Thermostat housing hole.

Douglasdzaster

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One, two and once every other revolution it's OK, that tach is missing half of the equation which is the number of cylinders the motor works with. That tach is useless. Return it to Amazon, tell them it's not for your type of motor and get the one posted above....

Happy Boating
Will have one here tomorrow that say it will work on 2 stroke 3 cylinder as well as others. Not the exact one you posted but from the same family.
 

Douglasdzaster

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Don’t know how I doubled up the messages but my new tachometer came in this evening. Got a bilge pump on the way which I should have already installed. Thinking I may make it out Monday if not sooner. Watching the weather.
 

Sea Rider

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Post a pic of the new tach, although there's so many available to choose from need to order the right one. Probably have seen the same offer, 2 for $ 19.95, if so, are only hour meters...

Happy Boating
 

Douglasdzaster

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Post a pic of the new tach, although there's so many available to choose from need to order the right one. Probably have seen the same offer, 2 for $ 19.95, if so, are only hour meters...

Happy Boating
F3C67BF1-BB35-4C1C-BA60-980A3814DFF4.png It’s got several settings including 2 stroke 3 cylinder . I just have to figure out the instructions. I messed with it for a few minutes earlier and couldn’t set anything. I’m going to study the instructions tonight instead of trying to rush through them.
 

Douglasdzaster

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View attachment 336302 It’s got several settings including 2 stroke 3 cylinder . I just have to figure out the instructions. I messed with it for a few minutes earlier and couldn’t set anything. I’m going to study the instructions tonight instead of trying to rush through them.
Ran the engine some with the new tachometer. It seems to work well. I’ll know when I get on the lake.
 

Douglasdzaster

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Which were the idle rpm shown in the screen ?

Happy Boating
Danced all around 800. I’d rev it a little and it would come down to around 780 or so then back to 800. I’m going to the lake tomorrow. I’ve lowered the trim by one notch which with the boat sitting level has it just a little low of 90 degrees. About the same as the upper notch putting the motor a little above 90 degrees.
 

Sea Rider

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Danced all around 800. I’d rev it a little and it would come down to around 780 or so then back to 800. I’m going to the lake tomorrow. I’ve lowered the trim by one notch which with the boat sitting level has it just a little low of 90 degrees. About the same as the upper notch putting the motor a little above 90 degrees.
In some boats it's near impossible for the motor to achieve exactly 90 deg at transom, if I had to choose prefer slight under than above 90 deg.

Happy Boating
 

Douglasdzaster

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In some boats it's near impossible for the motor to achieve exactly 90 deg at transom, if I had to choose prefer slight under than above 90 deg.

Happy Boating
I spent 5 hours on the lake today. This tachometer only shows 2700rpms at wot like the other one. All most 3000 at one point. I confirmed I had it set for 2 cycle 3 cylinder 5 wraps around the first spark plug wire still neat and tight.Motor was running good. According to the app on my iPhone I was doing 27 mph. Rough water. Wind blew harder than expected today. I was figuring around 30mph because I’ve watched a lot of videos of guys running 40 hp motors on boats smaller than mine and reaching 35mph and up. One guy hit 40. Mines extra wide and heavy. But sturdy I stopped in several places and caught some bass. The boat fished great in the rough water with the trolling motor on the bow. I still must have something set wrong. After fishing the motor was hard to start. Some times it would start and kick hard enough to turn the motor to the side then the rpms level down to idle and it would be okay. Occasionally idle rough. I went to the dock and tied off. With the motor idling I turned the first pilot screw 1/4 turn out waited a minute and no change so I went another 1/4 waited and still no change. Then I tried the same turning it in and still no change. Did the same thing with the other 2 pilots and no change the idle stayed a little rough. I shut the motor off and put all three pilots back to 1 1/2 turn out from bottom. Started first pull and idles smooth again. But every time I’d stop and fish awhile it would take several pulls and choking before it would start and it would have that one hard hit as soon as it starts sometimes killing the motor. Never a problem at wot all day though.
 
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Sea Rider

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Well that's an excellent run out of muffs. Does the tach counts with a 2 stroke, 2 sparks per revolution, 3 cylinder setting ? If not, set it to 2 stroke, 2 sparks prer revolution check if the wot rpm now reads full true wot rpm.

Right now the motor is slightly over revving from max 5500 wot rpm range factory stated, not an issue, just throttle bit less or add more load on board if like running full grip LOL!!

Sometimes when at a long water stop, need to follow the cold starting procedure to re start the motor up. Most 2 stroke motors does same. Will you be willing to go for a long CRC decarbon process through the carbs, if so, the motor will idle and run much smoother guaranteed.

Happy Boating
 

99yam40

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some of those inductive tachs have a problem with interference from the other spark plug wires .
also sounds like a lean sneeze happening that causes the motor to kick hard and die
 

Sea Rider

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some of those inductive tachs have a problem with interference from the other spark plug wires .
also sounds like a lean sneeze happening that causes the motor to kick hard and die
That's why need to route the signal pick-up cable straight from the tach to the spark plug cable with no cable slack., for that will need to trim the cable excess once conveniently routed. Have installed about 50 induction tachs over the years with no interference issues whatsoever. As of now, the tach is only reardng half of the achieved wot rpm.

Happy Boating
 

99yam40

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if that is a 3 cylinder motor then it is not a waste spark system so each plug should fire just once
 

Sea Rider

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if that is a 3 cylinder motor then it is not a waste spark system so each plug should fire just once
It's a 3 cylinder motor and if it's the case the OP will need to adjust the firing sequence to : 2 stroke motor, 1 spark per revolution and if reads true wot rpm will confirm it's a 1 spark per revolution setting ? If reads exact same, that tach model it's not 100% compatible for a 3 cylinder Yam motor.

Happy Boating
 

Douglasdzaster

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That's why need to route the signal pick-up cable straight from the tach to the spark plug cable with no cable slack., for that will need to trim the cable excess once conveniently routed. Have installed about 50 induction tachs over the years with no interference issues whatsoever. As of now, the tach is only reardng half of the achieved wot rpm.

Happy Boating
It’s set on 3p1r as per the instructions. The cable is ran straight down the opposite side of the rest of the plug wires, and coils, and all other electrical. I had my worries about it being close to the fuel lines but wanted away from any other electrical stuff. Here’s a picture of the different settings. Which one do you think I should try to get my true readings?AAB8B29C-3170-4980-958B-C5A98D9BC11A.jpeg
 
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Douglasdzaster

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some of those inductive tachs have a problem with interference from the other spark plug wires .
also sounds like a lean sneeze happening that causes the motor to kick hard and die
Thanks for the reply. I’ve just completely rebuilt the carburetors. All three pilots are open 1 1/2 turn. Should I open them another 1/4 or 1/2 and run it to see what happens? I’ve tried adjusting them with the engine warmed up and idling at the dock. I’d make a turn and wait a minute or so but couldn’t tell any difference in the idle so I put them all back to 1 1/2 but I still have that hard kick some times.
 

Douglasdzaster

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Got another question. I premix my 2 cycle fuel and I’ve been using Lucas semisynthetic in this older engine. How does it compare or what’s y’all’s opinion on it vs other brands?
 
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