I ignorantly bought a used lower unit from a guy who said 'they're all the same' but when I got home and compared them, I found the upper drive shaft is a little shorter than mine, maybe 1/4" to 3/8". However, mine is currently just loosely reassembled, so I don't know for sure what the actual properly installed length would be. Otherwise, the two units look and measure out to be pretty much the same.
The short question for any experts who already know the answer is, is it ok to use it, even if it's short?
More info to help figure it out, if needed:
The splines on mine are 1" long, his are 1-1/2" long. I don't know if there's an upper seal that might get mangled by the longer splines, even if the shaft length is ok.
*If* it the shaft length actually nets out to a 25% reduction in spline contact, I've seen posts of snapped drive shafts, it seems like I might also risk mauling the crank splines in a catastrophic event, like the LU seizing. I really have no idea of the condition of this other LU is, other than the guy claimed it passed pressure testing. Hate to ruin the engine on an experiment.
Also, I'm curious what this thing is. The parts diagrams say the '78-'91 non-90deg V4's use an upper shaft that's 7/16" shorter than the '92 and newer ones but it doesn't say what the net difference in installed length is. They also say they use different lower shafts, so I suppose the net result could be the same installed length, or close enough. If anyone has a thought on this, it might help me decide whether to dismantle this one and use the parts to rebuild mine instead of trying it as is.
Thanks in advance for any guidance. Got to... get back... on the........ water............
Matthew
The short question for any experts who already know the answer is, is it ok to use it, even if it's short?
More info to help figure it out, if needed:
The splines on mine are 1" long, his are 1-1/2" long. I don't know if there's an upper seal that might get mangled by the longer splines, even if the shaft length is ok.
*If* it the shaft length actually nets out to a 25% reduction in spline contact, I've seen posts of snapped drive shafts, it seems like I might also risk mauling the crank splines in a catastrophic event, like the LU seizing. I really have no idea of the condition of this other LU is, other than the guy claimed it passed pressure testing. Hate to ruin the engine on an experiment.
Also, I'm curious what this thing is. The parts diagrams say the '78-'91 non-90deg V4's use an upper shaft that's 7/16" shorter than the '92 and newer ones but it doesn't say what the net difference in installed length is. They also say they use different lower shafts, so I suppose the net result could be the same installed length, or close enough. If anyone has a thought on this, it might help me decide whether to dismantle this one and use the parts to rebuild mine instead of trying it as is.
Thanks in advance for any guidance. Got to... get back... on the........ water............
Matthew
