could slight engine miss be related to a tach that dont work?

[jfrey8899]

Have a 1972 seaswirl with 140 mercruiser. Did compression check and replaced cap rotor plugs wires and new fuel tank and lines and rebuilt carb to. Still has very slight miss and read somewhere that it could possibly be related to the tachometer or rpm gauge. That is the only gauge on the boat that does not work. Could these two things be related somehow!? Is there a quick test I could do to confirm this

 

[ussoldier_1984]

Re: could slight engine miss be related to a tach that dont work?

I dont know on your year but on alot of mercruisers a bad tac can kill the ignition system and cause a motor to run bad or not at all disconnect the tac lead and see if it clears up the problem

 

[jfrey8899]

Re: could slight engine miss be related to a tach that dont work?

Tach leads. The connections on the back of the gauge. ?

 

[JustJason]

Re: could slight engine miss be related to a tach that dont work?

Yes, just pull the tach out and pull the "sense"wire off the back of it, make sure it's not grounded anywhere, just leave it open.

 

[Haffiman]

Re: could slight engine miss be related to a tach that dont work?

I would have disconnected the Gray wire straight on the coil.
That eliminates cable harness problems, than may even be the reason for tach not working.

 

[fishrdan]

Re: could slight engine miss be related to a tach that dont work?

72 SeaSwirl with a 140 HP Mercruiser? I had one of those, a tri-hull. The tach was dead on it also, but it wasn't causing any engine problems.

As the others have said, disconnect the tach sense lead to see if it changes anything.

Have you changed the points and condenser, set dwell and timing? My 140 had a bad distributor, bushings were shot causing erratic timing and an odd miss at idle. Sound familiar? Check to see if the distributor shaft has any play, off axis, left-right, forward-back. If you can feel play in the shaft, it's bad.

 

[jfrey8899]

Re: could slight engine miss be related to a tach that dont work?

Yes. All replaced. Cap rotor points plugs wires condenser. Timing was set. Don't have dwell meter yet. But it sounds great at idle. Just when on gas you really have to listen but its there. Very silght miss. Gotta be something with ignition. Compression check went great as well as carb rebuild. Got new fuel tank and lines to.