"I have a 1975 Trojan with a t
"I have a 1975 Trojan with a twin Mercruiser 233HP 351 Ford Engines with Prestolite ignition. Before I pulled the boat for the winter, I was experiencing starting problems with my starboard engine. I would have to keep the starter engaged and pump the throttle until the engine eventually started. Once started the engine would begin missing when throttled up beyond 2000RPM. Once I pulled the boat I can't get the engine started to winterize it. I have tried the following lengthy diagnostics:
Replaced: Spark plugs (set@ .30), wires, distributor cap, rotor, coil and gas filter and water separator. Fuel pump was replaced 5 years ago. I rebuilt the carb and had the same problem. I swapped the port carb with the rebuilt and had the same problem. I ran a portable tank with fresh gas and had the same problem. Looking into the barrels of the carb, I can see I am getting gas while engaging the throttle.
I checked the timing by aligning the timing marks at 10 degrees BTC with #1 cylinder in the up position and the rotor aligns with #1 position on the cap. I removed the spark plugs, turned the engine over and all spark plugs were firing. Because the engine would occasionally backfire while trying to start, I loosened the distributor and tried to start it in different positions but no luck.
I performed a compression test and got the following results which I don't think would impact starting:
Cyl Dry Wet
1 125 140
2 120 135
3 140 150
4 130 140
5 135 145
6 135 145
7 135 145
8 140 150
The only thing that I am thinking now is that I may have a vacuum leak that is preventing enough gas to be sucked into the cylinders but I don't know how to test for this without the engine running.
I have reached the end of my rope and would welcome any suggestions."
"I have a 1975 Trojan with a twin Mercruiser 233HP 351 Ford Engines with Prestolite ignition. Before I pulled the boat for the winter, I was experiencing starting problems with my starboard engine. I would have to keep the starter engaged and pump the throttle until the engine eventually started. Once started the engine would begin missing when throttled up beyond 2000RPM. Once I pulled the boat I can't get the engine started to winterize it. I have tried the following lengthy diagnostics:
Replaced: Spark plugs (set@ .30), wires, distributor cap, rotor, coil and gas filter and water separator. Fuel pump was replaced 5 years ago. I rebuilt the carb and had the same problem. I swapped the port carb with the rebuilt and had the same problem. I ran a portable tank with fresh gas and had the same problem. Looking into the barrels of the carb, I can see I am getting gas while engaging the throttle.
I checked the timing by aligning the timing marks at 10 degrees BTC with #1 cylinder in the up position and the rotor aligns with #1 position on the cap. I removed the spark plugs, turned the engine over and all spark plugs were firing. Because the engine would occasionally backfire while trying to start, I loosened the distributor and tried to start it in different positions but no luck.
I performed a compression test and got the following results which I don't think would impact starting:
Cyl Dry Wet
1 125 140
2 120 135
3 140 150
4 130 140
5 135 145
6 135 145
7 135 145
8 140 150
The only thing that I am thinking now is that I may have a vacuum leak that is preventing enough gas to be sucked into the cylinders but I don't know how to test for this without the engine running.
I have reached the end of my rope and would welcome any suggestions."