Trim tabs

Bob Giaier · Post by **Bob Giaier** » Thu Dec 20, 2012 9:28 pm

Our 73 Tri cabin is the first boat I've had with trim tabs. That being the case I didn't think anything about having to keep pushing my trim tab buttons every few minutes while on plane to keep the bow down. That is until someone told me otherwise. In other words, once I've pushed the buttons to get the bow down, I have to keep pushing the buttons to keep the bow down. Is there a check valve in the reservoir that I can clean or replace on these?

The unit is the original Leveler. leveler was very helpful when I rebuilt the cylinders last year and I can probably talk them about it, but I thought maybe someone out there has dealt with this problem.

Thx in advance for your help

Big D · Post by **Big D** » Thu Dec 20, 2012 10:57 pm

Chances are the solenoid valve is leaking, there are two of them; one for port, one for starb. To extend, the hydraulic pump turns on, valve opens thus extending tab. The pump does not need to operate for retracting the ram. The spring in the cylinder forces the fluid back into the reservoir once the solenoid is activated/opened. If you need to keep activating the pump to keep the fluid in the cylinder, then it is bleeding back through the solenoid.

http://www.insta-trim.com/solenoid-valv ... -volt.html
http://www.insta-trim.com/owners-manual
http://www.insta-trim.com/parts.html

captainmaniac · Post by **captainmaniac** » Fri Dec 21, 2012 10:05 am

Second thing to check is for is low fluid level / system sucking air and needing bled, or leak in the hydraulic lines...

Big D · Post by **Big D** » Fri Dec 21, 2012 10:47 am

captainmaniac wrote:Second thing to check is for is low fluid level / system sucking air and needing bled, or leak in the hydraulic lines...

I thought about that but if they are extending, then they come back on their own, then air or lack of fluid shouldn't be the issue. Once they are extended, they should remain there, fluid/air or not....right?

Bob, are you sure they are actually retracting, and not simply the way the hull is responding for some reason? Notice any change in RPM, the way the engines sound, etc? The other thing I neglected to mention is that a stuck or shorted switch at the helm will also cause the solenoid to remain open. Even though you aren't touching anything, electrically, it may be activating and retracting the rams.

Tabman · Post by **Tabman** » Fri Dec 21, 2012 5:45 pm

Big D is probably right. If the valve seats on in the solenoid vales are cracked or fouled by some debris they will let the fluid slowly move back into the reservoir.

To test to see if this is happening put both Trim Tabs fully down and leave them there overnight. If the valves are bypassing they will retract on there own. If you cannot see the Trim Tabs you can use a boat hook or something like it to find the trailing edge of them and mark it against the the swim platform or transom top to see if they retract.

You may be able to tale apart the valve and see if the valve seats are fouled, and clean them.

Tom McGow
Bennett Marine

captainmaniac · Post by **captainmaniac** » Fri Dec 21, 2012 6:09 pm

Don't disagree with the valve diagnosis at all... just throwing a couple other things out there that I have seen.

Re low fluid / air in the system - a valve or clamp that can hold or doesn't leak fluid (or doesn't leak very fast) may not be able to hold air very well. Initially pressurized with the air / fluid mixture, the air could seep out (losing trim) until its just fluid, which may hold.

Fluid leak is more likely to affect one tab (than both). A few years back while on vacation I noticed that I kept having to trim one tab down to keep the boat level. After levelling it would run fine for a while, but several minutes later I had to add more tab again. Thought that was weird. That night walking around the marina I saw a huge slick on the water and started ranting about idiots who have no pride of ownership, are too cheap to buy marina gas and end up spilling jerry cans all over the place, or have oil in the bilge that they just pump overboard....

The next day we headed out and I had trim problems again, so had my wife hit the switch while I looked at the tab to see if it was moving okay. The bubbles told me what was really going on, and (unfortunately) who the idiot creating the slick the previous night was.

captainmaniac · Post by **captainmaniac** » Fri Dec 21, 2012 6:16 pm

Tabman wrote:To test to see if this is happening put both Trim Tabs fully down and leave them there overnight.

Good suggestion actually... but I would think that they would only retract on their own overnight if it was an electrical issue that tripped the 'up' circuit. With no pressure or force other than gravity acting on the tabs, shouldn't they stay down?

If they come up on their own over night, it is an electrical glitch. If they stay down, it is more likely a pressure problem (valves or leak related... while the boat is moving through the water the hydraulic system can't hold up to the pressure being exerted on the tabs).

