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Old 10 September 2014, 03:09   #1
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Tiny Tach on Tohatsu 18 hp

I just bought a Tiny Tach for my Tohatsu 18 hp 2 stroke. Does anyone know what the setting sould be ie. 360 deg, 180 deg or some other setting.
The manufacture recommends 360 deg. I find that the revs shown are too high. So I have selected 180 deg.
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Old 11 September 2014, 20:30   #2
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Ok. Looks like nobody uses the Tiny Tach. So does anybody know what rpm the 18 hp Tohatsu idles at. This will help me set the Tiny Tach correctly
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Old 11 September 2014, 21:22   #3
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Ok. Looks like nobody uses the Tiny Tach. So does anybody know what rpm the 18 hp Tohatsu idles at. This will help me set the Tiny Tach correctly
Hi

I would have thought 4500 to 5500 rpm and idle would be 750 to 1000 would be about right.Not 100% on your rev range though.
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Old 12 September 2014, 07:29   #4
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After all else fails, read the manual. The manual advises idling revs while stationary to be 950 rpm and 800 rpm while in gear.
Now I wish I new someone with this tach and an 18 hp Tohatsu. I am getting different advice on settings from people who should know.
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Old 12 September 2014, 10:09   #5
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Tiny Tach on Tohatsu 18 hp

Hi,
The manual for the 9.8 Tohatsu states idle rpm 950 out of gear and 750 in, and 5 - 6000 full throttle range. The 18 is probably similar.
I have a cheapo tach similar to a Tiny Tach and this is set to 02 (once per revolution).
To be honest it's fairly easy to tell if setting is wrong as the revs are either double or half what they should be😎
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Old 12 September 2014, 18:18   #6
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One of you 2-stroke guys correct me if I'm way off base here - I seem to recall hearing of some 2-strokes set up like this:

I believe you may have a motor that fires every revolution of the crankshaft, but the spark plugs share the same feed (i.e. each plug is firing twice per revolution.)

If that's the case, you'd need to set the TT to 180 degrees (I think.)

jky
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Old 12 September 2014, 22:26   #7
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Yes with the Tohatsu 18 hp 2 stroke I have set the TT to 180 deg. My engine was idling a bit high I think, so I adjusted the idle down a bit. Now using the 180 setting the TT displays engine idling at 950 - 1000 rpm. Sounds about right (I think) but it would be nice if someone with a setup similar to mine could confirm.
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Old 13 September 2014, 03:09   #8
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I believe you may have a motor that fires every revolution of the crankshaft, but the spark plugs share the same feed (i.e. each plug is firing twice per revolution.)
= "Lost spark"
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Old 13 September 2014, 03:42   #9
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Just try the different settings until it looks right, I've got one on my tohatsu 50 and it works great. can't remember the setting but I just fiddled around until the revs were about right. The other two settings will give completely different revs
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Old 13 September 2014, 14:53   #10
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= "Lost spark"
I think it was done for simplicity. Didn't have to engineer 2 separate spark circuits.

jky
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