I put my 1" Drive spacer on today. Install was easy. Gotta work Sunday so I won't be able to test till Monday. 28 Heat 525efi xr w/its 28 bravo with added cup. Can't wait.

I'm sure you'll love it, be sure and post your results.

Why Certainly Moe

Well here it is
Gaffrig GPS speedo

At 2500rpm went from 25mph to 32mph
At 3000rpm went from 35mph to 41mph
At 4000 rpm went from 50mph to 60mph
At 5200 rpm went from 76mph to 78mph

At full throttle and trimmed way out I rarely hit the rev limiter. Prior to spacer I hit the rev limiter all the time.
So - It seems as if the low and mid range rpms had the most speed gains and only a minor speed gain at wide open. Not bad for only spending a few hundred $. Now I'm wondering if a prop swap is in need. What do you guys think. Keep in mind that todays conditions were a bit different than my original testing days conditions. Also keep in mind that I'm at sea level and salt water (Long Island).
(525efi 1.50 gears-its/xr drive-28 bravo with added cupping)

Ray

Yep, those numbers sound about like mine, although I saw a 4 MPH gain at WOT. I went from 83 to 87. Same location, same day.

Bob

Please refresh my memory
What Power do you have?

I'd have to say, money very well spent

Ray, I'm running a 28 Midcabin with ITS/XR. Whipplecharged 555 EFI engine with 5 PSI boost, Approximately 750 HP. Fresh water, 700' elevation and hot as h$ll. With a 29" lab finished Hydro P5X I'm running consistent 88-89 MPH @ 5600.

Nice

I'm considering a whipple
But I can't bring myself to terms with messing with a motor that runs everytime I turn the key. Also not a good resale with a modified motor.

If I understand it correctly, it's a very expensive project on that motor as well