Mismatched driveshafts

A repair job is never allowed to go by the book. There always - always - has to be some weird, poorly documented catch that sets the whole thing back.

This time, it's driveshaft splines.

The new lower unit for our damaged Johnson 30 is here, courtesy of J&J marine (Hagersville, ON) with quite a bit of help from family and friends to deliver the thing.

The mounting flange is compatible and the new gearcase is nearly identical to the old. There are a couple of minor differences- the new one has a reinforced skeg tip and a slightly extended anti-spray plate above the anti-ventilation plate. There is also one very major difference.

The new one came with a vertical driveshaft for an S (15") leg, while our engine - like most 30s - has an L (20") leg, so the shaft has to be switched out. This is, normally, an easy one-minute task. Our new gearcase, though, is incompatible with the old shaft. From the water pump down, the L and S vertical shafts should be identical; clearly, they are not.

Our new lower unit was made in 2000; it appears that there were some slight changes to the pinion and its bearings between '95-'96 that render the two driveshafts incompatible (although the new lower units still mate with the old midsections, and vice versa, if the shaft matches the lower unit). We now have to either find an L-size shaft with the new spline on the lower end, have the old shaft machined to the new spline shape, or exchange the new gearcase for one that fits the existing vertical shaft.

So much for getting back out on the water this month....



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