Trim Tabs on MS400

[Newtrawlerowner]

I have a 2003 MS 400 with dual trim tabs made by Trim Master. Trim Master is no longer in business.
They seem to go down and up (Spring loaded return). The hydraulic power unit (HCU) has been replaced with a pump made by Bennet Marine. My research shows this is a common upgrade when the original HCU fails.

The controls have no indicator of bow up or bow down. When I move the levers up the tabs move down. They are also reversed. Left lever controls right tab and vice versa.
Inspection of the wiring at the HCU shows the harness has been cut and wired to a 6 terminal plug at the new unit. They may have gotten the wiring reversed. I found a wiring explanation on another website and can rewire myself.

Here are my questions.
When you move the lever up, which way does the tab move?
When you retract the tab under way, how quickly does the tab retract? Or how fast do you notice the bow go down?
Out of the water 1 tab retracts rather quickly, the other not so. The retract works by opening a solenoid on the HCU allowing the oil to return to the reservoir. Out of the water the internal spring helps the tab retract.

And does the left lever control the left tab and right lever the right tab?


Thanks in advance for your help.

 

[Bacchus]

Mine is a later model MS and all Bennett but I think the convention is consistent on most installations.
My switches are on the sloped, nearly horizontal helm panel.
L SW controls L tab
R SW controls R tab
Pressing Fwd end of SW extends tabs and pushes bow down.
Pressing Aft end of DW retracts tab and bow comes up

If yours operates opposite can you simply rotate the SW 180* and correct both issues w/o needing to do any rewiring?

 

[rslifkin]

For which way the switch is wired, it's really about preference. Some people (myself included) prefer the simple solution of "port switch, port tab". Others prefer to cross wire so it's "port switch, port bow", which really means "port switch, starboard tab". Remember that the tabs have a diagonal effect on the boat, so putting the port tab down pushes the starboard bow down.

 

[porman]

To the OP. The Trim Master tabs on our boat operate the same as yours. Pushing the left lever forward makes the right tab go down, making the left side of the bow go down. The opposite happens when pushing the right lever forward.

 

[Blue Tortuga]

Bennett trim tabs

I changed out the tabs in my 2004 MS 400 to the 48” Bennett’s. There is kit to use the existing wiring and controls.
I timed the full operation from total up to total down and it’s 19 seconds.
Also it seems to be a waste of money as they are only useful at WOT to bring th bow down and we never run that fast.

 

[Keysdisease]

The way almost all Trim Tab (and interceptor) manufacturers wire their tabs is the way you describe so the control is intuitive, see below.

Changing the wiring to your preference is easy, it does help to understand how the system works to do it right the first time.

There are 4 wires:

Red Port solenoid
Green Stbd solenoid
Blue Motor fwrd - Tab down
Yellow Motor reverse - Tab up

In order to create an action 2 wires must energize; For example Port Tab down, energize Red and Blue, this runs motor forward and opens the port solenoid.

I don't doubt Blue Tortugas 19 seconds, sounds about right for both tabs at same time. The pump has to push oil into 4 actuators. To move 1 Tab full travel should be half.

 

[Blue Tortuga]

I should have elaborated more, we timed this out of the water after the new installation counting one, one thousand etc. 19 seconds all the way up to down.
Also you want to leave these tabs all the way up when not using to save growth on the rams.

 

[Keysdisease]

For Bennett Actuators growth is not an issue.

They can be painted, they are glass reinforced nylon and accept bottom paint readily. There is no seal in the bottom of the cylinder to be damaged by growth, the seal is on the piston, the bottom of the actuator is where the return spring in housed.

Also you want to leave these tabs all the way up when not using to save growth on the rams.

 

[Newtrawlerowner]

The way almost all Trim Tab (and interceptor) manufacturers wire their tabs is the way you describe so the control is intuitive, see below.

Changing the wiring to your preference is easy, it does help to understand how the system works to do it right the first time.

