240 sport jet

[Merc 2.5]

You changed spark plugs and milky oil disappeared? And you picked up RPM? Were the spark plugs loose and you sucked in water every time you came off plane? LOL Just kidding. You must have had a misfiring cylinder. Probably ran on all 6 at low RPM but misfired at high RPM so you can barely notice it. The unburnt fuel/oil caused the milkyness. You fixed the misfire so the milkyness is gone. Got a spark plug tester? They are really cheap.

100-240V Dual Hole Automotive Spark Plug Tester Diagnostic Ignition Test Device | eBay

I would had noticed a cyl dropping if it was a misfire, I have a good ear for that kinda stuff , 90% of the time I can hear if a motor is in "tune" or not. I guess it's possible I had a carb barrel leaking in a cyl but carbs r dry with no fuel running out front , when trimmed up or anything. Needles ,seats,floats r good. So idk. But I didn't mess with carbs either. No water intrusion because I been watching closely for that , it was my 1st thought awhile back

[skialot2]

Well, you changed your spark plugs and picked up RPM. I would have to say something wasn't firing right. Not a dead cylinder. Just a misfire.

[Merc 2.5]

Well, you changed your spark plugs and picked up RPM. I would have to say something wasn't firing right. Not a dead cylinder. Just a misfire.

Ya. It wasn't sounding as crisp at idle either until I changed em , now back to normal. Ya it turned a 28 to 6700 quick and was still climbing and pulling hard , I also ran it for few yesterday and double checked everything and milky crap is gone , I guess it's the 1st spark plug issue I've had in many many yrs on one these things. Idk if I got some bad plugs or ngk quality goin down , but I believe been doin that since I bought em

[25two.stroke]

NGK quality going down. So is champion.

FYI mercury has changed which way the lower crank seal lips face throughout the years...just glance at a few different manuals.

[LakeFever]

Plugs are not lasting as long for me either. Definitely some qc issues. I bought a cheap spark plug tester that goes to 9000rpm as well as some of the light testers that go inline with the plug and wire on the motor to verify for spark. The electrics on the motor so far have always passed but the spark plugs tend to go weak. I’ve not had one complete dud yet but definitely weaker spark on some than others. I recently switched back to the gapless to try those again.

[Onetime]

Tuff to tell the difference but there is some cheap NGK clone spark plugs out there that are crap.
Buy from a reputable retailer.