mercruiser ignition problems

bid2ask

Seaman
Joined
Nov 4, 2004
Messages
54
ok guys heres what i have its a 1986 mercruiser 140, with points ignition, i have a problem with keeping it running. it will stall out on me after a few minutes on the muffs at idle, @650 rpm., i did a complete tune up to see if that would help and its still dying out on me..if i take a wire from the +12 side of the battery to the + side of the coil it will run great, whats the best way to isolate whats wrong? i disconnected my temp wire as not to burn out the points with batt voltage. i also have a mercruiser resister kit installed in the harness going to the coil.
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: mercruiser ignition problems

Disconnect your boats fuel system at the engine fuel pump and hook up an outboard tank and see what it does.<br />You could have problems with the fuel pickup, the antisiphon valve, hoses sucking air instead of fuel due to bad hoses or wrong clamps, plugged fuel tank vents or low spots in vent hose.
 

bid2ask

Seaman
Joined
Nov 4, 2004
Messages
54
Re: mercruiser ignition problems

don, i cleaned the antisiphon valve, replced all fuel filters, installed a new factory mercarb, getting great fuel pressure, why is it if i hook up 12 volts to the plus side of the coil it runs better
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: mercruiser ignition problems

You also did a tuneup. After you changed the points, did you set the dwell, and then reset the timing and adjust the carb?
 

rattana

Chief Petty Officer
Joined
Jun 12, 2003
Messages
413
Re: mercruiser ignition problems

What is the voltage between the positive side of the coil and the block when it starts acting up?
 

Uncle Dave

Petty Officer 1st Class
Joined
Jun 10, 2003
Messages
240
Re: mercruiser ignition problems

You have made no mention of the coil. Did you change it. The coil is mounted close to the block and gets pretty hot after a few minutes. An intermitten coil will give you some similiar symptoms. If it is an 86 model coil it is due for a change. often mistaken for carb problems.<br />Uncle Dave
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: mercruiser ignition problems

You also need to check the resistance from the 'ON' side of the key switch to the coil "+". It sounds like you have a resistive wire going faulty. Does the engine slowly die out, or is running great then just die, like the key has been turned off?<br /><br />You say you have a restistive wire kit installed. Is this in series (in line) with the original or does it replace the original?<br /><br />Chris............
 

bid2ask

Seaman
Joined
Nov 4, 2004
Messages
54
Re: mercruiser ignition problems

Chris,it dies a slow, reistor replaces the original
 

bid2ask

Seaman
Joined
Nov 4, 2004
Messages
54
Re: mercruiser ignition problems

thanks guys it was a bad coil, replaced it today it runs great now
 
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