Hello,

I got this new motor (new to me) and it's a 25hp merc 2 stroke. i pulled the plugs and the electrodes are in great shape but i noticed the plugs were a little darker than was a car's plugs would be.  i assumed this was because it has gas/oil mixture.  they weren't black by any means, i'd day a dark gray.  does this sound normal?

thanks

steve

Should be a nice tan. Black means its running rich and white would mean its running lean, which is very dangerous.

Should be a nice tan. Black means its running rich and white would mean its running lean, which is very dangerous.

X2

Go a little heavier on the oil. Plugs are cheap. A burnt up powerhead is not.

If the motor has idled before looking at the plugs, you're wasting your time.  To get an accurate reading you need to run the motor at WOT for a few minutes (on the lake of course) and then cut the switch off or pull the emergency kill while still holding motor wide open.  Then pull the plugs and look at them.  As mentioned, on a carburated or normal fuel injected motor they are going to be about the color of a brown paper bag, maybe just a touch lighter.  On DFI motors they will be a lot lighter because being computer controlled, the fuel mixture is much more precise.  All motors are going to darken the plugs when idled.

Acutally going heavier on the oil does nothing for lean or rich, it can actually add to helping a lean motor melt a piston because the extra oil tends to make the piston hold more heat and melt quicker.  Plus it greatly adds to the carbon buildup in the motor.

gotcha, thanks. that makes since about inaccurate readings at idle.

The plug in your 2-stroke will look darker than the plugs your 4-stroke car; 2-strokes burn oil in the gas which will give a darker appetence. Heavier oil will do any good but a higher oil to gas ratio will.

Run it a WOT like way2slow mentioned and check the way he stated  

Catt, ya'll have come up with some wrong info somewhere, adding more oil, heavier oil, anykind of extra oil will do nothing toward making a motor run any richer if it's lean.   More oil will only add to the problem and cause increased carbon buildup.  More oil will make the piston hold more heat and heat is what causes one to melt.

Excuse me ole master  

On a 2-stroke carburetor you have an AIR mixture screw; on a 4-stroke carburetor you have a FUEL mixture screw.

If you have a 4-stroke, turning the screw OUT (CCW) makes it richer (more fuel)

If you have a 2-stroke, turning the screw OUT (CCW) makes it leaner (more air)

Well, again not quit right.  First the  mixture screw on most all modern day motors is for idle only, has nothing to do with midrange or WOT mixture, which is where you melt pistons

The direction you turn the screw has nothing to do with the type motor, stickly the type carburator.  If it's an air bleed carburator, meaning the screw is controlling the vacuum, then as you turn the screw out CCW it makes the idle learner.  If it's a fuel control carburator turning the screw out CCW makes the carburator idle richer.

For instance, 92 - 95 200 hp Johnson ran Air bleed carbs with idle adjustment screws  and CCW made them idel leaner, 96 and later ran fuel adjusted idle adjustments screws and CCW made them idle richer.   Again though, made no difference with anything other than idle mixture, they would still melt a piston in a heartbeat if you have the wrong main jets in one, I've got at least a dozen pistons that will prove that point.

Running some oil mix with the gas will protect you from oil pump failure. As Catt said a little oil is cheap.

Garnet

It's ya'lls motors, you can run as much of any kind of oil you want, just what ever makes you fell comfortabel.

In my motors, the only time I increase from 50:1 ratio is on my hotrod motors I'm turning over 6,500 rpm.  

On my stock, oil injected motor, I do not and will not add any addtional oil to the gas, this only causes more carbon build up.  Even if you mixed it as heavy as 100:1 in the tank, that would only help save the motor at very low rpm, if running WOT and the oil pump quit, it would still most likely take out the crank/pistons before you got the motor shut down.

On a DFI motor, it would make no since because the gas and oil doesn not even go through the crankcase.

Anyway, like I said, no one can tell anyone how to run their own equiment, I just know how I would run mine and that's all that matters to me.  We've Done beat this dead horse too long already.