85 Johnson 150 GT Tach/Rectifier troubleshooting

[jskise3]

Tryin to get my tach back in working order before i replace the prop and change size. I got 12V behind the tach so i thought it must be my rectifier. Before starting the boat the battery reads 12.5V, after running about 5-10 minutes the battery reads 13.5-14.0 volts, leaving the voltmeter hooked up and reving the engine the battery jumps to 14.5-14.7 volts. So I am assuming that the regulator/rectifier is still good. What now? The needle stays on 3k rpms. I have an old
80's auto tach. Can I hook that up just to see if there is some kind of signal so i know to buy a new tach?

Also I have my fuel gauge working, I know the sender is bad on the trim its on the way. But I need a detailed description on where the water inlet is on the speedo. I blow on the 90 degree fitting and the needle jumps. Pitot must be clogged but I dont know where to clean? The place I thought shoots water out when the motor is running. I cant find the pitot hole anywhere?

 

[jskise3]

Re: 85 Johnson 150 GT Tach/Rectifier troubleshooting

The 12 V is when the master switch is on reading from the white wire to the red wire. Anyone know what the colors are? There is red, straight across is a white with stripe dashes, in the middle is black and the top corner is a white?

 

[jskise3]

Re: 85 Johnson 150 GT Tach/Rectifier troubleshooting

well the auto tach jumps when the key is turned but there is no reading... don't know if it wouldnt read anything anyway (im guessing not). I'm thinkin its my tach that is shot. Any education would be nice; never worked on boats before, Im kinda troubleshootin in the dark.

 

[emdsapmgr]

Re: 85 Johnson 150 GT Tach/Rectifier troubleshooting

From your description, the combination rectifier/regulator is working properly. That is the device that sends the signal to the tack. Should work. Maybe the tach is bad. A marine tach is not the same as an auto tach-you are better off to try to borrow another marine tach for testing purposes. Your speedo pickup is on the leading (knife edge) of the lower unit. Run your hand up/down on that front edge. When you feel a burr, that is the hole for the speedo. Probably is full of wood, leaves from the lake. Use a very small drill bit and wiggle it around with your fingers to get the debris out of that pickup hole.