SKH

I am new to OSO and have had my 2003 heat (open bow mid cabin) for two years. great boat have few question on the drive. I am currently running a XR drive and top speed is 75 mph gps. Iam looking at putting a XR with a Sportmaster shorty would this increase MPH or am I just wasting money. XD is 18.25 prop I am currently running is a brovo 1 28P
Any help would be apprecated
Thanks Steve

FKNMKE

what size motor are you running? I have the same setup and getting 74 with the XR drive and a Bravo 28.

nedpoole

iTrader: (1)

IMO, you're wasting ur money at that speed level on the sportsmaster.

here's why...

the X dimension is already pretty high on the Heats. it's likely you will have a fair amount of prop blowout w/ a shorter drive.

there was another guy on here who upgraded his heat to a 525 EFI\Sportmaster XR setup and was not getting very good speed numbers until he swapped sportmaster lower for std XR lower.

it's pretty common to actually add length to the drive (spacer) for added stability and less slip w/ the step hull heats. esp around your MPH. my boat chine walked a bit at 75 w/ stock bravo 28 before adding the spacer

mine runs best of 83 and 80 all the time w/ Teague platinum XR (imco std length lower), 1" spacer and labbed 28p bravo prop.

what RPM are you at running 28p and 75 MPH? you might gain 1-2 couple MPH adding a 1" spacer and or labbing 28p (depending on your HP)

SKH

Thanks for the reply and the information. You saved me $6500.00 owner of the drive was definatly giving me some bad information.

I am running a 496 bored 40 over with a Pro charger machine shop est hp at about 700+-. I am turning 5000 g at 75 mph. I will order the spacer and I have an extra 28P labbed prop I can install with the spacer. I have seen 80 twice but it is usually when there was about two foot plus rollers.

Thanks,
Steve

Steve Zuckerman

Try the spacer first.
I am running (with a 19.25 XD) a standard length IMCO lower, a 1" spacer, and a 30" P-5X.

SKH

Thanks Steve,

Ordered the 1 " spacer from Imco yesterday great customer support. Should I not put the labbed 28P on or just stay with the standard 28P prop? Were is the best place to buy a 30" P-5X I Iwould like to give one a try?

Steve

sport

I have a 30p p5x that I do not use any more it looks like new if you are interested send me pm.

nedpoole

iTrader: (1)

i would just try the stock 28p and spacer first. less moving parts that way. if you lab and do spacer. tough to tell which one made the most improvement.

you should be pretty close to 80 w/ the spacer and your setup. esp if it's truly a 700HP setup. i think mine was only 600-650 last year.

Open bow might be slowing you down though. have you tried putting a hard cover on it? only boat i'm familiar with that had open bow was CB's... and it was wood free so it's a lighter layup than ours.

Bbeck

Nedpoole what hp are you currently running to see 80? I have a heat and am currently building a motor and it should be around 600-650 just curious on my propping and spacer step up as well

nedpoole

iTrader: (1)

my guesstimate was 600- 650. i never put it on a dyno

rebuilt Gen VI 502 mag w/ roller 525 EFI cam,
2.3L top mount whipple at 4psi
dana exhaust w/ dry to tip risers.

Teague platinum XR drive w/ 1" spacer and balanced 28p bravo 1 prop

however, urs is a 97 which means no step and lower X. i would suggest measuring your x dimension.
i bet you'll have to go up w/ a shortie rather than down w/ the spacer.