1996 75hp Force Tach Jumping

[zach04071]

Hello,
I was out on my boat tonight and I noticed that when I was running at Wot the tach would jump from 5200 to about 6000 when I hit the trim button. The motor was not cavatating at the time. I also noticed that the fish finder kept turning off and I have had problems with the radio cutting out in the past. I have been chasing a problem with the motor where it will run erractly and the RPM will flucuate from around 5000 to 5200 which you can hear and feel in the boat. I replaced the line from the tank and also the connections on the tank tonight and that seemed to smooth it out. I have replaced the plug wires, cleaned the carb, replaced fuel lines and filters. Any suggestions would be helpful.

Thanks,
Zach

 

[celtic gelf]

Re: 1996 75hp Force Tach Jumping

check or test your voltage regulator and leads...on the 150 the grey wire is my tach wire coming off it...plus I had a melted wire on the side of the coil packs that wasn't tied away from it....this contact would cause it to rev not rev depending on the moment in time...

 

[fucawi]

Re: 1996 75hp Force Tach Jumping

whilst it could be a problem in the live feed also check the earth wire is good as it is affecting both instruments....simplest way is just a tempary length of new cable and a test run

 

[TwoFish]

Re: 1996 75hp Force Tach Jumping

I had my tacho read high on occasions without the revs changing. It turned out to be some corrosion in the main loom plug at the rear of the engine on the starboard side of the sparkplugs. I cleaned up the corrosion and used non conductive grease to help stop the corrosion and it has fixed the problem.

Hard to know your problem is as the motor is changing revs. It could all be related or two separate problems. Fuel or electrics for the motor as fucawi suggests and a corrosion problem for the tacho. I have read somewhere where corrosion can lead to extra signals being sent to the tacho making it read high.