Volvo Penta Auto Trim Not functioning (?)

[herbk@comcast.net]

Hello:
Just launched the 2020 R-5 this season and noticed the boat "porpoising" quite badly when I get up on plane. I also noticed the boat speed is
down from last year at the corresponding RPM.

Engine is 300 HP Volvo DuoProp.
I have Auto Trim activated and the trim gauge on the screen seems correct: at least, where I would expect it to be for the given speeds and turn conditions. And it moves from 0 to about 19 degrees (on full plane) just as normal.

Nevertheless, I deactivated the Auto Trim and was able to resolve the severe porpoising by manually trimming the outdrive. I don't know about the speed to RPM ratio yet as I was done for the day. But the gauge reading seems to be accurate under manual, just as it seemed to be under Auto Trim.

Odd behavior and was wondering if anyone has had a similar issue with Auto Trim and the gauge response?
Herb

[herbk@comcast.net]

Since this post has had an abundance of views and no reply’s, I am assuming that I may have this all wrong and need to look in another direction for this new (2025) issue of porpoising.
In reviewing all of the reasons why this occurs, I can rule out boat weight distribution (loading) since nothing has changed since last season when this was no issue.
I am thinking the dealer had the outdrive off this year for servicing, so two possibilities may remain:
1) The outdrive unit was remounted higher (or lower) on the transom by accident.
2) The props were removed and replaced with different ones, again by accident.

Is the 1st even possible? Are there multiple mounting locations on the stern drive (like on an outboard) or is this absolutely fixed, single location, not possible?
Then, the props: wrong set or slightly damaged set?
The trim appears to be working fine. Also, the trim tabs retract and seem fully functional so I am not looking at that.

Any thoughts would be appreciated

[Cctvdc]

You are correct that the outdrive cannot be mounted in a different position. They are bolted to a housing on the boat and only controlled up or down by your trim. I cannot speak on props not that familiar with that. Others on this site will speak on that I’m sure.

[herbk@comcast.net]

Is it possible this is merely a “calibration” issue?
I am not the mechanic but I am sure they removed the outdrive as part of servicing this year.
Does attention have to be paid to “rehanging” the drive and is there a “sensor” that needs to be “zero” or calibrated in some way?
I noticed today that under auto trim and full planning at speed, the same reading of 19 degrees from previous years but the boat was porpoising. When I “trimmed back” manually to 16 degrees on the gauge, all seemed well and the boat “felt right” again.

Just wondering…..
Breakaway
2020 R-5
300 HP Volvo Penta DuoProp

[FirstStar]

My VP R5 auto trim seems to go up in 5 degree increments. I've rarely seen it above 10, maybe once at 15. At 19 degrees, and a light bow load would certainly cause the conditions you mentioned.

[herbk@comcast.net]

I maybe on to something here:(?)
At least I can tell what the default settings are.
Found in the manual download from the Volvo Penta support website. Must have boats serial number to access.

“PTA Calibration
PTA (Power Trim Assistant) automatically adjusts the
trim angle to boat speed. The system has a basic
setting, but it is possible to set five different angles for
five different speeds.
On boats with more than one station and with several
displays it is enough to do the calibration on one
display for it to be shown at all stations and on all
displays.
For installations with several engines the calibration
needs to be made for each engine
1 Navigate from the settings menu to PTA
Calibration. Press to get to the submenu.
2 Use Pos 1.
to set the trim angle for idle, PTA
Press to confirm the setting.
3 Proceed to PTA Pos 2.
Use to set the rpm.
Press to confirm the setting.
4 Use to set the trim angle.
Press to confirm the setting.
5 Repeat steps 4 to 5 for Pos 3, Pos 4 and Pos 5.
6 To return to basic settings, select Defaults and
press to confirm return to basic settings.”

[herbk@comcast.net]

When I returned to the lift, the trim position on the Garmin was zero and the EVC was -5. However, with the boat elevated, it was visibly obvious the outdrive was still “trimmed out” a bit, not tucked in as you would expect in “idle”.
I trimmed manually all the way in and the EVC went to -7. I then followed up with a “return to default”. Going out now to check any results or changes. If not, I will be back to the old days with no PTA.

[herbk@comcast.net]

Looks like more work to do to have a functioning PTA available to my 2020 R-5.
The “return to default” sequence did not seem to return the settings from last year, before the outdrive was removed for maintenance and then reinstalled. And while I have a “functioning” trim switch and apparent tracking position tracking thru the EVC, the trim position on the Garmin screen is not reading correctly at all. It pretty much is at zero thru the usable boating range.

At one point in an older post, someone had asked if anyone could check the positions 1 - 5 on their EVC so they could replicate on their boat and reset them. I don’t believe I ever saw a response so I will need to contact Cobalt to see what they say about the default positions for 1 - 5 and duplicate those settings.

So the season continues on our R-5 but without the luxury of the PTA feature.

[stifflkd]

Don't chase the difference between what the EVC reports and that of the Garmin. The Garmin reports % from max trim down to max trim up. The EVC reports degrees from vertical.