Had a derby today and and my engine developed a miss at idle and took forever to get on plane. Once on plane the miss was less noticeable but would only reach 5000 rpm. I'm going to change the plugs out and see if that heals it. Motor only has 74hrs and been flawless until today. Anything else I should check? Serial number is in my signature. And I have no alarms or beeps.
2020 Caymas CX21 Pro
Mercury 250 Pro XS
Serial# 2B686100
Lowrance Ghost
Lowrance HDS Lives
plugs coil wiring to coil all maybes
2022 z519 cup 225 merc 4s ser # 3B210484. 2--hds12 live units. 2 poles, atlas plate, ghost, hamby's, active target, merc digital gauges
2002 basscat pantera 3 (dad bought new) sold 8-2-22
2000 stratos 20 ss (bought new) 200 hp Rude ficht great boat/motor sold 11-21
pulled by a 2500HD Denali
proud dad of an ARMY Captain
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Plug wires and Spark Plugs are the two most likely areas. Don't forget to test the plug wires (resistance test) and compare to Service Manual spec/ranges.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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Thanks Don, I changed the plugs last night and I believe #5 was the culprit. It was way darker than the others. Won’t know for sure until this weekend. I will update.
2020 Caymas CX21 Pro
Mercury 250 Pro XS
Serial# 2B686100
Lowrance Ghost
Lowrance HDS Lives
New plugs fixed it !
2020 Caymas CX21 Pro
Mercury 250 Pro XS
Serial# 2B686100
Lowrance Ghost
Lowrance HDS Lives
I changed my plugs last week [225 ProXS 4 stroke] with only 44 hours on the engine, and it definitely idles better now. After reading several threads in this forum about spark plug maintenance on these V8 engines, I decided that my very high percentage of low-speed/idle running probably hastened fouling of those plugs. Even though I run only ethanol-free gas plus Stabil in my engine, it doesn’t get run hard enough, frequently enough to keep carbon buildup at bay. $68 for a set of plugs plus a half-hour of swearing because the boots were so difficult to pull off is well worth it for reducing internal buildup in the engine and enhancing performance.
Lot cheaper than a opti. Lol
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