Do I need to go to a mechanic?

[muttmechanic]

I have a 2009 15 hp 2-stroke yamaha. I ran it today on some rabbit ears in the drive way and I would rev it up prolly 1/3 of what it could do and it would backfire about every other time. Is this something I need to have someone check out or is that something common for engines like this. This is my first boat motor I've ever owned so please pardon my ignorance toward the subject. Thanks for any help you can offer

[jchief]

should not backfire. try changing spark plugs first

[CrazyD]

Is the fuel old? Are you sure your gas/oil mix is right?

[Dink]

Capt obvious says....

[speck-chaser]

check da fuel!!!

[muttmechanic]

the fuel is mixed right. I got these bottles that put exactly enough in for my 6 gallon tank. The gas may be 2-3 months old but I put stabil ethanol treatment in it so it should last longer than normal. It also shouldn't be water if that can potentially be it because it has a separator on it

[muttmechanic]

If fuel is what ya'll are thinkin maybe some of the older gas didnt mix and now that's what's causing it. That sounds like something easy to try at the very least

[speck-chaser]

how old is the separator?

[muttmechanic]

everything with the motor was purchased in like january 2010 if I remember right, but regardless in that ball park

[flounder_smacker]

change the plugs. bad fuel wont make a engine backfire but make it stutter and miss. also revving in neutral will cause backfiring in carb motors cause you are giving it more fuel than what it can burn and the fuel is igniting in the exhaust instead of the cylinder. put the boat in water and see if it acts the same.

[huntin fool]

Go back it off at ramp. Like flounder said, revving will have some backfire. Mine does it when cold...

[Gerald]

Another possible cause is that a spark plug wire is loose.....ie. not tightly connected to the spark plug.

To check....grab the spark plug wire [not while the engine is running] and see if you can easly turn the rubber part that covers the end of the spark plug. If it feels tight......then try pushing the rubber end onto the spark plug.

After checking the spark plug wires......like others said, go run the outboard engine in water under load to see if it backfires. If it still backfires [or even if it doesen't backfire] pull and clean or replace the spark plugs.

Depending on how much you use the boat..... spark plugs should be changed ever year or two.