Volvo DP-A hydraulics and SeaFoam

Does anyone have any experience using SeaFoam Trans-tune to clean outdrive hydraulics? It says it's not a stop-leak, but it's supposed to clean hydraulic valves and is compatible with all hydraulic systems. I've recently bought this boat (Cobalt 21 with VP DP-A outdrive) and have only had it out on a couple of short outings, but I've been working on the trailer and noticed the outdrive will drift down after a few hours. My thought was to try the trans-tune, cycle the hydraulics several times, and then flush it all out and replace with new ATF fluid. Do you think this is a waste of time? If so, how concerned should I be about the pressure loss? I don't see any external leaks.

Thanks

Re: Volvo DP-A hydraulics and SeaFoam

There is a diagnostic chart in the Volvo manual that describes a few scenarios for your problem.

Does your drive creep up in reverse?

Re: Volvo DP-A hydraulics and SeaFoam

Not that I've noticed, but I've only had the boat for a short time. I've read through the drive workshop manual a couple of times, but I didn't see much diagnostic information. Is that the manual you are referring to? I've only had the boat on the water twice and less than 30 minutes each time, but I didn't run it in reverse very much.

Is it normal for the drive to creep down when it's not in the full up (trailered) position? Since I've been mostly working on the boat and trailer in my shop, I have tended to leave it only about half-way raised.

Thanks

Re: Volvo DP-A hydraulics and SeaFoam

Is it normal for the drive to creep down when it's not in the full up (trailered) position?

Click to expand...

Nope,... It should Stay wherever it's left at....

Re: Volvo DP-A hydraulics and SeaFoam

I thought so, but just making sure. I guess I might start by cleaning the hydraulics with SeaFoam, flushing, and renewing the ATF and see if the problem continues.

I've searched the forum for this problem, and I've seen it a few times. Seems like the likely suspect is the pump rather than the lift cylinders. I wonder in fact if both of the cylinders would have to be leaking before the drive could creep?

According to the Volvo workshop manual, I think the pump valves have to be replaced as a unit (apparently the entire pump assembly). This may also mean that the individual valves cannot be serviced, but the drawings only show part numbers for the complete pump assembly.

Thanks

Re: Volvo DP-A hydraulics and SeaFoam

I am looking at the real factory Volvo workshop manual.

Re: Volvo DP-A hydraulics and SeaFoam

As a follow-up, I finished replacing my raw water hose and connector, regreased the u-joints, and replaced the outdrive oil. Afterward, I noticed the outdrive is no longer drifting down. I hadn't gotten around to trying the SeaFoam, so I'll just wait and see if it continues to behave. I had to raise and lower the drive several times through all of this, so maybe the cylinders just needed to be exercised a little more.