Originally Posted by
champ20B
Coupling shafts can be tricky. They need "perfect" alignment and strength along with balance, otherwise such a fabrication can be destructive to the gear-case and power-head and dangerous.
Your very best bet cost wise is to cut the shaft to height you want, then have a reputable machine shop cut the necessary splines you need. It is a relatively simple process and really shouldn't be too costly. Whatever the price is, it will be worth it to be put together right and solid.
It is neither required nor necessary to put a solid connection between the power head and lower unit. Countless MOD and PRO motors over the years have run for years without such a connection at up to twice and over the RPM that would be encountered in this type application.
What is absolutely necessary and required is that the mounting surface of both the lower unit and power head be square and parallel with each other. I concur with the square drive shaft coupler idea and they can be purchased a lot of different places, or even made as described. The slight "sloppiness" is even desirable, if the power head and lower unit are not exactly in line square and parallel with each other as can sometimes be the case with a fabricated tower housing that is not constructed with the proper techniques.
If you want to spend extra money, that is your prerogative, but if using a factory mid/housing mis-alignment should not be a problem unless the housing has been welded on and consequently warped from the heat. That could be solved by placing in a mill of sufficient height and facing the top and bottom surfaces of same just enough to get an even cut on both surfaces. This is best done prior to cutting the drive shaft and assembling with the various couplers.
GOOD LUCK
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