Tach reading only half RPMs on johnson GT150

[red10]

Well guys i haven't posted in a while ( which is good ), but i ran into a tach problem. The volts were reading 12-13 at wide open and the tach is dead, so i replaced the voltage reg. that fixed the charging issue but now the tach reads 2800 rpm when i know its around 5500. I have replaced power packs, coils, and plugs in the past. The boat gets out of hole fine and idles fine but the stator is showing some brownish junk running down the block, i'm planning on replacing it soon. Any ideas on the tach would be great since i'm lost.
Thanks

 

[clemsonfor]

Re: Tach reading only half RPMs on johnson GT150

interesting, my tac on mine will work, then drop to zero, and not work untill restart and it may work then drop back to zero, only to register again once it starts, i think mine is a loose wire, sorry im not asking for thoughs her i dont want to hijack your thread just curious on your answers. Oh and youll get bumped back to the top by this.

 

[red10]

Re: Tach reading only half RPMs on johnson GT150

no problem, i've been doing some reading on the tach issues and this one really has me confused, i have continuity on the wires and voltage, so its a challenge.

 

[petryshyn]

Re: Tach reading only half RPMs on johnson GT150

Sounds like you need a stator....The tach relies on the stator for its signal.

 

[countvlad]

Re: Tach reading only half RPMs on johnson GT150

no problem, i've been doing some reading on the tach issues and this one really has me confused, i have continuity on the wires and voltage, so its a challenge.

theres away to check make sure ur power pack that has a diode in is not bad... what you have to do is bypass the power pack and get the signal right of the stator.... here it is...

http://forums.iboats.com/showthread.php?t=190636

ive used to have a similar problem where my tach would drop over certain rpms and that was due to bad diode insede the power pack... good luck

 

[red10]

Re: Tach reading only half RPMs on johnson GT150

i'll have to try that stator test again and verify its accurate, the tach worked fine before the regulator went out so i know its not the tach, but i'm wondering if the stator is the problem.

 

[countvlad]

Re: Tach reading only half RPMs on johnson GT150

i'll have to try that stator test again and verify its accurate, the tach worked fine before the regulator went out so i know its not the tach, but i'm wondering if the stator is the problem.

12-13V sounds low i think you need about 13.5 14v .... dont check the voltage with the gauge.. they are not very accurate.... try to test with a meter across the battery terminals while the boat is idling and close to WOT see if theres a diffrence

 

[red10]

Re: Tach reading only half RPMs on johnson GT150

i used a meter across the battery, thats when i realized the regulator (water cooled 35 amp system)was shot.

 

[red10]

Re: Tach reading only half RPMs on johnson GT150

Well guys i replaced the stator and the tach still reads half, i didn't touch any settings on the back and it worked last fall with erratic readings here and there.

 

[countvlad]

Re: Tach reading only half RPMs on johnson GT150

Well guys i replaced the stator and the tach still reads half, i didn't touch any settings on the back and it worked last fall with erratic readings here and there.

so you replace the stator or the rectifier/regulator???

 

[red10]

Re: Tach reading only half RPMs on johnson GT150

i replaced both since there was the black junk running out on the block, this is a mystery, could the tach have been taken out by a bad regulator? The wiring is fine, i checked continuity.