Opinions on how my spark plugs look?

[Tomtina3]

Hey everyone, I have a 1978 Evinrude 70 hp that doesn't seem to have the thrust it should at WOT. I pulled the plugs last night, and need some opinions from people who have looked at lots of spark plugs - Pics attached below. The plug tips on all 3 cylinders looked different which concerns me obviously. Cyl 1 (top) looked brown and well-burned. Cyl 2 looked black and a little oily. Cyl 3 looked very very clean, even more so than the picture seems to show. Can I get opinions please? Thank you!!! PS- Looks lik ethe pic download reversed the picture order. 1st pic is Cyl 2, then Cyl 3, then Cyl 1.

 

[racerone]

Post the results of a compression test.

 

[Tim Frank]

+1 ^

 

[Tomtina3]

Cyl 3 (bottom one) is a little low but not terrible. Cyl 1 - 120, Cyl 2 -116, Cyl 3 - 100.

 

[Scott Danforth]

cylinder 3 is more than 10% down.

 

[racerone]

I would remove the cylinder head to do an inspection.

 

[Bosunsmate]

whats the piston head look like on three, look through the spark plug hole

 

[SparkieBoat]

you could also try a decarb. and make sure that bottom carb is clean and the float is set right

 

[Tomtina3]

Thanks everyone for all your help and suggestions! Although, no one has answered my original question, which is... by looking at the burn patterns on the spark plugs, can anyone give me more information about how they would interpret the conditions of the plug tips?

 

[racerone]

??????----Based on the looks of your sparkplugs you should do a compression test.-------You did that and have you now removed the cylinder head for an inspection of the cylinders ???