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Hooking tach up - MFS40A

F

F909

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I would like to hook up a tach to my Tohatsu 40HP 4 stroke. I know I can buy the $100 tach plus the $45 wiring harness, but is there another way? Ignition wire and signal wire, but I don't know which color wires to look for. Thanks for any help.
 
Outboard tachometers use the alternator as a signal. You can try an el-cheapo induction tach, but most will not work on a 3-cylinder motor, and will cost around $45... your cost will not be that much less, and odds of success are mediocre. I always recommend the OEM instrument. The MSRP on that motor is over $7K. Isn't a good, reliable tach that is specifically designed for that motor worth $100?
 
I have used the induction type tachs in the past with "ok" results. I am trying to go with a smaller tach than the OEM has to offer. I have about a 3.75" area to work with, so I need one of the little 2" models. I Googled quite a bit last night, and see that Faria makes a smaller tach, and correct me if I am wrong, is the same manufacture of the OEM tach. What I can't get a straight answer on the wires to tap into to make the tach work. I have a box near the air intake on the front of the motor, and in that box is a connector with only two wires going to it, blue and white. If these are the wires for possibly an "accessory" type wire that is only hot when the key is in run mode, and the other wire is the tach signal. Anyway you can verify this Paul? If so, I can cut that connector off, replace with with different connectors and run my wires out. Thank you for the help.
 
Is the smaller tach an alternator tach, or is it an ignition signal tach? That will make a difference. The alternator signal and ground are the white and yellow wires on carbureted Tohatsu outboards, and the tach meter must then be set to the correct number of alternator poles. If you have a Remote motor, you would typically connect to the RC box, rather than at the motor itself. Full information is in the Factory service manual, which is available from any dealer. I can't recommend the aftermarket manuals. If you need more information, I would suggest you contact Tohatsu America directly at 214-420-6440.
 
Paul thank you for the wiring tip. How much is the factory service manual and is there an option for a digital download?
 
[h=5]SERVICE MANUAL - TOHATSU - MFS40/50A 4STR[/h]
003-21067-0_lg.jpg

DescriptionCovers MFS40A and MFS50A 4-stroke models
Part #: 003-21067-0
List Price (MSRP): $100.00

Because it is copyrighted, it is not available for free download, but any dealer can get you one. Dealers are sometimes able to discount off MSRP.
You can find a local dealer on the Tohatsu website, by using the "dealer locator" feature.

 
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