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Discussion Starter · #1 ·
I got a merc 70 horse on the boat i just bought. It is a 3 cylinder 2-stroker. The guy i bought it off of just changed the tach before he sold it and said he wasnt sure if he had it set up properly. I took it out for a spin and at first the tach showed idle at a healthy 1000rpm. But as soon as a dropped the hammer, the tach spun right around past 6000rpm. The motor didnt sound as if it was over-revving or anything and ran very well. Once i let off, the tach showed idle at 2300rpm.

There are a number of settings on the back of the tach, each labeled with number of cylinders and a pulse number. There is no 3 cylinder setting on it and i have no clue what the pulse number means.

Any help is much appreciated, chances are if I cant figure it out, I'll end up on a lake switching settings and runnin the motor to find out.

Thanx


Bill
 

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I can't help you on the tach settings. I don't have them in my boats. But 2300 rpm seems a WEE bit high for an out board. I will have to verify, but on my Johnson 60 hp, idle is something like 700 rpm.

You might need to look online for setup directions directly from the manufacturer. Or you could try www.iboats.com

This site sells boats and boating accessories. There is also a boating forum.

Good luck.
 

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I have the same motor it has a serious flaw with the electrical system .It has little to no overvoltage protection I found this out the hard way out on the water I noticed the voltage was 17vdc and by then it was too late the whole elec system was cooked I researched this and found it found was a common issue with this motor and merc.made a kit called the red stator retrofit it cost me about 700 bucks doing the work myself search red stator retrofit i am sure you will find plenty of info
 

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Discussion Starter · #4 ·
I went to a boat dealer today and one of the techs said the proper setting was 6 pulse. What year motor is yours deuce? Mine is a '95 and I hope mine isn't affected, but I'll have to look into it anyway. Getting stranded in the middle of Lake Superior doesn't really sound like fun to me!

Thanks for the info guys!
 

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Snowforce21 said:
I went to a boat dealer today and one of the techs said the proper setting was 6 pulse. What year motor is yours deuce? Mine is a '95 and I hope mine isn't affected, but I'll have to look into it anyway. Getting stranded in the middle of Lake Superior doesn't really sound like fun to me!

Thanks for the info guys!
1990 I was two miles from home no big deal great lakes would be a big deal,The updated motor has a huge voltage regulator mounted on a huge heat sink over the air box.
 
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