bouncing tach '94 Johnson 90HP

[karma]

ok guys, the tach on my boat seems to work fine alot of the time, but from time to time bounces up and down like its losing power. where do i start to look for the problem? ive seen other posts that talked about a rectifier, but im not sure what or where that is. thanks in advance for your help.

 

[OBJ]

Re: bouncing tach '94 Johnson 90HP

Hi karma.<br /><br />First check the tachs connections. Make sure they are secure. The lead to the tach for signal will be the gray wire. The purple wire is the "hot" wire from the ignition. Black is ground. Let me axe ya' a question or two. What type of control do you have, is it a flush mount or box on the side of the gunrail? If it is a side mount, the tach is fed from a plug at the bottom of the control box under the key swithch. This may be a little lose and loose contact momentarily. If it's lose, take a wire wrap and put around it and snug it up. Should take care of the problem. Sometimes the tach acting erratic is a signal that the rectifier/regulator is about to die. Let us know what ya find and we'll go from there. Thanks.

 

[DIRTPOORE96]

Re: bouncing tach '94 Johnson 90HP

Hi Karma, it could be your rectifier, but there are other things that need to be checked also. The rectifier will effect the tach, but will also set off the oil warning horn. Is your battery charging while the engine is operating? When the rec. goes bad it will not charge the battery. Check battery voltage with engine running.

 

[karma]

Re: bouncing tach '94 Johnson 90HP

thanks for the quick reply guys, the tach is a flush mount. the oil warning horn hasnt gone off at all and the battery is charging. ill check the connections when i get home tonight and let you know what i find.<br />thanks again...karma

 

[Jerry M.]

Re: bouncing tach '94 Johnson 90HP

Karma, not sure your J is the same as my Merc, but on mine the tach wire comes from one side of the rectfier. A few weeks ago, my tach was also jumping, and after a while, the Volt meter showed no charging, and the tach went dead. Blown rectfier. As I understand the way it works, the rectifier changes the AC coming from the stator to 14 volts DC. <br /><br />Jerry