I'm looking at a 1999 353 Fastech that has HP500's mated to std Bravo 1's that are mounted on extention boxes. Are these more prone to problems than those w/o the boxes and is there anything in particular that I should be checking? I've never had a boat with boxes and heard they are harder to dock for some reason. Thanks for any info.

If they're Stellings boxes, there's a a couple of u-joints,
the slip joint and the carrier bearing that require periodic
greasing.

Are they harder on the drive ??...they don't use
the rubber coupler that they have in a standard application,
but, I 've seen alot of boats with them that never have had
a drive problem, unfortunately, I'm not one of them.

I don't place all the blame on the boxes though.

I've never heard of any docking isues, thats more
related to prop rotation.

Yes, I think they are Stellings and as far as I know the rotation is stock spinning out. Never drove a boat with boxes but some sales guy at a different marina was giving me a laundry list of how bad they are for docking. Maybe he was confused with staggered setup where the 2 drives are closer? At any rate, can I expect any realistic MPH gain with these on a 35 Fastec? Also, I believe these are std B1's 1.5 with 30P Merc SS 4 blade. if I wanted to upgrade to XR's and or Sportmaster lowers do the boxes present any issues? Thanks.

STellings boxes will raise your prop dim aboout 7/8" in the neutral position which is the top hole and can be adjusted to raise 3" in the bottom hole. The boat will handle like a longer boat at the dock and on the water. At the dock, just remember that they are back there sticking out. You might see a problem with cavitation out of the hole until the props get a bite depending where the boxes are set. I am running mine with the rubber couplers but it got a little complicated with which parts to use. Drive line bell housings etc. Without the rubber couplers there is a drive saver piece that is available that supposedly reduces the shock to the drives during shifting but I didn't like the looks of it and went the rubber way since I had the parts on the shelf. Changing to different drives later won't be a problem. Any Bravo replacement drive will bolt right on. Alignment issues are not a problem since shafts are used. Make sure the shafts are phased correctly. I hope that helps?

Thanks for the info the main concern at this point is what to check them for when we do the survey. I don't think the seller is going to want us unbolting the drives but I'm figuring we'll at least do a pressure test to make sure the seals are ok. If the oil is clean and there is no shift problems we should be ok for a bit.

if you up grade to xr drives sports are shorter and you might pick up speed, also Mr. Gagets on here can do a better upgrade on your drives over the winter and put on imco shorties which is a faster lower case than the merc sports. good luck I got a box to try out as soon as my motor shows up

I had bravo extension boxes on my 32 AT. Boxes alone should NOT cause the boat to be more difficult in docking situations---at least not based on my experiences with them on my boat.

The only situation I could see being difficult for docking would be a "staggard" engine/drive set up where the drives are mounted closer together.