DPS-A weird behaviour

[saaristo]

Haven't done much hours on this boat of mine. So when you start noticing things you start noticing things :joyous:
According to the trim gauge the normal operating trim range is from -6 to +6, thats where the whole rpm range is under your right arm. Then comes the shallow water range and trailer position.
however, the water today was flat like a mirror so I tried to trim it up to reduce the drag but started noticing every time you go to plus side (from 0 to +6) a vibration appeared that could be felt through the hull plus it kinda went noisier. So what's that? When back at the marina (I have it wet slipped) I trim it down as far as it goes and saw that the trim cylinders are not fully retracted. To tell you the truth, I haven't paid attention if it has been always like that. Anyway, this is the lowest position it will go, leaving ~2 inches visible cylinder surface (sorry, the picture is made in the water). Is that normal or there is something to be tuned?

Myself I started wondering whether it could be that the gauge/sender unit trim range is somehow shifted from the physical position range? So that for example it should go lower physically so the current -6 is actually ~0, thus the current 0-6 range is actually way more...say 10...12 or so?
The transom shield is 3883772, drive unit 3883609 and transom angle 13 deg.
Any input on this is welcome.

 

[QBhoy]

These indications can go a little off accurate and need set up again.
But my worry is that if you are getting a vibration and a bad rumbling or knocking when trimming up...your UJ may be worn.

 

[saaristo]

These indications can go a little off accurate and need set up again.
But my worry is that if you are getting a vibration and a bad rumbling or knocking when trimming up...your UJ may be worn.

That's exactly my worry. Just that for a joint there's no difference whether it is "bent" downwards or upwards the vibration and noise should appear both ways. Now however if driven on minus side of the scale everything is smooth and quiet but on the same rate plus side it's vibrating. That and the way cylinders look gets me thinking that maybe the drive unit should go further down thus meaning the current -6 could be actually around center position.

 

[Scott Danforth]

pull the boat
pull the drive
inspect the gimble and u-joints
inspect the alignment
then adjust the trim sensor
then put boat back in water.

 

[muc]

The picture you posted is a drive all the way down. The cylinders don’t retract anymore then that.

On a duo-prop, because the rear prop is so far back. They tend to ventilate (suck air from the surface) if trimmed to high when underway at high speeds. Is it possible this is what you feel?

A good test for ujoints and gimbal bearing in the water. Run the boat at 1500 RPM out on the water trimmed down. Driving straight. Now slowly turn the steering wheel and listen/ feel for vibration as you get near full turn. If it changes a lot, you may have bad ujoints or gimbal bearing. If it doesn’t, they are fine.

 

[BRICH1260]

By the picture things look fine. That's just how they are.