Any ideas appreciated....
In the water the engine starts up, idles and runs well when placed in gear up to 1500 rpm. Advancing the throttle above 1500 rpm the engine bogs down and will die IF choke is not applied. With choke applied the engine will catch and accelerate to WOT. Once at the higher rpms the engine runs perfectly for extended periods of time.
The problem first began after uncovering the boat from a four year storage so immediately I suspected varnished carburetors. I have executed the following work with no luck in solving the problem:
1. Carb rebuild w/ complete kits (floats included). Welch plugs removed, idle transfer circuit orfices probed with wire and verified clean. Carb cleaner and compressed air flushed through entire carb. Low speed and high speed jets are perfectly clear.
2. Verified that the timer base is NOT sticking
3. Replaced all fuel lines within the engine (from fuel pump to carb distribution). Checked screen on fuel pump to verify it is clear.
4. Had a friend operate the boat while I pumped the primer bulb. No change.
5. New plugs, gapped properly
6. Removed head, new head gasket
7. Verified all reed valves are functioning properly
8. Replaced intake manifold gasket
9. Verified all throttle plates open and close together
10. Executed lync'n'synch making sure the throttle plates do not open before the timer base advances
11. Verified the plastic sleeve on the carb linkage is 3/8" in diameter and in place
I have not rebuilt / replaced the fuel pump, but I find it hard to believe it is bad since the engine runs well at WOT. Could the pump be bad??
I am really stumped at this point and am hoping one of you sees something I missed. Thanks in advance!!
In the water the engine starts up, idles and runs well when placed in gear up to 1500 rpm. Advancing the throttle above 1500 rpm the engine bogs down and will die IF choke is not applied. With choke applied the engine will catch and accelerate to WOT. Once at the higher rpms the engine runs perfectly for extended periods of time.
The problem first began after uncovering the boat from a four year storage so immediately I suspected varnished carburetors. I have executed the following work with no luck in solving the problem:
1. Carb rebuild w/ complete kits (floats included). Welch plugs removed, idle transfer circuit orfices probed with wire and verified clean. Carb cleaner and compressed air flushed through entire carb. Low speed and high speed jets are perfectly clear.
2. Verified that the timer base is NOT sticking
3. Replaced all fuel lines within the engine (from fuel pump to carb distribution). Checked screen on fuel pump to verify it is clear.
4. Had a friend operate the boat while I pumped the primer bulb. No change.
5. New plugs, gapped properly
6. Removed head, new head gasket
7. Verified all reed valves are functioning properly
8. Replaced intake manifold gasket
9. Verified all throttle plates open and close together
10. Executed lync'n'synch making sure the throttle plates do not open before the timer base advances
11. Verified the plastic sleeve on the carb linkage is 3/8" in diameter and in place
I have not rebuilt / replaced the fuel pump, but I find it hard to believe it is bad since the engine runs well at WOT. Could the pump be bad??
I am really stumped at this point and am hoping one of you sees something I missed. Thanks in advance!!
