Unfortunately, the AQ series drive old timers have since retired.... and the new young guys don't want to learn the AQ series drives.
What a shame, because they are out there in numbers, and will remain for years to come.
And in many respects, they are much better designed than the drives that followed.
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While on the trailer, and while going into reverse, there is no reverse prop thrust to pull the drive AFT and UP... smacking it into the rubber bumper.
While in the water there is plenty of thrust to give the drive the "Jump Start" as you put it.... and that is exactly what's happening.
This thrust quickly takes up the slack between the latch unit and the set pin.
When it does, your latch hooks are releasing from the set pin.
They should not release.
Something is wrong with the profile of the latch hooks, or the set pin, or perhaps even the geometry of the drive has changed due to worn bushings, etc. or even an incorrect assembly by the last person in there.
You may want to look into this.
Another common cause, would be if the vice rod (the plunger as you called it) is not fully retracting after the drive has been lowered.
If not retracted, it may be holding the release rod down, which in turn gives the latch hooks more releasing advantage with the "Jump Start" mentioned.
The screw that the mechanic is adjusting (which is actually a thrust sleeve) will only cause a change to the push rod from the vice rod pressure plate contact.
However, the push rod must fully allow the latch hooks to return to their highest position in order to latch onto the set pin.
Make darn sure that the little single center lift spring is good and strong!
By adjusting downward on the thrust sleeve, the push rod can return to a higher position ensuring latch hook contact with the set pin.
By adjusting upwards on the thrust sleeve, we ensure vice rod contact and drive tilt-up release function......,
but we may pay a penalty the other way.
The adjustment is simple.... but it must allow the rod to function in both scenarios.
Common issue.
The bore in the suspension fork is not deep enough for the adjusting lock nut to travel
upwards far enough.
With the push rod removed, increase the depth of this relief so that the locking nut can raise higher up into the suspension fork.
IOW, make it so that the nut can raise up further, thus raising the latch hooks, yet still have the correct thrust sleeve height.
A cheater test for this would be to adjust the thrust sleeve, but take the locking nut and run it way down.
Now the push rod can raise up higher within the suspension fork, while no longer being limited by the undersized relief.
I don't know if you can access and view this, as you may need to be a member.
I have put together an entire thread dedicated to the AQ series Volvo Penta drives here.
http://www.baylinerownersclub.org/f...82-Volvo-Penta-AQ-series-frequent-Q-s-amp-A-s
Go to the link titled Reverse Latch questions.
Is your idle RPM within specs?
Can you post a few good photos of the entire latch unit?
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