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88 50hp mariner won't rap out dogging down

T

Tnmoutdoors

Member
Serial # 0B308011
Used my boat quitE a bit in the spring and it ran fine no problems let it set for a month and took it out today started right up then let it warm up and headed down the lake and whrn you throttle it it built rpm then it boggs down and it also has a miss in it like it's starving for fuel or something. Changes the bubble on the fuel hose and new spark plugs and still doing it. Any suggestions on where to go next or what the problem may be? I just find it odd that it ran fine the last time it was on the lake and not today
 
Sounds like gummed up carbs from fuel sitting around to long. Try a fuel additive cleaner first on a known clean portable tank. Also check all fuel lines for air leaks,cracks,loose connections ETC. When all else fails, Troubleshoot the following,compression test,spark test, fuel diagnostics!! Pull plugs for inspection,are they light tan,good sign. Are they wet,possible bad spark,Are they sooty black,running very rich fuel mixture.
 
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The top 2 were black and soot on them and the bottom one was tan but it was a little wet. Already did spark test and all 3 plugs and wires were all good
 
Ok I've figure out what is going on but don't know how to figure out what is causing it. At half throttle it is running fine and at full throttle it's bogging down and I have figured out that I am loosing spark to cylingers 1 and 2 with that in miND I installed a new trigger cdi and rectifier just last winter I have ruled out fuel all together
 
My 40 mariner just did the same thing- runs great at idle up to 1/2 throttle. It ran great through 2 tanks of fuel then started acting up-as if a rev limiter was kicking out cylinders. I received a post to check fuel system and voila'- fuel pump and carbs had lots of really fine rust/sand particles in them. This was a 3 hr job to remove and clean everything (I am not a mechanic) but it is not all that difficult to do- just be very careful with small parts.(jets, float parts etc..) Good luck
 
Whats the compression on cylinders? Are you getting a lightning blue snapping spark on each plug while cranking between 200-300 rpms with all plugs removed? we need answers to solve your questions?
 
Compression 115 on all 3
Clean fuel
New bubble
New hosE from connection to fuel pump
Changed fuel filter
Took fuel pump apart and made sure it was clean
Cleaned carbs
Sprayed carb cleaner over whole motor not ducking air
HAve good blue spark at idle
Bump key and starts right up and idles perfect
Half throttle runs fine past half it bogs down like it has a Rev limiter
Did the 7/16 spark test and have a good bluE spark
 
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