C30 - Bennett trim tabs problem

[pwojnaro]

During our last short cruise I noticed that the boat wasn't responding to trimming. Stopped to test the tabs and while I could hear the pump running in both directions, tabs wouldn't budge. Haven't had the time to investigate more until now and what I just found is that the system lost most of its fluid. Reservoir is nearly empty and I see a pool of red ATF fluid collected in a small cavity underneath a stern thruster (Bennet pump is mounted above it). The system worked just fine immediately before the departure - I opened the engine hatch as a part of my pre-departure checklist with no problems.

Has anyone experienced a problem like this? I'm planning to test the solenoids next (per Bennett's troubleshooting guide). I'm wondering if broken solenoids combined with running the pump could have cause a leak (and where exactly). Thoughts?

 

[TexasEye]

Removed and replaced both of mine. These are simple plastic Hyd Activators and they do crack. Plus all activators (Hyd) can leak internally causing a failure too. But, what you describe is typical of a body failure (crack) which will require replacement. Easy job and somewhat inexpensive. If you replace one, I'd suggest replacing both.

Oh. being curious, I took mine apart and launched the spring and plunger (and residual fluid) across the shop!

 

[MyOhMai]

I had both of mine fail too and the boat was only 1 year old. But of course I replaced them one at a time. Where was TexasEye advice then? They were both obvious failures, lots of hyd fluid around the transom. Now I test both of them (full-throw) at the dock before each sortie. Oh yeah.... make sure those puppies are ALL the way up before backing-down... lots of stress on those plastic actuators if they aren't all the way up.

 

[scross]

It doesn’t seem to me that you have an actuator leak. If you did, you would see ATF in the water, not in the boat under the hydraulic power unit. Have you checked the plastic cover for cracks or a bad seal?
Let us know what you find out!

 

[pwojnaro]

Thanks for comments everyone.

Weather permitting I'll do more testing this weekend. If not, I'll get it done in a few weeks when I haul her out for some upgrades and winter maintenance.

Regarding the actuator leak, I did see a little bit of ATF around the transom, but I assumed that it was the internal leak that drained to the bilge and got pumped out. I can also see droplets of ATF around the fittings, not sure if this is normal, or if this is the actual leak.

I'm attaching a couple of photos, I'll update here when I find out more.

 

[CAPTCRUNCH]

Judging from the photos, I think I'd start by checking the tubing connections on the power unit. The installation instructions quoted below suggest that it is important to not overtighten the nuts, which I guess would deform the ferrules.
"To connect tubing to the pump, insert tubing through the nut with ferrule fitting and push into the pump-face fitting until it bottoms. While continuing to bottom the tubing in the fitting, tighten nut “finger tight,” then one full turn with a ½" wrench … no more."

 

[ixlr8]

It also looks like you have an electrical cable that needs cleaning and re-tightening.

 

[pwojnaro]

After testing the HPU and finding no problems with the motor or the solenoids, I figured it had to be external. Just a did a haul out a few days ago, and here we go.

 

[JonR]

I'm not sure I'm seeing what I'm seeing. Has the right Bennett trim hydraulic assembly actually come apart? If so - wow!

 

[pwojnaro]

Yeah, here is a better photo. I have no idea if it just came apart by itself, or if I hit something (submerged log?) with that tab.

 

[scross]

I’m just surprised you couldn’t see that from the dock! I know they are under the swim platform but, at least on a R25 Classic, they are easy to visually check.

 

[Sharron]

How many seconds are needed to lower the tabs and again to raise them?