I am over a week into this now and I am running out of ideas.
I have a mercruiser 228 MCM with a Holley 4 barrel and a Pentronix ignition module. When I am under load the motor pops back through the carb at around 2500 rpm. Sometimes it can go to 3000 before it pops. I can red line the engine in neutral. It sounds good in neutral.
Things I have looked at.
Compression Low 145 High 160
Timing is 8 deg at idle. Idle speed is about 700 rpm
Change rotor, cap, spark plug wires
Checked fuel filters and lines I put a section of clear tubing in the fuel lines and had no air bubbles when the engine was popping.
Tonight I used an advance timing light with the following light. All was done under no load because I was the only one on the boat.
idle 8 deg
1000 rpm 5 deg advance
1500 rpm 11 deg advance
2000 rpm 13 deg advance
2500 rpm 15 deg advance
3000 rpm 18 deg advance
3500 rpm 19 deg advance
At 3500 rpm the timing mark moved about 2 degrees each direction when watching it with the light on it. All other rpms stayed still. Does this mean my distributor is bad? Or is it the timing chain? I was thinking maybe I had a torn diaphragm on the carb pumps. Should I look at them as well?
Thanks for the help
I have a mercruiser 228 MCM with a Holley 4 barrel and a Pentronix ignition module. When I am under load the motor pops back through the carb at around 2500 rpm. Sometimes it can go to 3000 before it pops. I can red line the engine in neutral. It sounds good in neutral.
Things I have looked at.
Compression Low 145 High 160
Timing is 8 deg at idle. Idle speed is about 700 rpm
Change rotor, cap, spark plug wires
Checked fuel filters and lines I put a section of clear tubing in the fuel lines and had no air bubbles when the engine was popping.
Tonight I used an advance timing light with the following light. All was done under no load because I was the only one on the boat.
idle 8 deg
1000 rpm 5 deg advance
1500 rpm 11 deg advance
2000 rpm 13 deg advance
2500 rpm 15 deg advance
3000 rpm 18 deg advance
3500 rpm 19 deg advance
At 3500 rpm the timing mark moved about 2 degrees each direction when watching it with the light on it. All other rpms stayed still. Does this mean my distributor is bad? Or is it the timing chain? I was thinking maybe I had a torn diaphragm on the carb pumps. Should I look at them as well?
Thanks for the help
