merc 2.5 piston wash pics, rich or lean??

[superboattwin250]

we pulled the heads on my cousins motor over the weekend just to check everything out.I thought the piston tops look lean. there is almost no wash. what do you guys think?

[Eagle One]

Could be a tad lean but running on a cool dry day will usually show up leaner than the same setting on a regular average humidity day. You can see the carbon pitting around the outside of the pistons a bit but heat will also cause that. Then again the color is not as light as a lean condition would show but idling after running will darken the tops. I'd suggest reading the plugs after a power run. Use a set of gap type plugs. Call me if you need more info. Glad to help

[NH LTV]

What NGK gap plug would you recommend? Also, what should the gap be set at?
Thanks

[bigbluechevy454]

br9hs 10

[superboattwin250]

I do run the br9hs plugs as well. im thinking it is a bit lean. usually when I pull the heads on these outboards there is more wash from the fuel leaving some clean spots on the piston next to the transfer ports

[merc326]

Looks a bit lean to me also, tops look a little dry. As already said, it really depends on how long the motor idled before pulling the heads.

[superboattwin250]

Probably was idled for about 2 minutes through the no wake zone before he killed it at the dock. Then we pulled the heads at my place

[Mr. Demeanor]

Looks really lean to me. I see no wash???



My pistons and this was a little rich but safe. I am a little leaner than this now. Plenty of idle time and a flush before that head was pulled.

[Mr. Demeanor]

PS. reading the plugs especially if your running E10 fuel is not reliable at all. Piston wash is a much better method. Just do a little research on 2 stroke piston wash vs plus reading.
Its so accurate that I have 3 different sized jets in my 4 carbs to get an even wash on all 4 pistons. The plugs wont show you that accuracy.

[Mr. Demeanor]

Just found this pic looking through my folder.
Stock motor piston wash. This is a domed piston so the wash will be a little bigger but you should clearly see some bare aluminum.

[superboattwin250]

Yeah thanks for the pics. We are not seeing any clean aluminum on the piston near the Intake ports, that's what made us think it was lean. Thanks again guys. Guess we will have to richen it up a little