There are 4 wires:

Red Port solenoid
Green Stbd solenoid
Blue Motor fwrd - Tab down
Yellow Motor reverse - Tab up

In order to create an action 2 wires must energize; For example Port Tab down, energize Red and Blue, this runs motor forward and opens the port solenoid.

I don't doubt Blue Tortugas 19 seconds, sounds about right for both tabs at same time. The pump has to push oil into 4 actuators. To move 1 Tab full travel should be half.

This is a great explanation. Thanks!
I will probably rewire so that left lever down (or back, one switch is on a vertical plane, one on a horizontal) move left tab down.
It appears the shafts on the cylinders are a plastic/nylon as well.

 

[rslifkin]

Typically it's switch forward for tab down, back for tab up. As in, pitch boat forward or aft.

 

[Dougcole]

Our 2005 400 has Bennetts. The stb switch controls the stb side of the boat (which is the port tab). I have set all of my flats boats up that way, so it is what I am used to and I like it that way. My brother sets his boats up the other way, drives me nuts, but to each his own, LOL.


That said, on the Mainship I hardly ever operate one tab independently from the other. It's pretty much both tabs all the way down or all the way up all of the time.


On our boat with twins, which we run at 2800 rpm about 25% of the time (14 to 16 knots), the tabs make a HUGE difference when running at fast cruise. In calmer conditions I've seen boat speed increase by as much as two knots when I put them all the way down with the same throttle settings. I wish they were even bigger honestly, and I am going to add the drop fins at my next haul out.


At hull speed they don't do much though, I agree with that 100%.

 

[Keysdisease]

Those Bennett Trim Tabs should be 48 x 12 with a 1" upfin on both sides and I believe a 1" upfin on the trailing edge. The dual actuators screw through the plane itself instead of a riveted angle which is standard, all 12 gauge.

That's as bulletproof a tab as is practical for a boat like a 400. Mainship/Luhrs shied away from rivets on tabs and Bennett had to work around that issue. The Trim Masters were only used for a year or 2 around the turn of the century in response to electrolysis issues with Bennett Tabs that was due to lack of zinc maintenance.

Should you ever need to replace a tab, a standard Bennett 48 x 12 will be a drop in replacement and the actuators should land in the exact correct place on the tab with the screw holes lining up.

Do not ask me how I know

Our 2005 400 has Bennetts. .

 

[Dougcole]

Those Bennett Trim Tabs should be 48 x 12 with a 1" upfin on both sides and I believe a 1" upfin on the trailing edge. The dual actuators screw through the plane itself instead of a riveted angle which is standard, all 12 gauge.

That's as bulletproof a tab as is practical for a boat like a 400. Mainship/Luhrs shied away from rivets on tabs and Bennett had to work around that issue. The Trim Masters were only used for a year or 2 around the turn of the century in response to electrolysis issues with Bennett Tabs that was due to lack of zinc maintenance.

Should you ever need to replace a tab, a standard Bennett 48 x 12 will be a drop in replacement and the actuators should land in the exact correct place on the tab with the screw holes lining up.

Do not ask me how I know

Hey Keysdisease. I know you were involved with the install/manufacture of those tabs for Mainship, I think I met you at a boat show (either Lauderdale or Miami) where I was a vendor a number of years back and we discussed it. Too small of a world to hide in, sorry.


I like my tabs, but I'd like them to flatten the boat even more if possible. Do you think the addition of drop fins would make a difference?

 

[Keysdisease]

Hi Doug,

No worries. Drop fins should help, they work better on smaller tabs but should provide some additional performance on larger tabs. I don't think you have much more transom to add any additional tab, so your options are limited. Don't even think about increasing the chord, on boats that operate in your speed range it would just add drag.

If you do have space, a larger tab would be the best way to go. It would be just a Tab replacement, you could leave your actuators and plumbing in place.

Try the drop fin, easy and inexpensive. They may very well provide that "little bit more" you're looking for. Ask for Thomas @ Bennett and tell him Steve sent you.

Worked my last Show as a regular employee at FLIBS, retiring end of this month but may still end up working shows, when they have them again, as a sub.

