yamaha 2002 f225 misfire

c stuard · 09-17-2009, 06:06 PM

re posting here as i didn't get much help on the general forum...
last summer engine started w/ a cold running slight misfire when trying t9o get up on plane. so we just idled a little longer each run before getting up on plane.this summer got to be more problematic.As i open the throttle the engine misfires a little at maybe 1800 rpms so i back out maybe 200-300 rpms,run there a minute,add more throttle til it misses,back off a little.takes maybe 4-5 steps til I can get on plane at 4000 rpm.Once up and running it's fine for the rest of the trip.When it was real bad a month ago, it would miss at cold idle so i pulled one plug wire at a time to try to isolate it to one cylinder.Each wire made the engine run much worse so it's not just a one cylinder problem.Also could hear what sounded like engine popping back in the intake which makes me think it's lean.replaced plugs and ran the engine on injector cleaner we use at the dealer where i work as a master car tech.had the tank pickup out to check and replaced the squeaze bulb and all the rubber hose from tank to the filter on the engine.replaced that filter too.it's now back to it's initial situation where it cold idles ok and we need to take it easy for the first mile or so before getting on plane but only one or two steps needed.We run on gas station gas same as our cars but are in Md where there is a max 10% alcohol.your thoughts on what to check next will be much appreciated

A1 Outboard · 09-21-2009, 04:47 AM

If you have throughly decarboned the engine, you should check the fuel pressure. The fuel pump in the VST has a filter on the bottom which when dirty will restrict fuel delivery. All fuel filters on the engine and hull should be replaced yearly. The ignition system on this engine is the waste spark style. When you disconnect a plug the other plug on that coil will not fire. Todays gasoline causes carbon buildup in outboards that does not occur in cars. You may need to replace your plugs after decarbon. Always use the plugs the manufacturer specifies, do not subsitute.

c stuard · 09-22-2009, 05:54 PM

thankyou for your reply. Don't know the term VST but will search yamaha parts diagrams. A clogged filter would sure fit my problem and i didn't know there was another one besides the one in the water seperator on the fron side of the engine.thanks.will call to tomorrow!

mkalink · 09-27-2009, 11:19 AM

Check out this site should have all the info you need. http://www.bogueinletnc.com/yamaha/

crazy8 · 09-28-2009, 06:42 PM

Dirty injectors. See it all the time. Popping back through the intake is a lean spit/backfire due to too much air not enough fuel. The early F225's had different style injector nozzles that are much finer than the new ones. Prone to clogging much more so than the new ones. This CANNOT be fixed by yourself. The injectors need to be sent out to a reputable fuel injector service center (Flagship, Marren Fuel Injection, etc.). Do not continue to run the engine like this. You are causing detonation by running the engine while lean. F225's dont like a lean condition. You will burn pistons/rings.

Not trying to be a d!ck, but re-read your posts and correct the grammar, very hard to decipher what you are trying to say.

PS- I am a certified Yamaha Master Technician.

c stuard · 10-04-2009, 02:22 PM

Well, had time today to do some checking following info on mkalink's link. Starting outside working in, I got to the low pressure pump first.Had my wife turn the switch and heard it run as it should.Then removed the "F" filter and rigged a test hose into a can. No fuel even though it runs.Squeezed the bulb and this makes fuel come out of the hose. Turned on the ignition again, thinking maybe it had lost prime when I had done my first test, but still no fuel. Pinched off the hose in the line that bypasses the pump and has a one way valve,thinking the valve could be stuck open, but still no fuel.So looks like I need a new pump.Question is why are they approx. $600. I have an inline pump for a car in the garage made to be used w/ a carb (so max 12# pressure) that I paid about $55 for. Looked at Summit Racing, where I buy a lot of stuff for the car, and found a couple of other pumps in the same price range. A price bump by a factor of 10 times is a little rediculous even though it is 'marine' grade.
PS. Sure hope my grammer is ok this time!

A1 Outboard · 10-05-2009, 04:27 AM

Messing with the fuel system without knowing what you are doing will get you into trouble! Marine parts typically cost many times more than generic auto parts. Replacing marine parts with auto parts that look the same can cause catastrophic results. Fires on boats can be deadly. See your dealer to solve fuel system problems.