Trim Tab Head Scratcher


rclementtx

rclementtx

Member
I'm reaching out to the forum because my communications with Bennett on my trim tab quandary got a "we don't know what caused this problem" response. Here's my note to them of earlier in the week ...

For the record, I did nothing to the tabs today that I don’t normally do … full down to get up on plane, then short 1 second pulses to trim out the boat and adjust for out of balance position.

When I returned to my slip and powered down my engine, I notice that the PORT tabs had retracted to their normal full UP position but the STBD tabs were clearly stuck in a full DOWN position. I believe that the full DOWN happened after I brought the boat back into my slip since I don’t recall any handling problems when cruising.

I powered back up the engines / tab system and tried both STBD and PORT tabs again – PORT moved up / down normally. STBD was “hard stuck” down and attempts to go up or down (with the helm indicator / controller) over several minutes of trying were of no avail. The hydraulic pump sounded “normal” to me and virtually indistinguishable between STBD and PORT. Finally - after holding the indicator / control in the UP position for about 30 seconds - I heard a loud click (thud?) and noticed that the STBD tab was moving again. I cycled it up / down multiple times and it appeared to operate normally. When I powered down the system the hydraulic pump ran for 15+/- seconds and both sets of tabs retracted. So at this point all seems normal. It sounds to me like the hydraulic cylinder “hung up” at its full extended position, but how that happened is not clear to me.

Can you suggest what caused the STBD tab to hang DOWN and then suddenly release itself with a loud click / thud? Should I be taking any actions either to trouble shoot, to repair or to prevent recurrence??

The "engineer in me" leads me to believe that this was an internal mechanical issue within the actuator and not a hydraulic or solenoid valve issue given the significance of the "thud" that I heard / felt when the STBD tab got unstuck. Since my boat is on a lift, the actuators are only immersed when running and there is no corrosion / buildup on the hydraulic rams that should be causing them to hang up (from external means).

Has anyone on the forum experienced a similar issue? If so, can you shed light on the cause and the fix?
 
Mmmmmmmm, are you still under warranty, sounds like you should be.....just a reference point.

As for what caused it....I have no experience like this, other than have you checked the fluid and does it look "normal". It could be an anomaly that never happens again...

But I do agree, I would want to try and figure it out....I will keep thinking and if something comes to mind I will post an update.

I am sure other more mechanically minded folks might jump in of course....
 
have you read the manual on how these work?
There is one motor total, and 2 valves that open/close.

The motor spins each way, resulting in tab up/down, when the corresponding valve is opened. The valves lock them in place.
Thus you can never put one up, and one down at the same time. (motor would be trying to spin both ways at once).

My guess is one of your valves is sticking. I'm no expert, but I just threw a new HPU in mine for $200 something to fix it. You can replace the valves and such, but... who has time right?
 
SabrToothSqrl said:
have you read the manual on how these work?
There is one motor total, and 2 valves that open/close.

My guess is one of your valves is sticking. I'm no expert, but I just threw a new HPU in mine for $200 something to fix it. You can replace the valves and such, but... who has time right?
Click to expand...


Indeed, I've scoured the manual, the web site, their YouTube troubleshooting videos and anything else I can find on the internet. My initial reaction was that it was a valve problem, but when the tab finally came "free", there was a resounding "thunk" which sounded like something was caught mechanically and that it was much more than a valve opening. The fact that the tab moved up/down after coming free tends to reinforce why I"m leaning toward a mechanical problem. Life would be (relatively) easy if this was an HPU or a valve, since I can get to them. I'm not relishing the thought of getting to the hydraulic tubing coming thru the transom if I have to replace an actuator. I'll troubleshoot further once I get more input from the forum.
 
Without a pic and some measurements I'll take a SWAG. If the tab is going at an angle a bit more straight then it should, the tab can get hung. The only way this can happen is if the cylinder was placed on the transom to close to the tab by manufacture, or something is bent, or not correct.

As an example, front buckets on backhoes can get stuck in the full dump position over time IF (big if) the stop plates wear down. If these stoop plates wear, then the bucket gets barely past the cylinders straight up/down position. When this happens, the cylinder when retracting trys to bring the buck up backwards (so to speak)
 
AllDodge said:
If the tab is going at an angle a bit more straight then it should, the tab can get hung. The only way this can happen is if the cylinder was placed on the transom to close to the tab by manufacture, or something is bent, or not correct.
Click to expand...

Thanks AllDodge ... in my case the STBD tab was probably angled down in the 20+/- degree range. I was actually surprised how far down it appeared to be since I'd never seen the tab in a full down mode before. It is hard to see over the end of my swim platform when the boat's in the water. I have no idea whether the cylinder is mislocated on the transom, but you'd think that Formula would get this right after all the boats they built. When I go to the boat this weekend, I'll do some measurements on relative placement of transom mounting on Port vs. Stbd actuators as part of my investigation and report back here if there is any substantial deviation between the two. Incidentally, in terms of wear my boat has 77 hours on it - not much compared to the reported hours I see elsewhere in the forum.
 
