Motor Miss Firing

[mean24]

I have a 2004 Suzuki 4 stroke 60hp. it seems to run fine when in idle and lower rpm. but when I rev it up it starts to sound like its skipping and shakes? Is this due to spark plug not firing or a few? Because I tried to change them out a couple months ago with some ngk's.
Thanks guys for your help!

[wevans]

My first thought is fuel pump. Is it a fuel injected system? If so, the fuel pump, fuel filter or the computer is the most likely cause. I believe that the pump may have a resistor on the ground that can go bad, but aint real sure on that one

[Steve Stinson]

I know a couple quick checks that work on older 2 strokes - They may help you, but I've not owned a 4 stroke :

Get a six gallon portable tank and hook it directly to your motor - bypassing all of your existing fuel lines, water separator, etc. If you still have the same problem look at your electrical system / spark.

If you can keep the motor running while the missfire is happening - get some GOOD rubber handled pliers and remove one plug wire at a time. If you remove one and the sound of the motor does not change, you have found the cylinder that is not firing.

The older Mercs did not like Champion spark plugs, but ran like crazy on NGK's. If you changed the brand of your spark plugs I would go back to the brand that was in there when it ran correctly.

Hope this helps.
Steve Stinson
President
NFGFC

[dombern34]

has it been sitting up all winter?

[Jumptrout51]

You will find your problem in the high speed fuel jets.

[FUTCHCAIRO]

GET YA SELF SOME CHEMTOOL AT WALLY MART OR CAR PARTS HOUSE, CRANK UP ENGINE SQUIRT JUST A SMALL AMOUNT INTO THE CARB.. BE SURE ENGINE IS HITCHED UP TO WATER OR IN WATER, THIS CHEMTOOL WILL CLEAN OUT MOST THINGS IN THE JET, ONLY PROBLEM IS WHEN YOU SQUIRT IT IN THE CARB IT WILL CONTINUE TO RUN EVEN WITH THE IGNITION SHUT OFF, THIS BEING THE REASON FOR HAVING THE ENGINE HITCH TO WATER. HOPE THIS HELPS.
PA
SEMPER FI

[Mister Mullet]

Rubber pliers? We don't need no stinkin' rubber pliers. Be a man.

[mean24]

Lol mullet I'll let you man up any day you want and start pulling plugs without rubber. Ha ha
But it actually is a fuel injected motor, I'm sorry for not specifying that. Yes it's been running and not sitting up. I just didn't know if the spark plugs were not spaced right?!? I mean I thought majority of the time ngk's come pre spaced

[fishinfool]

You gap is probably .035" to .040". I am using this from experience with other fuel injected engines. You are correct that NGK pre gaps their plugs but only if you order per part number for a specific application, ie... 2004 Suzuki DF60 etc... Probably a fuel issue. Ethanol wreaks havoc on outboards, from the tank to the fuel lines to the engine components.. It could be a piece of rubber that has broken down and started crumbling thereby partially blocking an injector or something similar.
Good luck