Trim tab problem on 2001 3988-gctid821367

[Ahaua]

My port side trim tab will not operate. I've checked fluid level in reservoir and it's ok. When I try to operate the trim tab, I can see some bubbles coming from the trim tab shaft area. Any ideas on repairing will be greatly appreciated. I'm thinking the boat probably needs to be hauled out of the water?

Thanks!

Alex

[Tabman]

Do you know if they are Bennett or Boat Leveler?

Tom

Bennett Marine

[mlewis100]

I have the same issue on our 3587. We have Bennett trim tabs.

I can hear the motor/pump running when the when port and starboard up/down rocker switches are depressed but only the port tab move up and down, the starboard does not move.

I was in the water swimming and cleaning the tabs, rudders, props, Etc. a few weeks ago while at anchor. I got my wife to operate the switches and even pushing on the trim tab a bit when trying operate the starboard tab switch but it would not budge.

I have confirmed the fluid level is up.

I suppose it is most likely the starboard actuator or the starboard portion or the pump. The actuator requires a haul-out to replace out the pump doesn't, which make the pump easier to replace if you have to pick one.

Is one of these two items more likely to fail than the other? The actuators don't have any foul on them; are they otherwise likely to seize? Do the pumps require replacement typically? Does anyone have any experiences they wish to share?

Thanks in advance.

[Tabman]

For both it's likely a switch, wiring or pump issue , not the actuator.

Below is troubleshooting, please try step 3 and 6 and let me know what you find.

Tom

Bennett Marine

Fluid: Automatic Transmission Fluid (ATF) any type. Hydraulic Power Unit is self bleeding, running the Trim Tabs up and down 3-4 times will purge air from the system.

Fuse: 12 volt system use 20 amp in-line fuse on positive. (24v & 32v use proportionately smaller)

Red= Port Valve

Green= Starboard Valve

Blue=Motor Forward (pump pressure)

Yellow= Motor Reverse (pump retract)

Black on HPU=Ground

Orange on Helm=Control Positive

Troubleshooting

1.If one side is not operating reverse hydraulic lines on the front of the Hydraulic Power Unit to determine if the malfunction is in HPU or actuator / hydraulic lines. If after reversing the lines symptom shifts to the other side the malfunction may exist in HPU. If the symptom remains on the same side, malfunction may exist with the actuator / hydraulic lines

2. Is the unit receiving a solid 12 volts? Low voltage will some times cause the solenoids to not open preventing the tabs from moving even though the pump motor is running.

3. Conduct the following test:

Remove the wires from the helm control and touch together as follows:

Operation=Reaction

Orange (+), blue, red= Port trim tab down

Orange (+), blue, green=Starboard trim tab down

Orange (+), blue, red, green= Both trim tabs down

Orange (+), yellow, red= Port trim tab up

Orange (+), yellow, green=Starboard trim tab up

Orange (+), yellow, red, green= Both trim tabs up

If the trim tabs function correctly for each wire grouping then the switch is at fault. Also note that any loose or missing screws on the back of the switch (whether a wire is connected there or not) can cause the pump to malfunction.

This test may also be done right at the pump by substituting a "hot lead" for orange. There is usually a connector to the wire harness within a foot or so of the pump. You want to check this connection for corrosion. You may wish to cut the connector off on the pump side and try the test on bare wires.

4. If you suspect corrosion on the wire connector near the pump, cut it out, test as above and reconnect using butt splices.

5. If you conclude the problem is in the pump, contact me. Bennett Trim Tab pumps carry a five year warranty.

6. Check to see if there is a relay in line on the wiring harness near the hydraulic power unit. If there is it is an Interrupter Relay (IR1000). It prevents the system fuse from blowing if you try to actuate one trim tab up and the other down at the same time. After you test as outlined above, try removing the relay from the wiring harness and retest the unit.(Note: the interrupter relay is no longer used in current Bennett Trim Tab systems and has been replaced with a Switches that "lock out" preventing a blown fuse).

[mlewis100]

Hi Tom, thank you for the great explanation!

Your support example illustrates a great reason to stick Bennett trim tab systems.

I will go through your suggestions and try to narrow down the issue next week.

Thanks again.

Matt

[Ahaua]

Tom,

Thank you for the reply; I'll check on which trim tabs I have when I'm back at the boat, all the documentation is there. The boat if fairly new to me, (purchased it at the end of March). Will get back to you. My buddy, Jim Gandee mentioned that you're the trim tab guru...

Thanks again!,

Alex

[Ahaua]

M Lewis,

Thanks for sharing your situation; it looks like we may have a similar problem. I'll continue to read the thread as it appears that TabMan may have some good advice.

Alex

[Ahaua]

Tom,

Really appreciate your advice! I'll do as instructed and report back with my findings.

Thanks again!

Alex

[Ahaua]

Tom, (Tabman),

I verified that I do have Bennett trim tabs and, after following your troubleshooting instructions, I found that by switching the hydraulic lines at the pump, the port trim tab worked fine and the problem was transferred to the starboard tab. If I'm understanding it correctly, this rules out an actuator and/or hydraulic line problem. The culprit appears to be the Hydraulic pump unit. I did check the wiring connector near the pump and did not see any evidence of corrosion.

Another observation was that, when I returned the hydraulic lines back to their original positions on the pump, the port trim tab will partially go down, (it's sluggish), but will not come back up. I also tried switches on both the down helm and the upper helm; same symptoms so it doesn't appear to be a switch problem.

I'm planning on buying and installing a new Bennett pump; does this seem like the right thing to do?

Once again, thank you very much for your instructions!

Alex

[Ahaua]

Btw, attached is a picture of the Bennett pump.

Alex

[Tabman]

I sorry but your post got in under my radar!

Did you do step 3?

Or did you buy a new pump?

What was the outcome?

Tom

[Ahaua]

Tom,

Thanks for the follow up; I really appreciate your help. After I swapped the hydraulic lines and the symptoms transferred to the other side, It appeared that the problem was possibly the solenoid on the pump for the port side. Instead of investing into a really old pump, I went ahead and ordered a new Bennett pump. When I received it, it had damaged threads on one of the ports so I returned it for an exchange and am still waiting for a new one.

I didn't follow step 3; however, I did find that both the upper helm switches and lower helm switches produced the same results so I figured it's probably not a switch problem.

Once I install the new pump, I'll report back with the results; will keep my fingers crossed.

Your instructions were a tremendous help and it ruled out a bad actuator which probably would've required a haul out.

Thanks again!

Alex

[Ahaua]

Tom,

I installed the new Bennett pump yesterday and trim tabs are working fine; thank you so much for the advice!

Alex

[Tabman]

Outstanding, Glad we could help!

Tom

Bennett Marine