Background info: 87 Mercruiser 454/330hp Alpha 1 outdrive, Thunderbolt IV with no plug, wires come directly out of module on portside riser. Fairly low hours, estimate under 3-400, have had the boat in the family since new. Has always been properly winterized/layed up including oil changes, stabil in gas, and drain block/filled with antifreeze.
On summerization, after installation of a new battery, started easily on the muffs, but ran very rough.
So now, done in this order:
Fuel system
Completely drained fuel tank
Changed fuel filter/water separator
Had Rochestor 4B carb boiled/rebuilt at carb shop
Ignition system Parts from EBASICPOWER
Replaced cap/rotor/ignition sensor in distributor(new style sensor, non metallic, has green/white, red/white and ground leads with bullet connectors and ring terminals to connect with original ring terminal wires
Replaced coil (original was leaking oil)
Replaced plugs/wires, wires were original
Checked ignition timing with timing light, it is spot on, with original timing marks, (I believe to be 6BTDC?)
Have been through the flow chart diagnostic testing for the Ignition Module, everything tests out within specs.
Boat starts on the muffs without problem, but runs very rough most of the time. I played with the shift interupt switch, thought that it was bad, as I could get the boat to run smooth at times by wiggling the switch. So I disconnected it completely (Green/white wire) to rule out. This did not fix the problem. I then tried intermittantly grounding the green/white wire and get the boat to smooth out temporarily.
I have also tried disconnecting the main engine harness, and ran the boat with 12v to coil + and jumper wire to start. It runs just the same with no difference in smoothing out, kinda coughing all the time. It is getting plenty of fuel, plugs are black and wet.
After all of the above, the boat does not run consistently any different than when I started out. I think it has to be electrical, as it does respond as noted above with playing with the green/white wire to ground. I have checked + and - connections all over the boat, everything is good and tight, with no corrosion.
I am stumped, where/what should I go after next?
What else can I try? Can the ignition module fail intermittantly? I didn't think so, but obviously, I am missing something.
On summerization, after installation of a new battery, started easily on the muffs, but ran very rough.
So now, done in this order:
Fuel system
Completely drained fuel tank
Changed fuel filter/water separator
Had Rochestor 4B carb boiled/rebuilt at carb shop
Ignition system Parts from EBASICPOWER
Replaced cap/rotor/ignition sensor in distributor(new style sensor, non metallic, has green/white, red/white and ground leads with bullet connectors and ring terminals to connect with original ring terminal wires
Replaced coil (original was leaking oil)
Replaced plugs/wires, wires were original
Checked ignition timing with timing light, it is spot on, with original timing marks, (I believe to be 6BTDC?)
Have been through the flow chart diagnostic testing for the Ignition Module, everything tests out within specs.
Boat starts on the muffs without problem, but runs very rough most of the time. I played with the shift interupt switch, thought that it was bad, as I could get the boat to run smooth at times by wiggling the switch. So I disconnected it completely (Green/white wire) to rule out. This did not fix the problem. I then tried intermittantly grounding the green/white wire and get the boat to smooth out temporarily.
I have also tried disconnecting the main engine harness, and ran the boat with 12v to coil + and jumper wire to start. It runs just the same with no difference in smoothing out, kinda coughing all the time. It is getting plenty of fuel, plugs are black and wet.
After all of the above, the boat does not run consistently any different than when I started out. I think it has to be electrical, as it does respond as noted above with playing with the green/white wire to ground. I have checked + and - connections all over the boat, everything is good and tight, with no corrosion.
I am stumped, where/what should I go after next?
What else can I try? Can the ignition module fail intermittantly? I didn't think so, but obviously, I am missing something.
