Mercruiser 350 MAG Bravo starting issue - very strange

Hi everyone,

I have a very strange starting issue that started a couple of months ago.
When I turn the key, the starter engages for a sec or two and disengages, then re-engages, then disengages. Most times the engine will kick into life and runs perfectly.

I thought the starter solenoid may be on its way out, so swapped the starter motor complete out. no change.
I cleaned all terminals and replaced battery. No change.

I changed the ignition barrel... no change.

through fault finding I removed the plug from the ECM and she turns over perfectly (but obviously wont run).

any ideas at all? am I up for a new ECM? I dont want to drop $1000 on a new one to find out its actually a signal to the ECM thats the issue.

Starting circuit is not tied into the computer in most cases .MPI motors have the solenoid circuit involved with other systems Without a year or engine serial number ,were just guessing

Hi,

The Engine number is 1A054175. 2007

jimlee43 said:

through fault finding I removed the plug from the ECM and she turns over perfectly (but obviously wont run).

Click to expand...

what does "remove the plug" mean???

Only thought that comes to mind is the ground side of the slave solenoid has a marginal path to ground...may be useful to probe voltage there during cranking w/ & w/o the "ecu plugged in"...

makomark said:

what does "remove the plug" mean???

Only thought that comes to mind is the ground side of the slave solenoid has a marginal path to ground...may be useful to probe voltage there during cranking w/ & w/o the "ecu plugged in"...

Click to expand...

Got to the bottom of it.
the cable at the back of the starter solenoid was corroded. the insulation block had started to melt.
Made up a new one and she is all good.

thanks to those that responded.

Thanks for closing out the thread with the fix