Re: 1968 Johnson 33hp RXEL 16R long to short shaft conversion
The conversion is easy, finding the parts may be the tough part.
Best bet is a well used "parts" motor. The motor will need to supply a short driveshaft, and possibly a lower shift rod.
To make the swap, just remove the lower unit as you would for doing a waterpump/impeller change.
Once removed, There are 4 basic changes that I can think of which need to be accomplished.
1) Remove the 5" extension housing from the exhaust housing - easy after the lower unit id off, just remove the extension piece.
2) Replace the long driveshaft with a short one (once the waterpump housing and impeller are off, I believe it just slides out of the gearcase) put a short one back in, and re-assemble the pump (do an impeller while you are there)
3) Shorten the water tube. If it already has a 5" extension piece on it, remove that, and you are done. If it is an original long shaft, just mark the tube EXACTLY 5" up, and cut it at the exact same angle as it has on the end.
I have seen/done both. I use a dremel with a small cutoff wheel to carefully cut the water tube shorter without removing it, i just cut it in place. measure twice, cut once.
4) Look at the shift coupler. Is it a small, short "standard" one, meaning there is a long lower shift rod? OR..they made a 5" long brass extension shift coupler (I have a couple here) if it IS the 5" shift extension coupler, swap it with the standard, small one, and that is it.
NOTE* if the shift coupler is already the short one, and not the 5" long one....you will need to get the short lower shift rod from your parts motor (the rod coming out of the lower unit gearcase) and swap them, although I have successfully cut the shift rod EXACTLY 5" shorter, used a rotary file to carefully make a new groove to hold the bolt in the shift coupler, and it worked out great (many hours on that motor, no issues)
I do know of people who have successfully had driveshafts shortened by reputable, knowledgeable and competent machine shops/welders who cut out 5" vee off the edges for good penetration, place the two pieces in "V" blocks,
first tack welding them, then checking runout, once perfectly straight, they proceed to weld with SS rod, and continue to check runout untli complete.
Another option, but if you can find a cheap parts short shaft parts motor, you will get you shaft, shift rod, and a pILE of other good parts...
