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Merc 75hp 4 stroke wonbt idle

C

cousinrb

New member
"Hi, I have a 03 Merc. 75hp 4s

"Hi, I have a 03 Merc. 75hp 4stroke. Last year at the first of our season I had the problem of
the engine not idling. I took it to a merc dealer and they checked comp,did leak test and did
all checks with analyzer and prognoses was every thing was OK. Put in new plugs and sent me on
my way.(with a $350 lighter wallet) It run fairly well last year, but there was always a little
carb. spit now and then. This year I started it after winter storage and it started and ran well.
In about 3 weeks I got my dock put in and put the pontoon in and it ran and idled ok. I went back
to the boat in around 2 or 3 weeks and the motor will not idle. It will run at 1500 or so just
fine but will not idle. If you can get it in gear it will run WOT but will not idle. Changed
plugs no help. With engine running I can cover intake to # 1,2,3, carb and engine will rev.
Cover # 4 and nothing.I can unhook all carb linkage and #1,2,3 and 4 carb will rev. engine.
With engine running if you spray carb. cleaner in carb's #4 will not respond??? All have spark."
 
"At least it's a 4 stroke

"At least it's a 4 stroke so you don't have to worry about lack of oil to the cylinders.

Not alot of us here have significant experience with 4 strokes, and in particular any "weird or quirky" problems. They just haven't been around long enough, or been prolific enough yet, so any of us here may not be able to give you better/more/different advice as compared to your local shop.

However, from what you describe (first spit some gas, and now doesn't appear to make any difference if carb 4 is there or not), it kinda sounds like you had an intake valve that was sticking (and the cylinder pressure was blowing the gas back out initially) and now it's totally shot/stuck/broken spring or just plain needs adjusting.

Have the valves ever been adjusted? if not, I may tend to start there."
 
"Did the same last year and de

"Did the same last year and dealer did comp. test, leak test and all was ok. Has good comp.
Ran fine when first started this year. Still runs fine at WOT just won't idle."
 
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