Reply To: Shaking at High RPM Running 1955 Evinrude Fleetwin Aquasonic 7.5HP

[Don]

Well, I do remember there was some sort of change made in 1956 in the rear seal hsg, not sure if the props changed also….
The good news here is that a replacement gearcase solved the issue, without doing a lot of investigation/replacement work on the original gearcase….
Perhaps the shock spring was actually broken allowing the two driveshaft halves to spin independently. The vibration may have just been a result of the spring pieces chattering around in there…
Perhaps the gear housing was actually bent/distorted, who knows…
Just be sure to mark this gearcase so you or someone else doesn’t accidentally use it in the future….
Although it is tempting to rip the darn thing apart to figure things out, just be sure to toss the parts away!