Thread: 4stoke question

Should of listened to Tex. Tach read 2700 at WOT. I had set for 1 spark/rev. Obviously it was off by factor of 2. So I set for 1 spark/2 revolutions and will try tomorrow. Also put SS prop on to test.

I'm waiting on your post. I received my TT2AM in the mail yesterday and will install it today on my 40 hp Tahotsu 2017 model. I am confused on the spark setting also but the fellow at Tiny Tach said to install the red wire around the bottom spark plug wire. I tried the new 11x13 SS Prop last week and didn't notice any difference from the 11x14 aluminum prop.

Well I can't get mine to read correctly. Shouldn't matter which plug it is on since it be it's counting sparks.
Set at 360° it is reading 1spark/revolution. It was reading half of what it actually was turning but it seemed pretty accurate.
When I set it to 720° it bounced all over the scale.
I'm going to need a higher pitch than 13" . At 28-30MPH I think I was around 5500-6000 RPMs. With the 15" aluminum it runs around 35MPH at 5600.
I'm not looking for more speed, I needed the SS for some if the flooded forest I fish.

The erratic readings are more likely to be a wiring problem then a setting problem. I’d double check your wraps on the plug wire and make sure they’re good and tight and that the wire is running as far as possible from the other plug wires and coils to be sure you’re not getting interference from them. Also make sure you have a good ground connection, a bad ground will definitely cause problems.


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Originally Posted by Tex_79

The erratic readings are more likely to be a wiring problem then a setting problem. I’d double check your wraps on the plug wire and make sure they’re good and tight and that the wire is running as far as possible from the other plug wires and coils to be sure you’re not getting interference from them. Also make sure you have a good ground connection, a bad ground will definitely cause problems.


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Agree. I'm going to recheck everything.

Got to try my tach today and it worked fine set at 360* 1 spark per revolution. I didn't get a WOT reading the canal was to short on streightaways and to many cypress trees, 3/4 throttle read 4000-4200 rpm's which seemed about right. For a fishing report I got skunked, gonna go to the river Wednesday for a better test.

Thanks. Set at 360° mine reads fine at idle but maxes out at 2700 at WOT.
Set on 720° it bounces all over at idle, 800-200 RPMs.
Gonna recheck wiring and maybe put a pice of tape over wire wrap.
After talking to dealership they think a 15 SS prop will be fine the boat only weighs 600# without motor, batteries,etc.

I got to test mine again yesterday, WOT showed 5870 rpm's with the 11x13" prop. What I'm finding strange is I reach that rpm at 3/4 throttle and when I turn the throttle the rest of the way there is no change in rpm's. This is my first 4 stroke engine and have only 2 stroke motors to compare to. Top speed was 30 mph on my phone. I'm thinking I should have gone with a 14 or 15" prop