We did a Lenco electric swap and never looked back. It was probably the best $225 I ever spent. My issues were not related to stuck cylinders though.
 
I looked long and hard at going electric. for the cost of the HPU, I could go all electric and later add that switch with the indicators, and have auto retract at ignition off, etc...

But they said up to 28' boats... not sure why my 29 wouldn't work, but whatever...
 
SabrToothSqrl said:
I looked long and hard at going electric. for the cost of the HPU, I could go all electric and later add that switch with the indicators, and have auto retract at ignition off, etc...

But they said up to 28' boats... not sure why my 29 wouldn't work, but whatever...
Click to expand...

I didn't see a size limitation on the retrofit kits. We replaced the Bennetts on our 33' and they worked perfectly.
 
So I thought an update on this topic would be in order - after a half dozen emails and three phone calls with Bennett, plus about 3 hours of troubleshooting in the boat. It appears that my hydraulic cylinders are jamming in their fully extended (down) position and that they need a "kick" to raise back up. According to Bennett, this is a very rare issue and I got no satisfaction regarding why / how / how often it happens, if ever. I've learned a whole lot about this system that is worth sharing though, so here's my contribution to the Forum's knowledge base. Point 1 - the tabs rely on the hydraulic pump to be driven down ONLY. They are designed to rise back on their own thanks to an 80 pound spring in the cylinders. The closed solenoid on the hydraulic pump is the single means in the system that keeps the tabs down. Thus when you raise the tabs, the solenoid valve on the pump opens, the pump pretty much "free-wheels" in reverse, and fluid drains back to the reservoir. The fluid is NOT pumped when tabs come up. Point 2 - For tabs that are stuck down (fully extended), the "acid test" is to disconnect the hydraulic lines on the hydraulic pump and to see what happens. In proper operation, the lines should drain hydraulic fluid into the boat as the cylinders retract from spring force ON THEIR OWN. If they don't retract and drain fluid, there's a blockage in the lines or a jam in the cylinder. Point 3 - Since the hinge in the tabs themselves (where they connect to the transom) can get crapped up (mine were really sluggish before lubricating them), the ultimate test of the cylinder is to see if it retracts on its own when unscrewed from the tabs (with the hydraulic lines disconnected at the pump). Mine didn't until I gave it a good "kick", applying 20-30 pounds of force. Then once freed, they returned on their own. What's really strange is that my "one tab stuck" scenario expanded to "both tabs stuck" over less than a month. Such a double failure is a double "head scratcher" to me, but I've duplicated my cylinder sticking several times now. While Bennett will provide replacement cylinders, installation is to my account. Thirty years ago, I might have been nimble enough to reach down to where the hydraulic line and position sensor comes thru the transom on each side. But today, I'm going to have to pay a nimble quasi-midget to do that work for me. I hope this helps others that face this problem. One plus is that Bennett is quick to answer emails, and both accessible and reasonable to deal with on the phone.
 
Just thought of something else

Since its just the lower section of the cylinders, you could replace them in 30 minutes or so. Boat is on the hard, remove 2 screws which fasten the lower cylinder to the tab. Install the plastic clip on the cylinder rod. Unscrew the cylinder off the hinge. Refill new cylinder with ATF and screw back in place. Remove clip and put the 2 screws back in.

Refill the cylinders so you don't have to get to the pump to add fluid to it
 
AllDodge said:
Since its just the lower section of the cylinders, you could replace them in 30 minutes or so. Boat is on the hard, remove 2 screws which fasten the lower cylinder to the tab. Install the plastic clip on the cylinder rod. Unscrew the cylinder off the hinge. Refill new cylinder with ATF and screw back in place. Remove clip and put the 2 screws back in.
Click to expand...

First off AllDodge - you win in terms of trim tab knowledge. I'll pulse Bennett on your idea tomorrow. I think they are mystified on where the hangup is though and thus they offered full cylinder. I'd love to avoid that if possible.
 
rclementtx said:
I'll pulse Bennett on your idea tomorrow. I think they are mystified on where the hangup is though and thus they offered full cylinder.
Click to expand...

Bennett advises that I need to replace the whole actuator. I think the nature of my anomaly is strange enough to them that they don't yet know what caused the problem so they're into a full replacement mode. The good news of this mess is that, since I'm still in the 5 year extended warranty / insurance program provided by Formula, AMTrust has agreed to pick up the labor cost for the replacement effort. Overall, this seems to be headed to the best of all possible resolutions. This 5 year warranty that Formula provides is a "class act".
 
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