Hey Keysdisease. I know you were involved with the install/manufacture of those tabs for Mainship, I think I met you at a boat show (either Lauderdale or Miami) where I was a vendor a number of years back and we discussed it. Too small of a world to hide in, sorry.


I like my tabs, but I'd like them to flatten the boat even more if possible. Do you think the addition of drop fins would make a difference?

 

[rgano]

I like my tabs, but I'd like them to flatten the boat even more if possible. Do you think the addition of drop fins would make a difference?

I added them for a big difference.

 

[rgano]

My Bennet tab rocker switches are mounted side by side both oriented fore and aft.

The forward sides of the switches are labeled "Bow Down" while the aft ends are "Bow UP," orienting the operator's mind to the concept that the bow's attitude is the thing being controlled. Press the port rocker switch's bow down button long enough results in a port list while pressing the same switch's aft (Bow UP) portion long enough will result in a stbd list. Pressing the stbd bow down and the port bow up and result in a more extreme list - all quite intuitive, to me at least.

Thus if the boat is up on plane and with port list, it is intuitive to press the forward part of the port switch to level the boat. The fact that doing this forces the starboard tab down is irrelevant to me. It just works intuitively, and that's important underway and 20 MPH with lots of other things going on. If I need the bow up in rough seas, it is intuitive to press the aft ends of both switches to raise both tabs which causes the bow to rise.

If when raising the bow the boat ends up with, say, a port list when you let up on the two bow-up buttons, it is intuitive to press the forward part of the starboard rocker switch to get the starboard bow down (actually making the port tab go down), BUT pressing the aft portion of the port side switch (actually raising the starboard tab) would have the same effect and would still conform to the "intuitive" convention in that you are intuitively raising the port bow which has the effect of depressing the starboard bow.

Until I am up "on top" at 2800 RPM on the 315 HP Yanmar, there is not effect from the tabs, and they are fully raised (both switch's bow-up sides pressed until the up limit is reached) until then. They are also raised fully when coming to the end of the run when the boat is slowed for maneuvering.

 

[rslifkin]

Until I am up "on top" at 2800 RPM on the 315 HP Yanmar, there is not effect from the tabs, and they are fully raised (both switch's bow-up sides pressed until the up limit is reached) until then. They are also raised fully when coming to the end of the run when the boat is slowed for maneuvering.

Interesting that you keep the tabs up until after you power up. If I'm intending to get up on plane, I drop the tabs to approximately normal cruise position (guesstimated by button push time, as I don't have have trim indicators). Then throttle up once the tabs are set. Boat climbs onto plane much faster and with less initial bow up attitude that way. Then once it settles onto plane, tweak the tabs as needed. When slowing down, I usually start retracting the tabs as I'm throttling back.

 

[Dougcole]

Yeah, trim the bow all the way down before i power up. I keep them all the way down ithe entire time I’m running at higher speeds.

But I bet y’all’s pilots react a lot more to the tabs than my boat does. The tabs on my flats boat will darn near pitch you out of the boat. I wouldn’t own a skiff without them.

 

[porman]

Many years ago on Lake Washington a salesman was showing a 20 something foot speedboat to a prospective buyer. When he got to the end of the 7 knot zone he floored it and the boat flipped over. One trim tab was down and the other one was up. The boat sank to the bottom. The occupants were OK.

 

[rgano]

Interesting that you keep the tabs up until after you power up. If I'm intending to get up on plane, I drop the tabs to approximately normal cruise position (guesstimated by button push time, as I don't have have trim indicators). Then throttle up once the tabs are set. Boat climbs onto plane much faster and with less initial bow up attitude that way. Then once it settles onto plane, tweak the tabs as needed. When slowing down, I usually start retracting the tabs as I'm throttling back.

I prefer not to load the engine with the added drag. Also with the boat's bow down as fully as it will go once up, I can just touch the tabs in short pushes to get the max speed, discovered by watching it bleed off by a tenth or two MPH before touching them back up to regain the lost speed from over tabbing.

Before adding the drop fins, I could not use enough tab to lose any speed because the bow would not go down that far.

