A Testing Tach for Small Outboards

Using a test tach for setting idle speed and verifing wot rpm range is within spec is essential for any boat/motor. On small boats discussed on tinboats, many do not seem to use tachs. While some generic tachs can work with multiple motors, some like older Nissans/Tohatsus, can be finicky, and only like the expensive oem tachs. Then you have to mount and run a power lead.

I picked up a one wire digital tach/hour meter last winter, when I was working on a new to me vintage snowmobile. It works by picking up the pulse in the high tension lead. You just wrap the wire around, and a little electrical tape to hold. Plans included though, using on my small outboards, not just the snowmobile.

Earlier, I ran this tach on my 25hp 2 stroke Merc, and over the weekend on my Nissan 40C. While the Merc fires on every stroke, the Nissan fires at the top and bottom of each stroke. The tach was configurable and handled both. Also has 4 stroke setting for one pulse for 2 revolutions.

It also has a fast/slow update mode. Slow helps for idle speed adjustments where the digital number can jump around. It also has a noise hi/lo feature, which I haven't need to use.

The tach can be found in the link below. I purchased mine, new, off ebay for around $32 w/shipping. So far it has been a great multi-engine tach, and thought it would be of interest to other tinboaters.

https://trailtech.net/tto_tach-hour.html

Nice little tool for all kinds of motors. I'm going to pick one up.

Is this tach waterproof? I have been wanting to add a tach and this looks like the ticket.

Slypike said:

Is this tach waterproof? I have been wanting to add a tach and this looks like the ticket.

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I don't know, but would assume not. Probably just water resistant, ie rain. not submersion. I don't leave it in the boat. Just for testing.

https://trailtech.net/tto.html
Not sure if it's the same one but this one says waterproof.
I use a tiny tach,never comes out the boat...I'd say this is the same.

Zum said:

https://trailtech.net/tto.html
Not sure if it's the same one but this one says waterproof.
I use a tiny tach,never comes out the boat...I'd say this is the same.

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That is the one, just didn't go look in the specs.
Works Connection also has the same tach.

When I started looking, I couldn't find a tiny tach that could do all three, especially the two pulses per revolution. There are some lower cost tach/hour meters, but were notas configurable, either.

I'm not downing tiny tach but I wish I had one like yours.
The tiny tach I have isn't configurable and I'm still not 100%it's working right.
Yours is and atleast i could try it on different settings.

I have been needing a tach for my 2006 mercury 50 hp. Its a two stroke. I don't know anything about tachometers or motors, so I am not sure when my motor hits on each cylinder. Do you think this tach would work for me? I dont want to buy a nice tach that I must mount, I really just want to check my RPMs once. If it will work for my motor, will the OP please explain how I install it... I don't know what wire to wrap it around. Thanks

gajet31 said:

I have been needing a tach for my 2006 mercury 50 hp. Its a two stroke. I don't know anything about tachometers or motors, so I am not sure when my motor hits on each cylinder. Do you think this tach would work for me? I dont want to buy a nice tach that I must mount, I really just want to check my RPMs once. If it will work for my motor, will the OP please explain how I install it... I don't know what wire to wrap it around. Thanks

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Works Connection has a set-up install video on this page: https://worksconnection.com/details.php?id=722 It is for a bike, but should give you enough info/pictures for a outboard. It doesn't get much simpler. I don't hard mount the display. The wire is long enough for tillers, but a console mount will probably require glancing behind you. It also saves peak rpm, which should be correct unless you cavitated during that test run.

For a two stroke, it will be either 1 or 2 pulses per revolution. Seperate coils will probably be 1 per rev. A siemease coil (one coil w/two plug wires), probably 2 per rev. The instructions also say, efi is usually 2 per rev.

As for the pulse setting, even if you don't know what to set it to, the magnitude difference between settings is large enough, such that you could tell if you are getting reasonable idle rpm numbers.

Is the battery replaceable?

chavist93 said:

Is the battery replaceable?

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No, but it is only a lcd display, and being designed as an hour meter, suspect it will last a few years, but probably much longer.