I have used both the drive saver and the aqua drive systems on my boats.
Both work well, the drive saver does result in a need to ensure the bore alignment is maintained. I used a dial indicator on the prop shaft during installation
to make sure the shaft was centered.
The big advantage vs being directly coupled is if you have a longer prop shaft the movement of the engine
at sea causes less vibration.
Definitely carry coupling bolts and nuts in case something goes wrong.
This was on a 4-107 with a v-drive
The new boat has an aqua drive system and it is vibration free. The units are not maintenence free, they do need rebuilt on a schedule, in my case it was easier to replace the CV joint and the thrust bearing.
What is nice is that the transmission
does not see any forward and aft loads as these loads are carried on the thrust bearing soft mounted to a hard point on the boat.
This allows much softer motor
mounts and less vibration.
The aqua drive unit is on a 90 hp Perkins
driving a 55 foot sailboat.
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