Rob so you had herring cut the diffuser ring and weld in a straight 3 in extension or a flared 3in extension?

I too wonder if standard a sportmaster or Imco lower on a 388 with 600sci and ITS would be worth it over the standard XR lover?
Dean

Can anyone give us any insight?

im running imco boxes with 1.5 xr upper and standard lower with nose cones, turning out and spinning 30p 4 blades at 5800 ive seen 101-102 gps, BUT this thing eats drives, so im goin to bmax 1.3. not sure if i should go with -2 lowers because of the boxes or not, i figure its a good place to start and i could allways ad spacers back in, if not. hoping to pick back up some of the lost mph because of the bmax's

I know it's been a few years, but our 388's haven't changed, nor has our quest to dial them in. I went off the above advice from P-Rob and installed 1" spacers on my 2000 388 with whippled 500's. IMCO standard length lowers. I'm guessing it's the additional bow lift/leverage that helps. No extension boxes. I have both labbed p5-x's and labbed bravo's to try with this combo. Appears I have the factory X of 18.5-18.75". Full cabin. I will try to post some results of the spacers, it makes sense because shorties definitely do not work on our boats.
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I have read through this thread, but still have a question or two. Hopefully someone here will chime in. I'm in the process of repowering a '99 388 poker run and considering installing 12" imco boxes I have access to. Right now I have HP500s and bravo outdrives. My questions are, if I use the standoffs and the bravo drives what should I expect? I know there are better options, but I'm trying to make use of the outdrives I have for now with the thought I could upgrade in the future. Also any idea on prop pitch for this setup? Any guidance or personal history would be greatly appreciated.

Any more info on this?

Were you running the 500EFI intake?

Not really anything yet. I will say the boat likes the P5-X props much better than the bravo 4 blades. 1" spacers are still on....

Nice thread. I do not have a hustler. But my boat is 41ft. At higher speeds it flattens out. My drives are 3.5 inches below the deadrise. B blades told me adding drive spacers would give me more bow lift. The 5 blade would give stern lift unless it was cut and modified. I have 1 inch drive spacers I'm going to install in the spring. They also have there 4 speed prop. Which is supposed to add bow lift. They said I can try them for 55 bucks a piece and can run them for 15 days. Undamaged of course. I just got this running and haven't checked to see if there is any water in the holing tanks. But I agree that on the heavier boat sinking the the drive will create more bow lift and reduce wetted surface. That and possibly having the rearward section of the bottom messaged some.