some pics of this thing soon.

19p M+

See you on the River...:drink: