Is This As Fast As It'll Go?
 

I have a 1992 27ft Fountain, 700 HP, 540. It's been dyno-ed. Has an XR drive, 1.5 gears. It's making 700 HP at 5600 RPM's and 655 lbs of TRQ. This is as high as I can get it to spin up; 5600 RPM's with a Bravo 4 blade prop done by BBlades. The fastest I can get it to go is 80 MPH on the GPS in "perfect" conditions. Tried a 28 pitch prop Merc labbed 5300, 79 MPH on GPS, a 27 pitch Hydromotive labbed at 5500 RMP's which gave me 79 MPH on GPS. Also, tried another 26 pitched prop, labbed but not sure by who, 5700 RMP's gave me 80 MPH with too much stern lift so had BBlades do me a prop. Final result was 5600 RMP's and 80 MPH on GPS. Trimmed up to 4, tabs set the same, used a straight edge on tabs. If I lift them I don't gain anything. If I trim more, it seems to loose speed.

Just seems like it should go faster for the HP; maybe I'm wrong. Any advice is appreciated.

Thanks,
Todd

I had a 92/29 w/ twins (502's). 80 was max, and always faster w/ a 3 blade vs. a 4 blade. Is your XR set at the same height the original drive was? If so, add 1 pitch and get a Mirage +, 3 blade to improve top end.
Carder

Thanks for the input, Carder. I tried a 3 blade once before but it blew it out. Also, I'm pretty sure the new XR drive is set up the same height as the old drive. It's 5 1/2 X dimension.

BTW: nice boat! We boat up in Bay City also and saw you over Memorial Day Weekend. We have the fountain with the blue flames on it. :D

seems slow to me for 700 hp...

My '94 27 with a bolt on B&M 250 blower package, less HP than yours would run 83 GPS with a stock 27" Hydro prop.
Stock Bravo drive. 5800rpms

Thanks for the reply, US1 Fountain. This is a N/A engine. Don't know how much difference there is between that and a blower motor; I would imagine quite a bit. This engine actually makes 740 HP @ 6200 RPM's but I can't get it past 5600 and to get it to 6200 you would have to lab a 24 pitch which Brett @ Bblades said it would be wash and you'd loose cruise speed, etc. So not sure where that leaves me. Seems like a lot of wasted horse power.

~Todd

Was the dyno run done with the dyno shop headders of your marine exhaust? Full accesories and sea water pump, as it is in the boat? Can make a huge difference in the horsepower.

Just outta curiosity. What is the dyno HP at 5600 vs. the HP at 6200?

Hey Ragged Edge,

I was told it was run with marine headers (not mine) but with my C pump. Thanks.

~Todd

Hey Pachanga thanks for the reply. It made 700 HP @ 5600 & 655 TRQ and 740 HP @ 6200 & 637 TRQ. Engine was dynoed by Platium Designs out of Norwich, OH. Engine was built by Champion Performance out of Center Line, MI. Champion Performance is some of Sterling's old guys that parted off and opened their own shop. Great group.

~Todd