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How to install your own trim tab (along with a few easily avoidable goofs)


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Step One: Acquire Your Parts

 

Midnightv10 and I decided to split a lenco trim tab kit to maximize cost savings.  Several other posters on this forum have suggested that the lenco 12x18 edge mount kit would work, so that's what we went with.  Remember the factory tab is made especially for MB, and is 12x16, and has a different hinge to accomodate the drain plug and the factory exhaust.  There will be some modification involved.

 

The best price I found was at imarine, but your mileage may vary: https://www.imarineusa.com/lenco12x18edgemountkitwoswitchtt12x18ens.aspx

 

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A note about imarine... while they do have a lot of their catalog in stock, they also list WAY more than their actual stock on their website.  Once you order they arrange for drop shipping from a manufacturer or distributor.  If you call ahead they are very up front about this.  Also know that if you go with imarine it's going to take a few weeks.  Be patient.

 

For switches, we went with the lenco branded carling rockers, and agreed to split the switches.  

https://www.imarineusa.com/lencocarlingdoublerockerswitchkit.aspx

 

 

As Greeko has pointed out in recent days, you can certainly save a few bucks from the $30 a switch if you do it yourself.  There is nothing special about these (on)-off-(on) momentary rocker switches, and there are lots of places to find them online.  The nice thing about the lenco switches is that they are pre-wired and come with very nice deutsch connectors that make wiring the tab a breeze because it's plug and play.  The other thing to consider is the switch cover, which is a contura v, and matches the switches MB uses on the dash.

 

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Midnight and I also had a brilliant idea to use a bennett auto retract box and an RPM window switch to make the tab retract at speed.  The bennett box goes between the switch and the actuator and sends a signal when a constant power trigger is interrupted (like your ignition, if you wire it up that way).  I spent a little extra and bought a set of deutsch connectors to get the bennett box wired to the lenco switch without hacking it up.  Summit Racing sells the Deutsch DT connectors you need to add a plug and play segment between the switch and the actuator here: http://www.summitracing.com/parts/msd-8183

 

I used summit because they are local, so if you are looking for another source for the connectors, just make sure you get DT connectors.  This was my first time using Deutsch connectors and I was impressed.  They are very nice.

 

As noted, much to my chagrin, I found that the Bennett box will not work with Lenco actuators.  Bummed!  I'm not giving up though and I will post more on this issue in the next week or so, with proof of concept for plan B.

 

So that's really all you need, a trim tab and a switch.  Doing this on a budget, especially if you have someone nearby with whom you can split shipping, you could do it with "factory" lenco parts for as little as approximately $275 (assuming you have marine adhesive on hand and you don't buy the extra deutsch connectors).

 

 

STEP TWO: The Install

 

These tabs are heavier than I expected and they are super awkward to hold up to the transom to line up for drilling holes.  So I taped the back of the hinge up with 3M VHB tape from my local walmart, and stuck it to the transom to mark holes.  

 

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As mentioned above, the lenco hinge needs to be modified to fit the MB transom.  My tab needed two cuts.  One to clear the drain plug and one to clear the exhaust tip. I was a little gun shy cutting the tab so I had a local trusted machine shop cut the notch for the plug.  That cost about $46.  Then I got home and realized that I still needed to clear the exhaust tip.  Ugh.  Well I wasn't going to pay another $46 to make that cut, so I got out the dremmel.  With a cutting wheel attached I had the hinge notched for the exhaust tip in about 5 minutes.  Should have done the other one myself too, in retrospect.  Oh well.

 

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This is a larger-than-factory tab, and I was concerned about the 18" wide tab fitting a measured 17.5" transom flat spot.  There is definitely a little overhang, but I convinced myself not enough to worry about.  You be the judge.

 

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I wanted to get all of the electrical done first, so after I marked the tab for drilling, I pulled the wire and installed my trim tab switch.  I'd seen this location used in the past on here, and I'm glad someone else did it first because I probably never would've thought of it.

 

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I'm using the two gauge switch plate because I'm putting a second switch in so I can toggle between auto retract (assuming I get it working) and full manual.

 

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Absolutely spend the time to tape off the boat before you cut the fiberglass.  I did not do that when I installed my heater hot tubes and my boat is still filthy.  I don't think I'm ever going to get rid of all of the fiberglass dust.

 

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A nice harry arm pic to show the results of some drilling and dremmeling:

 

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I used the dremmel cutting wheel again to cut the fiberglass (same one I used to cut the trim tab hinge), and then cleaned up the hole with one of the little sanding drums.  Got the switches installed.  The "Shower" actuator cover is just a placeholder for the on-off auto launch feature i'm working on.  I got a stereo actuator cover for where my shower switch, so this was left over.  The switch itself is a carling v4d1 from Mouser Electronics.  It's an on-on toggle switch, basically the same style as the switch for the ballast tank gauges.

 

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After the switch was in I hooked up the lenco actuator manually to make sure it worked.  No problems.  Time to mount the tab.  oh the adrenaline rush of drilling 16 holes in your boat below the waterline in a single sitting! The lenco kit ships with all of the mounting hardware you need to get the tab to the boat.

 

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Doh! It's not a DIY project without at least one thing to look at and drive you crazy.  I had the major brain fart moment of the day here.  Once the tab was on the last step is mounting the actuator.  And for whatever reason, I put the the top bracket upside down (as pictured).  Well, when you do it that  way, the step in the hull interferes and you can't get the actuator high enough (the tab will be "flat" whereas lenco calls for the tab to be 3/8" higher at the trailing end than the tab at the hinge.  So I mounted "high" to get the clearance, figuring I'd shim the bottom mounting point.  Duh, I'm pretty sure I could've flipped that mounting bracket over like MB does and it would've fit just fine.  That's why I don't do this for a living I 'spose.  To be clear, do not mount the top bracket like this:

 

 

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Midnight also called me out for my aesthetic goof of mounting the Lenco sticker "in" instead of out so you can see it.  Turned it around and made a couple of hdpe shims for the bottom mounting foot of the bracket.  This gets me to 1/2" of rise overall.  As a DIY guy being within 1/8" of spec puts me squarely within the "meh, close enough" range.  Here's the turned around actuator fully extended with the shimmed base plate to make sure it works:

 

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Part B, the auto retract feature, to follow later this week, I hope.

