140 merc starts intermitently

[123coaster]

Help<br />I recently bought a 78 grew 164 with a 140 merc i/o at an auction the boat wa always stored inside and is in excellent conditon It has a new coil, spark plugs, points & condenser, rotor & distributor cap & sparkplug wires.<br />I took it for one ride and noticed that the motor would stumble when cutting back on the throtle i thought that maybe since it had been winterized and not run this year that it was just burning off the engine fogging.I traillered the boat home and parked it.The next day I took it out again I launched the boat then tried to start it. The engine turned over well and there was spark and gas at the carb but I could not get it to fire up. I took the boat home and changed the plugs and coil to see if it would give a stronger spark I gapped the points @ .16th the dwell was 29 degrees adjusted the timming to 6 degrees and the boat started.<br />I tried starting it about 5 or 6 times with no problems and a smooth idle.<br />the next day it would not start.<br />when i check the voltage at the coil it reads 12 volts on one side and 9.5 on the other is there has to be something I'm missing .<br /><br />i read in one of the merc 3.0 ltr forums about a throtle switch that cuts the spark when changing gears from forward to reverse but idont see one on the carb.<br />any ideas or help would be appreciated

 

[ron7000]

Re: 140 merc starts intermitently

moisture under the distributor cap?

 

[123coaster]

Re: 140 merc starts intermitently

I wiped the distributor cap and rotor with isopropyl alchohol did'nt work

 

[HULKSTERUPS]

Re: 140 merc starts intermitently

Try taking off the gray wire from the coil,I think it controls the tach.

 

[rodbolt]

Re: 140 merc starts intermitently

you were on the right track.<br /> the voltage on the - side with the points open should be 10.5 to 12 with points closed it should be 0. if the points are closed and you have a voltage reading your contacts are dirty or the points are not grounded. points are just a mechanical on off switch.<br /> good luck and keep posting

 

[HULKSTERUPS]

Re: 140 merc starts intermitently

What happen 123 coaster?

 

[123coaster]

Re: 140 merc starts intermitently

Hi sorry i took so long to get back I had to work a couple of 12hour shifts.<br />This morning I tried staring the motor it would turn over but not start so i did what Hulksterups suggested and removed the extra wires coming from the negative terminal on the coil (One grey for the tachometer and one brown for the interupt switch) and the motor started.<br />I removed the interupt switch and inspected cleaned and tested it with an ohm meter and found nothing wrong so I continued to follow the wire down to where it was grounded and cleaned it up and tried starting it with all wires on the coil it would'nt start.<br />I then pulled the wire off of the back of the tachometer and tried to start it again and the boat started. After it was running I connected the tach wire and the engine stayed running the tach perfomed normal an idle of about 600 rpm.<br />I shut the motor off and tried starting it and it would'nt start so i removed the tach wire again and it started.<br />I"m thinking that the tach seems like the problem but I was under the impression that when a tach fails it does'nt work anymore?<br />I will try another tach but this one seems fine when the motor runs , I'm starting to think that it might be coincidence and some other component say maybe the coil or condenser even though they are new might be failing.<br />I did at least have the boat out today in Midland Bay and the engine ran fine.<br />Let me know