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Installing a Tachometer (revisited)...

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I am starting a new thread on this because I got it figured out... pretty much on my own, if I may add. As a recap, I was trying to put a tach in my boat, a 2007 Lund 1425 Classic SS with a 40 HP Merc 4-stroke EFI. The folks who made the boat (Lund) were of absolutely no help. The folks who made the engine (Mercury) were of little help.

I knew there were some unused wires under the throttle. I checked the wiring codes from Mercurys HSOforum, only to find out that I did not have the correct ones in my harness. I knew I needed Purple (ignition positive), Black (ground), Gray (signal), and Blue (guage illumination). So, after checking, I found this multi-wire pigtail under the throttle in rod-storage:


The big black plastic thing is the key here, not the individual wires. Looking at all the different colored wires in the bundle, I noticed it had all I was looking for. Someone on here mentioned that this pigtail was for hooking up SmartCraft guages... Mercurys own brand of very nice digital guages. This pigtail is supposed to make hooking up guages a snap- literally. I took off the bottom snap-cover and saw that it should be a simple install... buying the guage and hooking it up to this purple connector:


Here is where it got interesting. Mercury confimed what this pigtail was for- hooking up THEIR guages. This was the way all Mercury wiring has been set up since 2006, so it is a relatively new concept for them. So, what would I need to make this work? I was told I would need just two things: a wire-harness that plugs into this recepticle and then a SmartCraft Tachometer. He then quoted me a price of $190 for the wire harness plus $375 for the guage! Totally unacceptable! I've wired tachs before in cars and there was no-way this was going to cost this much. I was missing something here. So, I followed the wire harness to the engine and sure enough, all the correct wires were there and were connected. So, I decided to try something radical... something I'm sure Mercury wouldn't suggest. I got a used working analog tachometer and I tapped into the wires into the pigtail receptacle. I did this by soldering some thin nickel homemade "blades" to some wires and simply plugged them in to the correct slots, correlating to the correct colored wires:


Then, I hooked the wires up to the correct posts on the aftermarket tachometer. I chose to omit the blue (guage illumination) wire, because I saw no real need for it:


Before making the installation permanent, I took the boat out to the lake for a test-drive. It worked, but the settings were all messed up (unless the engine ides at 7000 RPM). All the settings that everyone told me, including Mercury customer service and the Mercury HSOforum were incorrect. The only setting that would read something reasonable was the "6P" setting. Turning the adjuster to this would show me an engine idle of around 800 RPM and WOT at around 5500 RPM...


After everything seemed to work, I made the wiring more sturdy by the receptacle by using some shrink-wrap over the wires (as shown)and tying the bundle with nylon zip-ties (not shown):


Next came the installation. There is a blank coverplate, in a "half-moon" shape, on the console behind the steering wheel. This is presumably where the guage should be installed:


Removing the plate, there are two dimples on the backside... perfect for centering the holes for standard 3 1/4" guages:


Cutting was simple using a Dremel Tool and cleaning up with a file. I put the cover back on to test for clearance:


Then, checked the guage for proper clearance. The guage mounts to the plate with a mounting bar, then I simply re-installed the plate:


All done... and it only cost me about $25... compared to the Mercury quote of $565.

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Yeah... I'm glad I did it. I'm also glad I didn't listen to the customer service reps at both Lund and Mercury. They mostly provided erroneous information, not to mention I saved enough money to buy another sonar, if I wanted to... wink

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Way to stay after it. You knew what you wanted and you went until you had it. It just drives me crazy that companies can set things up so people have to buy thier products then jack the prices up. Glad it worked out for you.

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Thanks guys. I doubt it is truly the proper way to do things, but it works. On top of it all, this only applies to Mercury equipped boats with consoles made since 2006. Now that it has been "figured out", Mercury will have to come out with something different just to re-establish a state of confusion...

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My only concern would be something shorting out / wires coming loose... but it sounds like you guarded against that as best as possible. It's pretty lousy the mercury came out with that connector... you used to just get the wiring harness and you'd be set...


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