Separately - while sites like this often get trolled by sales guys and marketers trying to push their own stuff, it's good to see a supplier contributing by simply sharing their knowledge and expertise, and not spamming everyone by trying to convince them to switch over!

Tabman · Post by **Tabman** » Fri Dec 21, 2012 6:37 pm

captainmaniac wrote:
Tabman wrote:To test to see if this is happening put both Trim Tabs fully down and leave them there overnight.
Good suggestion actually... but I would think that they would only retract on their own overnight if it was an electrical issue that tripped the 'up' circuit. With no pressure or force other than gravity acting on the tabs, shouldn't they stay down?

If they come up on their own over night, it is an electrical glitch. If they stay down, it is more likely a pressure problem (valves or leak related... while the boat is moving through the water the hydraulic system can't hold up to the pressure being exerted on the tabs).

Separately - while sites like this often get trolled by sales guys and marketers trying to push their own stuff, it's good to see a supplier contributing by simply sharing their knowledge and expertise, and not spamming everyone by trying to convince them to switch over!

Boat Leveler (and Bennett) have large springs that force the piston up. We use these to help retract the Trim Tabs when there is no water pressure pushing against them. Since they are single acting systems that only have one fluid line supplying fluid to the top of the piston we need that spring to help return the piston to the retracted position as the pump evacuates the fluid.

If you put both Tabs down and turn the electrical supply off to the system and they retract on there own, it will confirm that the valves are bypassing.

Tom McGow
Bennett Marine

Tabman · Post by **Tabman** » Fri Dec 21, 2012 6:43 pm

I forgot to add that the valves open when power is applied to them. When there is no current they are in the closed position and should hold the pressure in the actuators (rams) and hold them in position.

Tom
Bennett Marine

Big D · Post by **Big D** » Fri Dec 21, 2012 7:28 pm

Tabman wrote:.... If you cannot see the Trim Tabs you can use a boat hook or something like it to find the trailing edge of them and mark it against the the swim platform or transom top to see if they retract....

Or just look at the reservoir! After extending, most of the fluid will leave the reservoir, you should be able to see the level of the fluid through plastic. When you return, if the fluid level is up again, then the only conclusion can be that fluid has leaked back and the ram/s have retracted.

Tabman · Post by **Tabman** » Fri Dec 21, 2012 7:43 pm

Big D wrote:
Tabman wrote:.... If you cannot see the Trim Tabs you can use a boat hook or something like it to find the trailing edge of them and mark it against the the swim platform or transom top to see if they retract....
Or just look at the reservoir! After extending, most of the fluid will leave the reservoir, you should be able to see the level of the fluid through plastic. When you return, if the fluid level is up again, then the only conclusion can be that fluid has leaked back and the ram/s have retracted.

What he said!

Bob Giaier · Post by **Bob Giaier** » Fri Dec 21, 2012 9:38 pm

Wow, thank you everyone for such a thorough reply. Since our boat's on the hard (we're in Michigan), I can check to see if the tabs retract over time once I extend them. Should be easy to check.

I will check the reservoir level, but as was mentioned they would probably leak unevenly causing the boat to be uneven which it I don't recall that.

Tabman, if to retract the tabs the solenoid opens and the springs do the work to retract the tabs, why do I hear the hydraulic pump running. The hydraulic pump runs when retracting or extending. The tabs do retract and extend properly with the switches.

Can air still be trapped in the cylinders from when I rebuilt them? If so doesn't the air bleed out once the tabs are cycled several times?

Thanks again for the input

Bob Giaier · Post by **Bob Giaier** » Fri Dec 21, 2012 9:40 pm

I'm having trouble trying to eliminate a duplicate post reply. Don't know why it doubled my reply, oh well

Big D · Post by **Big D** » Fri Dec 21, 2012 9:49 pm

Bob Giaier wrote:....if to retract the tabs the solenoid opens and the springs do the work to retract the tabs, why do I hear the hydraulic pump running. The hydraulic pump runs when retracting or extending....Can air still be trapped in the cylinders from when I rebuilt them? If so doesn't the air bleed out once the tabs are cycled several times?...

Yes the pump does operate in both directions. It is a powered retraction but the force of the spring on it's own can cause the fluid to pass through a leaking solenoid. Air might still be trapped but air on it's own shouldn't cause the bleed-back. Yes, operating the tabs several times is the way to bleed air from the system. Once bled, it will operate smoother, faster, and you will note a different sound at the pump.

Bob Giaier · Post by **Bob Giaier** » Fri Dec 21, 2012 9:54 pm

Then it shouldn't be air. The rebuild was last spring and they've cycled many many times and do operate smooth and fast.