Johnson 60hp to Yamah 90hp tach help, 7000rpm system check

[199675hpforce]

Ok im trying to figure out why my new to me boat's tach non functioning. I see some wires under the dash black with small ring around it and purple wire, plus couple cut wires. Did some reasearch late last night but couldnt save the page. Had wiring diagram for johnson system check. Shows grey wire being send,power plus ground. That's all I would need to get functioning tach right. On back of tach has dial 5 or 6 one being 2stroke I guess and other 4stroke johnsons. One of my problems is the maze of wires under the dash crazy and hard to follow. I might yank stereo out to help make room. Any suggestions? Should I check regulator first with my little volt tool, how do I set this up for ohm check. The only usable picture is tach others are tilt gauge and crap cant seem to delete them.

[boobie]

Are you trying to use a Yamaha tach on a Johnson ?

[199675hpforce]

Yes the johnson blew up from what guy told me and replaced with used yamaha 90hp

[patrick4266]

i am using a yam tach with a evinrude motor. Had a 50 yam motor, changed to a 70 rude and used the yam tach. You may have to pull out the tach and figure out the wires.

[boobie]

Is it a Johnson 2 or 3 cyl ( a model # would help). Depending on the mtr the tach could be set on either 5 or 6 pole position. The tach impulse comes off the gray wire and you need a power source and grd.

[199675hpforce]

Just got out from dash to have better look. I think the old harness and new harness are there. There is 8 pin harness with yellow,red,black,green wire I think from yamaha harness. The yellow has been tapped for other gauges. Being the tach lights do there thing when starting im guessing it hooked up for some reason. Do you know which wires are powering tach system check is it purple wire or two wires on top section of tach one black other blue or is this for tach lights something. I ask because there must be a ground already for those red lights to come on right. Maybe all I need to hook up is grey to green wire, if that doesnt work add ground to harness from omc tach, maybe hookup that purple comming out to red on yamaha? Im trying to trace how the old harness was terminated I wouldnt want a live wire hitting the hull somewhere down line. Also how come the grey sending wire splices what else uses sending pulse on dash.