Need Help - Have 03 38' Fountain Lightning Staggered - Merc 575's w/Chillers, AZ Speed ECU's (rev limiter set at 5650-5700), Aeromotive fuel pump, Imco lower (1.50 ratio) - standard length - I have tried 3 different props: I am thinking about trying 5 blades - Hydromotive P5 or Merc Maximus - or getting 34 Bravo labbed.

My 2 ?'s are which 5 Blades and how much harder on lower units are 5 blades over 4 blade Bravo

My friend runs identical boat & power less shore power (AC, Battery charger), -1 Imco Lowers (1.36 gears), Hydromotive P5 stock 5Blade - 30' pitch - 97 mph - 1 person - 1/2 tank, spring time (70' temp)

GPS Speeds are mid July - 90+ degrees, 2 people 3/4+ tank of fuel

34 Bravo - stock w/ring cut off - 92 mph - 5100-5200 rpms
32 Bravo - stock - 89 mph- 5400 rmps
32 Bravo - Labbed - 92 mph - 5600+ - all over rev limiter
-32's just seem to run out of momentum around 87-88 mph

The 34 Bravo handles 10x better in midrange - I am either going to lab 34 Bravos -to get rpms and top speed up or get 5 blades. My friends boat seems to ride much looser w/-1 Imco lowers and P5's than my boat. Why is this?

Per conversation w/Hydromotive - thought I should get P5 30 pitch to get my rpms up close to 5600 -

Any suggestion's on P5 vs. Maximus and what pitch - Should I have Lab or leave stock?

I know if I went with -1 or -2 Imco lower I would pick up speed but with my stock Imco lower what will be best setup and not damage lower unit.

I feel this boat is capable of high 95+ - anybody with same setup or close?


Bryan

Bryan, Your speeds rock. On our 35' 600 N/A, we are getting 88 on 30 CNCs and 85 on Hydro P5's, and 87 on QIV's 29p hitting the rev limiters @ 5600. The P5's raised the transom too much, consider QIV's around 34p, or CNC's @ 35p for starters. If you try stock prop it will at least give you a baseline number... easy to improve on. Carder

You don't go full throtle all the time try a 30 pitch maximus you will love the hole shot, midrange punch and GPH at cruse with the same top speed or a few more.

Reggie is correct. There are a number of great choices out there that will improve where you are now. Carder

Carder - you really tried a number of props. Did you try out the P5Xs? Who's cnc'ed props did you try?

i have a client who runs the same set up. from what i read the only difference is he has i.t.s gimbal's. and his ratio is 1:36 a we run an imco lower with modified intake's.
with time spent dialing using spacer's and trying prop's we ended up with hydro p5's and a spacer.the boat on it's best day ran 109.2, 3 people 1/2 tank fuel.

do you know how much power the engines make . and where does the prop shaft fall at neutral trim in reference to the bottom as far as above or below?

Rebel, did not try any P5X's... sent you an email on what we did. Carder

Thanks for the reply's - do you know how much power the engines make ( estimated 650-675). and where does the prop shaft fall at neutral trim in reference to the bottom as far as above or below? (I will have to check to see on where my prop shaft is compared to bottom of boat) Boat feels very tight to H20 compared to my friends 38 w/-1 Imco lowers, I would guess same height as with stock XR drives since my Imco's are standard length. What advantage would spacer's do for me?

Bryan

spacers will help in drive height. i was assuming you had shorties . the spacers would be key in finding and dialing in the proper height for your application.
theoreticly you would want a higher prop shaft height as you increased speed of your boat, in essence surfacing the drive or bringing it closer to the surface.
the set up i was refering to has its gimbals with -2 inch shorty imco's and a spacer, since the imcos dont come in 1/2 inch increments.

Found out my engines are putting out more like 625HP. My x dimension is 19 1/2 with the standard length Imco drive. Looks like I am going to try 30' P5's in spring or try to find some used -1 Imco's housing's.