115 Mercury ?'s Please help...

[hjsmith00843]

My tach is not working at all. When it gets to high RPMS it will jump around to over 6000 and down to 0. If I tap on the rectifier while idling I can see the tach jump a little. Does this sound like the rectifier is bad?
Another ? What is the baseline setting for the carbs on the needle? I went all the way in and 2 turns out. Motor sounds smooth and has alot of pickup on the hose. The needle settings were all over the place. From 1.5 turns out up to 3.5 turns out. :facepalm:


If it matters the motor is a 1987 model.

 

[Chris1956]

Re: 115 Mercury ?'s Please help...

Initial carb settings are 1/5 turns out from light seat. Recitifiers are usually good or not good. You likely have a bad tach or bad wiring.

 

[kvjimbo]

Re: 115 Mercury ?'s Please help...

Try tapping on the tach.

 

[Georgesalmon]

Re: 115 Mercury ?'s Please help...

Not unusual for each carb to have different settings for the needle, after all, the carbs and neddles are manmade and will have slight differences. Though, two full turns difference is a bit unusual. Good pickup on the hose does not tell you very much. Need to get out on the water to adjust that properly. Start at 1 1/2 out and see if you still get good idle.( two turns out might be very close to right but I'd still adjust them to be sure) At idle turn each needle in until the motor sputters and then back out until smooth. Turn very slowly, thats the initial setting. Then on the water accelerate and see if its OK. if not turn every needle out another 1/4 turn and try again. Do that until you get good acceleration, no bogging down, then leave them alone. Usually no more than 1/2 turn more out from the initial setting will do it, but every motor is a little different. Make sure the motor is all warmed up while doing any of this and make sure the carbs are clean inside if this procedure doesn't do it for you.