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Great write up SD..

 

Taping the tab up to mark the holes is an excellent idea.. I would not have thought of that.

 

So I have been thinking about your actuator mounting "lesson learned". The spacer definitely looks like it works fine

however by having the upper mounting bracket up so high, geometrically you are loosing about an inch and a quarter of deployment depth.

Sky Ski sent me some pictures of his "Factory" tab a while back with dimensions at 1/4, 1/2, 3/4, and full deployed. The tip of the factory tab has 4" of depth below the plane of the hull when full deployed. Based on the Geometry of where yours is mounted I am going to guess you will only have about 2-3/4" maybe 3" of depth. Now I have no idea if this is even an issue but if it is here is one solution I see.

 

If you flipped the lower mounting bracket around 180 degrees the connection point of those two legs of the triangle would be closer in towards the transom and that would give you additional range of motion...

 

Not a flogging, but an observation from someone who has efd up his share of DIY's

Good work brother B)

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I think it all looks great with great info on what you did and might do slightly different next time. You just saved around $800 for the next guy wanting a tab at a reasonable price. Good job. I see your overhangs, but I doubt they will affect the wave. Post some pictures of the wave/wake when you get a chance.

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Great write up SD..

 

Taping the tab up to mark the holes is an excellent idea.. I would not have thought of that.

 

So I have been thinking about your actuator mounting "lesson learned". The spacer definitely looks like it works fine

however by having the upper mounting bracket up so high, geometrically you are loosing about an inch and a quarter of deployment depth.

Sky Ski sent me some pictures of his "Factory" tab a while back with dimensions at 1/4, 1/2, 3/4, and full deployed. The tip of the factory tab has 4" of depth below the plane of the hull when full deployed. Based on the Geometry of where yours is mounted I am going to guess you will only have about 2-3/4" maybe 3" of depth. Now I have no idea if this is even an issue but if it is here is one solution I see.

 

If you flipped the lower mounting bracket around 180 degrees the connection point of those two legs of the triangle would be closer in towards the transom and that would give you additional range of motion...

 

Not a flogging, but an observation from someone who has efd up his share of DIY's

Good work brother B)

 

Zactly. 3" of throw past "neutral". Going to try it like this for now and see how it does.

 

Love the idea of flipping the bottom bracket! Would never have thought of that myself. I can always marine-tex over my holes in the winter and remount too.

 

I never felt the need for the tab from a holeshot perspective before, so I'm sorta hoping it works as-is for crushing the rooster tail for surfing.

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Yeah, I am with you on the holeshot thing.. my 409 with a 2079 prop at nearly sea level should ensure great holeshot (and great friendships made at the gas pump) so it is for me more of a prop wash thing as well.

 

BUT.... it would always wonder what that extra inch would do.. <_<

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metalfabguy just made reference to an x30 install thread, which I found here: http://www.mastercraft.com/teamtalk/showthread.php?t=39881

 

The one really interesting thing on that thread that I probably would have tried on my install had I seen it is this, a shim to build up the area around the drain plug so you actually mount the tab over the drain plug flange.

 

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I wonder if you could use something like HDPE there in lieu of stainless?  Yeah I know, plastic... but the mounting brackets for the actuator are plastic and they are going to see a lot more force than a sandwiched shim.

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Yeah, I am with you on the holeshot thing.. my 409 with a 2079 prop at nearly sea level should ensure great holeshot (and great friendships made at the gas pump) so it is for me more of a prop wash thing as well.

 

BUT.... it would always wonder what that extra inch would do.. <_<

I have been thinking of getting the 2079 prop for my boat since we surf quite a bit. How do you like it? As for the 409, I don't have that, only the 350.

 

Thanks,

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The more I think about it the more I think the idea of turning the bracket around is genius.  I'd have two empty holes in the bracket then, but seeing as we hit an alkaline lake fairly regularly,  I could certainly put one of the Lenco anodes on one.

 

smallanode_183cd0b83d7ac50c9e32caa281754

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I have been thinking of getting the 2079 prop for my boat since we surf quite a bit. How do you like it? As for the 409, I don't have that, only the 350.

 

Thanks,

Don't know.. I have not put it on yet but several on here have used it and swear by it plus it is the recommended prop for my boat with heavy surf weight.. should be trying it out within a week or so

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Any idea where to source one like on that MC tab?  That's not a lenco part.

not sure - do you remember who posted on TeamTalk?  I am member on there as well and can send them a pm asking.  It looks like Lenco but not sure if that bracket is custom or not....

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The more I think about it the more I think the idea of turning the bracket around is genius.  I'd have two empty holes in the bracket then, but seeing as we hit an alkaline lake fairly regularly,  I could certainly put one of the Lenco anodes on one.

 

smallanode_183cd0b83d7ac50c9e32caa281754

that is a good idea....

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I can feel you man, site work on Mac kills your schedule for weeks at a time...I remember doing it..money was fantastic...but boy did it wear me down!

 

Good luck with all of it

Got that right.. I'm on a 15/6 rotation so not quite that bad... 21/9 is brutal especially in the summer with the limited boating season we have in the PNW... But like you say, the money is awesome...

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