OX66 no TACH signal

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phothkia

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Jun 15, 2014
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Long time reader...first time poster. Thanks for all the info in the past, hopefully someone can help!

Engine: 2000 SX225TXRY (OX66) hooked up to a Yamaha multifunction digital tach.

Backround: New powerhead installed by a Yamaha Master Tech....zero RPM readout on tach. BTW, the first replacement powerhead had saltwater intrusion into a couple pistons within 3 hours of the proper break-in period and was sent back under warrantee, but during those three hours the RPM readout on the TACH was working fine. I was conservative during the break-in period without a tach readout on this powerhead, and the engine has been functioning fine for the first 12 hours. Need to get the RPMs on the tach working because I suspect I am over propped and because I will accept nothing less!

Indications on the TACH: Oil level indications on the tach have been tested and are working fine. The hour counter on the tach DOES NOT count up (stuck at 190 hours...from when the tach was new). RPMs reading ZERO at all throttle settings. I'm guessing two issues are related...the hour counter requires RPM to register before it will start counting engine hours.

Troubleshooting thus far (with Master Tech):
1. Checked continuity and ohms from the TACH green wire all the way back to the green CDI output pin....all showing normal.
2. Hooked up new TACH to a dummy harness/ignition connected at the engine...TACH showed ZERO RPM...thus eliminating faults from the boat TACH all the way back to the engine harness.
3. No AC voltage coming from the CDI green wire output to the TACH (tested just short of the TACH...after continuity/resistance was verified)
3. Tested crank position sensor for voltage output to CDI (although I don't know if this sensor is what provides the CDI with the information to send to the TACH)
4. Tested THREE OTHER CDIs (after assuming that was the problem)....all registered ZERO RPMs to the TACH.
5. Yamaha Speedometer shows voltage increase when the engine is running (from about 12.4ish to 13.8ish), so I'm assuming the charging system is working fine.

What I would like to know:
1. Where does the CDI obtain the RPM information to send to the TACH? Crank Position sensor? Voltage Regulator/Rectifier? Stator? Other?
2. Am I missing a troubleshooting step? At this point if the wiring from the CDI to the TACH is fine, and four different CDIs are all failing to send a signal to the TACH, and two different TACHs show ZERO rpms...I can only assume that there is an input signal to the CDI that is not occuring, thus no output signal.

Thanks all, I look forward to your expertise. Additionally, I have combed the internet fairly thoroughly and did a search on this forum, so if this issue was already brought up, solved, and posted....I would appreciate a point to the correct thread.
 

m0rt3nlund

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Aug 6, 2016
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Hi! Did you figure this out? :) I have the exact same problem and have done the same troubleshooting as you have without any result..

Hope to here from you!

Morten Lund
 

GA_Boater

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m0rt3nlund

You won't hear from the OP. He left for vacation on June 17, 2014. Must be stranded on a South Sea island because he never returned . Read the Help Tip on top of the page and start a new thread.

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