kidturbo

Text me his number if you have it. The ones F-2 posted, look to be new model M6 bolt pattern. Transom assembles we have are older pattern.

Unlimited jd

iTrader: (5)

When I spoke with him, they were the old style

delsol

I was unaware that there was new and old style bolt patterns...when did that happen ?

kidturbo

I've learned more on the subject than I ever wanted to know D.. Seriously only learned of it myself couple weeks back.
When they changed the labeling to M6 is what I was told. Bottom holes only I guess. That template above has both patterns.
Check out the boxes F-2 linked. Those look to have both pattern on the drive side, but the transom side is totally new to me. 6 bolts on sides, one top, and one bottom.

kidturbo

Finished mock up of a 6 and extension box today. Broke out the laser level and digital angle indicator one more time to see how things line up. Left the port drive alone to get a good comparison on new vs old shaft height. With the 2" spacer in the lower unit, these set 3-3/4" lower than our current config. These extension boxes have two sets of holes, about 1" apart. We used the upper holes today. So on paper they would end up about 3/4" lower than we are now if we used the lower holes and removed the spacer. With the prop leading edge distance from transom being almost identical between both sets.

However the driveline angle with these boxes is no good. If ya look back to first few posts, we set up all the powertrain with a 3.5deg down angle. This followed through to the drives.While it helped clearance on the oil pans, and sets the crankshaft centerline dead level at cruising speed, It also raised the prop height a couple inches from stock. The boat feels great, very stable at 80mph. But if ya know anything about drive shafts, then ya understand both end flanges need to be within about 1deg to insure no vibration. So while from the outside everything looked good today, when I checked the angle on the #6 driveshaft flange, it was setting at 0.5deg. Leaving 3deg difference between the two ends. Which will ultimately lead to vibrations and failure..

Looks like I'm gonna build some custom extension boxes, again..

kidturbo

Looking for a #6 transom plate file in DXF or STEP if anyone has or knows where to download it. I actually have the bolt pattern from modifying the last set, but need one with #6 outside dimensions to match up these new boxes.

payuppsucker

Wouldn’t a wedge be just as effective?
(and easier to fabricate)

kidturbo

Well I looked at a #6 wedge plate install yesterday, and the matching offset washers on the studs. Looked interesting, if ya don't minding hogging out the holes in the transom. Just two issues. It wasn't on extension boxes, and the owner couldn't remember how many deg it actually gained him. I didn't have the angle indicator with me to check it either. I doubt it was 3deg however.

But my math says for prices of wedge plates, I could just modify these extension boxes as we did last time. It's actually pretty simple when your buddy has an old Bridgeport mill in the garage. But for the going price on used #6 boxes, I can waterjet 4 end plates and roll my own for about half. Think we only had $200 a piece in the 5 hole pattern end plates I did. Unless Aluminum has gone sky high since I last checked.

kidturbo

My favorite thing about this thread, on days like today, I can easily search and find all my notes from 4 1/2 years ago, rather than dig through a pile of papers...


How to build and brace extension boxes? Exactly where I left it..
Post # 54

Post # 58

Post #65 on estimated boat speed calculations with 17" 35 pitch props is pretty cool find also. HooDoo, those 34's been Slippen as I suspected. We should have been running 100mph at 4000R's the other day.

pasquesi

How about an update on this???LMAO!!!