That's a quick and easy test to verify. Is that an Imco SC lower?

Keep in mind, Bravo props are figured to run 1 pitch smaller than stamped....

First off, I changed the lower unit to the 1.5 ratio off my stock "x" drive and put it on my XR instead of the 1.35 Imco lower I've been running

So, if an "XZ" drive is an x upper with an xr lower, what would THIS be ? an RX ? lol

https://cimg6.ibsrv.net/gimg/www.off...e2affafa66.jpg

It was ROUGH and BUSY on the lake today.. getting numbers was difficult so not as complete as before.....

SO... Spinning a Bravo 30 1.5 Ratio stock lower...

40 MPH @ 3000 RPM trim 1
48 MPH @ 3500 RPM trim 2
57 MPH @ 4000 RPM trim 5
94.7 MPH @ 6085 RPM trim 6.5 (pulled out of the throttle)

Boat ran good on the pad. bow seemed to carry pretty good overall...

Bravo 34 LH (By the way.. the boat comes off the trailer WAY easier if you put the shifter in forward when backing up with a LH prop LOL)

45 MPH @ 3000 RPM
56 MPH @ 3500 RPM
65 MPH @ 4000 RPM
93 MPH @ 5500 RPM (couldn't get any more RPM out of it )


I'd try to find a 32 but that'll likely just get me to 99 mph which is where I've been stuck at anyways.....

Thinking maybe a -1 shorty and go back to 5 blade props ?

-2 shorty with 1" spacer installed and ready for testing.. :evilb:
Went back to the 1.35:1 ratio.. the 1.5 didn't show much of an advantage and 1.35:1 is SUPPOSED to be stronger anyways...



https://cimg7.ibsrv.net/gimg/www.off...528986ca1d.jpg

Pullin for ya to hit that magic number... Good Luck!!!

https://www.offshoreonly.com/forums/...-outdrive.html

Looking forward to your results. I considered a shorty when I first bought the VR1. Always wondered about how it would run. On my 21 Challenger a 2.5" shorty Alpha SS netted 5 mph & 500rpms with no prop change vs before. The shorty resulted in a propshaft 3.5" below hull, which is what my VR1 is with a stock Bravo lower. Keep us updated!!

So... They shorty did not help..

I first tried the 26 p5x I've been running.. Drive trim had little effect on the attitude of the boat now. Trimming above neutral would create a rooster tail instead of lifting the bow.
Prop slip was about the same through the midrange but went up a little on the top end.. lost 3 MPH for 96 MPH @ 6000 RPM..

Tried a bigger prop (28 P5X) midrange numbers looked promising. (76MPH @ 4500 RPM :) )..
boat accelerated decent but could only spin it 5200 RPM @ 92 mph..

So, once again, it looks like I need a prop in between the two I have.. LOL

InsaneMan: Didn't you raise the X when you redid the transom ? Or was that the last boat ?

That was the last boat.. A 26' Corsa ended up with the prop shaft 3.25" below the bottom and worked well..

This one was at 3.5" below from the Factory and I went to 2.5" below. may work with a 6 blade prop but don't really want to go there..

NEXT !


I picked up an HD transom assembly.. Puts me one step closer to an SCX upper..
and should prolly be running one anyways with the power and speed I'm at..

https://cimg3.ibsrv.net/gimg/www.off...6930ada45d.jpg


I ALSO Picked up an Imco extension box.. :D
Seems a 12" box and a -2 shorty works well on this hull ... I'm going to find out....

https://cimg1.ibsrv.net/gimg/www.off...73c3e3486c.jpg

You may want to check with George at All American Drive before you spend money for SCX. I had him go through my drive and rebuild it, he gives a 24 month warranty. I have a 280 with an old Bravo drive at stock height that runs pretty good. I had a B1 4 blade 28P labbed by BBlades and it only made it worse. Porpoises like crazy, determined the prop now has to much rake. I had an old Hydromotive QIV 27P without a bell, tough to keep on plane with a load in rough water, but it likes speed. I have to go easy on the throttle up to half and wait for the nose to start coming down and then I hit the trim and hammer down. I was in 1.5' waves so had to go easy on the trim, had to keep the boat flat to the water, but it ran great, just a slight bit of chine walk that was easy to sort out. I'm running an NA 524 and I hit 85 before things got to rough. I know I need a lot more pitch as I hit my 6k rev limiter pretty easy when the water is calm. My next prop will be a Hydromotive no question, will try a 30P next summer. No question the B1 is more efficient at low speeds, I think a QIV with a little bell will help that. But the way the QIV runs above 60 is night and day different.