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Mercury 25xd Trouble

J

jamie_h

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"I have a 1985 25xd that won&#

"I have a 1985 25xd that won't run top end. When I bought this last year it ran great, top end long distance no problem. End of season it started to cut out at top end so i had a pro work on it. He changed the trigger/s, cleaned up the carb - took it out a couple times no problems. 3rd time out after repair it started again. He had told me that if it happened again that it would most likely be the switchbox. So at this point I have changed the switchbox and coils and wires. Took it out tonight - It starts within a second of turning the key every time, idle's fine and runs good up to about 75% (18-20mph) push it all the way and it acts as if it were choking out, bring back down to 75% and its fine. Pulled the plugs - not fouled. What the hell is wrong with it? Any ideas would be greatly appreciated."
 
"pump the fuel bulb to see if

"pump the fuel bulb to see if it helps to determin if its a fuel problem. Danger, running with lack of fuel means lack of oil. Put a timing light on each plug wire, when it misses look for a miss in the strobe light, look for the bad cyl. 2 people for this test on the water. I'm guessing fuel supply."
 
"took back out today - ran goo

"took back out today - ran good first 15 min about 90% (22mph), shut down and when restarted would only run staedy at 6.5 mph, any more and kaput. pumping the bulb chokes out the motor. Back home pulled the plugs, wet and black. ???"
 
"Pulled the carb - Clean as a

"Pulled the carb - Clean as a whistle. no gunk in tank or fuel lines. Will check compression tomorrow, will bad rings foul plugs? And will a Bad cylinder fail only at top end?"
 
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