You are on the right track.

The assist cyl and shuttle valve on some volvo SX units did this.

If it's still under warranty then Volvo will cover the repairs.

While the drive is shaking, try turning the wheel, if it goes away, then you
have a bad assist cyl.

This condition doesn't really hurt anything. I guess if it goes on for a
long time You will cause exsessive wear in some components.

What is happenings is, and you can watch it happen, is the shuttle Valve and
assist cyl are working against each other. They act just like a steam
engine.

For all you Mercruiser fans, this first showed up in the late 80s on power
assisted sterndrives and migrated to all the other brands.

Good luck,

Carl G. Craver



(Strange name for someone who doesn't work on outboards anymore...LOL)

"Mike V." wrote in message
m...
I have a 25 ft. Larson with a 5.7 LT engine and a Volvo model SX
outdrive. We like to pull into our favorite anchorage spot were the
water depth is around 3 to 4 feet. When pulling in I trim the outdrive
way up and proceed in slowly. When I start the engine to leave the
outdrive shakes back and forth until I got out to deeper water and I
trim it back down. Any ideas on what may cause this? I was thinking
about changing the power steering servo unit. It seems strange that it
doesn't shake when I trim up only when I start with the outdrive
already in the up position.