Tach problem .

[rob 135]

I have 1973 Johnson 135, on a 1979 silverline tri hull. my problem is tach doesn't read right and won't go over 3 grand. This is second tach and same results. Both set for 12 pole . Checked AC voltage on gray wire , has around 10 volts . Engine runs 33 mph on gps . Battery charges fine 13 volts at idle and goes up from there. I would think at 33 mph would be over 3 grand . Any help please .

 

[Barnacle_Bill]

Is the tach supposed to be set for poles or pulses? Pulses are the most common and yours should be set to 6P.

 

[rob 135]

It's a teleflex tach had 4,6,8,10,12 pole settings. Have tried in all other settings just to see results . One tach I tried was a faria model set to 6 , stil same damn results.

 

[rob 135]

It's a teleflex tach had 4,6,8,10,12 pole settings. Have tried in all other settings just to see results . One tach I tried was a faria model set to 6 , stil same damn results.

 

[emdsapmgr]

Bad rectifier?

 

[rob 135]

It's new and charges fine. What should AC voltage be at tach grey wire?

 

[emdsapmgr]

What pitch prop are you running?

 

[rob 135]

17 pitch /13 in... motor sounds like it's turning up , but I could be wrong .

 

[emdsapmgr]

I would agree that a 135 with a 17 pitch prop would be turning well over 3000. Maybe 5500. So, it's probably propped close- those tri hull boats were heavy hulls. How old is the rectifier on the engine? I've seen all types of problems with them, including functioning properly at lower rpm's, then dropping out at higher rpm's. I replace the rectifier on my 70 for that very reason. The tach would drop out at higher rpm's. The new one fixed the problem.

 

[rob 135]

Do u think testing rectifier will show anything? Was new 1 year ago. It charges great