Outboard misfiring

[bermagui aust]

Hi. I am a new member with a problem with a 2000 model Yamaha Salterwater series 130 hp o/board.
They are on a sharkcat but only one is a issue.
Running at idle it goes for 1 or 2 minutes then sends out a chuffing noise, looses revs and stops.We have changed the sparkplugs put in new fuel, cleaned the carbie intake silincer. The carbie intake silencer had about 1/4 inch of oil in the bottom and top box. Cleaned out the oil tank on the motor, which appears to have overfilled itself, and excess oil had gone into the airbox of the carbies. But every coouple of minutes still the cuffing noise and a distinctive miss. We have readjusted the oil injection pump as with the thrttle closed the arem was not against the stop as per the instruction manual. On checking the spark plugs one was black and sooty and the remaining three were between moist and wet. Do the oil injected motors require higher octane. We run unleaded which is about 91%octane. Is this sufficient for correct mixing of fuel and oil. Could it just need a good run outside now that I have done all the above things or can anyone suggest something that we may have overlooked. As the second motor is running puurfect we have tried to cut down on costs by swapping parts over to see if there is any difference. I sure hope someone can help me out. I am just a housewife who eats breathes fishing, and if we cannot solve the prob, it might be more than just the outboard I trade in.

[Ken]

Aussie,
I just checked the owner's manual for my 2000 C115, and it shows 86 minimum octane for both the 115 and 130 - anything more, and you are just wasting money. Most owners here run 87 octane, which is the minimum available - for both pre-mix and oil-injected.
On the motor that misses at idle, I would do a shock treatment with SeaFoam or RingFree - this will de-carbonize the motor (really should do both) and clean up the fuel system and carbs somewhat. Sounds like low speed or idle jets may be clogged with gum/varnish.
If the shock treatment does not help, then a carb overhaul may be in order.
Also, your fuel pump may be getting weak. Some owner's replace fuel pumps every five years, on average, just as a preventive measure.
If the spark plugs are more than a year old, replace them.
Good luck [img]smile.gif[/img] ,
Ken K

[bermagui aust]

Many thanks for that info.

[Wally]

That sounds like what my 90TLR was doing. It would run great but at idle would miss every few seconds until it stalled.

I had to take the carbs off and do a complete cleaning with NAPA carb cleaner and install new carb kits. That solved the problem for me.

[Bluebird]

Try some Berrymen's Chemtool spray in the low speed jet hole. Last resort before you have to pull them off and clean them out. Bottom the jet screws out (soft stop) counting how many turns it took. Then unscrew them completly, spray the in the chemtool then replace the jet screws turning them out the same # of turns as before. Good Luck!

[troppojohn]

I think the chuffing is ignition in the exhaust system, could be caused by incorrect timing, I have a 60hp and had the same problem, I found the timing well out and after adjustment the problem has disapeared Try everything!