 

[rslifkin]

I prefer not to load the engine with the added drag. Also with the boat's bow down as fully as it will go once up, I can just touch the tabs in short pushes to get the max speed, discovered by watching it bleed off by a tenth or two MPH before touching them back up to regain the lost speed from over tabbing.

Before adding the drop fins, I could not use enough tab to lose any speed because the bow would not go down that far.

Interesting that you notice more engine drag with the tabs dropped before throttling up. I notice the opposite, as the boat spends less time bow up and accelerating. With no tab, my boat won't actually climb quite all the way onto plane at normal cruise throttle, it takes a good bit more.

 

[rgano]

Interesting that you notice more engine drag with the tabs dropped before throttling up. I notice the opposite, as the boat spends less time bow up and accelerating. With no tab, my boat won't actually climb quite all the way onto plane at normal cruise throttle, it takes a good bit more.

Our boats are very different.

 

[rslifkin]

Our boats are very different.

Definitely. It's just surprising to me that the tabs add load getting on plane for you, but it sounds like you cruise with a good bit of tab down. Typically I'd only expect tabs to make planing harder on a boat that typically planes with the tabs mostly retracted.

 

[Dougcole]

I prefer not to load the engine with the added drag. Also with the boat's bow down as fully as it will go once up, I can just touch the tabs in short pushes to get the max speed, discovered by watching it bleed off by a tenth or two MPH before touching them back up to regain the lost speed from over tabbing.

Before adding the drop fins, I could not use enough tab to lose any speed because the bow would not go down that far.

Now you’re really making me kick myself for not installing drop fins at my last haul out.

Also, for the record, part of the reason my boat doesn’t run as dlat as I’d like it to is because we carry a big dinghy on the swim platform.

 

[rgano]

Definitely. It's just surprising to me that the tabs add load getting on plane for you, but it sounds like you cruise with a good bit of tab down. Typically I'd only expect tabs to make planing harder on a boat that typically planes with the tabs mostly retracted.

When I bought this boat sans drop fins, I had to stand at the helm to see anything over the bow at fast cruise - it was dangerous IMHO. I added a 120 feet of chain to the existing 80 feet rode and added the drop fins to make it safe to run fast while seeing well over the bow while seated. And yes, kick yourself for not adding them.

 

[LarryM]

I added drop fins this year and the difference is remarkable. My system is a Bennett ATP (AutoTrim Pro) which has two presets for running angle. The system dynamically adjusts the tabs to maintain that attitude as speed and conditions change. Since I already had stored presets in the system before drop fins, it was pretty easy to see how much difference they actually made.

Essentially, I would say it now requires 20%-30% less tab deflection at either preset to achieve same running angles. That translates to less drag and higher boat speed and/or fuel efficiency.

Before the drop fins, due to the deadrise angle, at cruising speeds and above there was a distinct angled 'rooster tail' spilling from the outboard edge of the tabs. That is now completely gone because the water is being contained by the drop fins and is exiting almost directly aft.

The procedure I use for getting on plane (a hole shot) is interesting. I press the All Dn button and while the tabs are extending, I press one of the presets and advance the throttles. The boat fairly jumps on plane getting over the hump with no black smoke at all. As the bow rises, the tabs begin to compensate lowering it and maintaining the selected preset running angle.

Of course, this is on a full-planing sportfishing boat so the results are likely more noticeable than they might be on a semi-planing or semi-displacement design.

The drop fins are one of the best improvements I have made to the boat so far. Very pleased!

 

[Keysdisease]

As mentioned, Tabs can in almost all situations help a boat onto plane and stay there at speeds slower than they might be able to maintain without tabs. A flats boat would never even think of trying to jump onto plane without tabs down from a shallow flat in a "hole' where getting up fast is important.

The drop fins work better on smaller tabs because they essentially act as a +% of tab area, smaller tab, bigger %, larger tab, smaller %. Does not mean drop fins won't improve tab performance, just less as tabs get bigger.

Happy to hear Larry and Rich both provide positive results from real world, tabs often get a bad rap from some die hard traditionalists