mersury marine 9.8hp 110 1979 plugs fouling

[mercurymarine98]

↵Hi. I have been running my motor in a barrel and after about 16 min the motor starts to buck and I have lack of power, and then the motor eventually quits. When I pull the plugs there is oil coating the electrode. I am using a NGK BUHW-2 spark plug and using a fuel mixture of 50:1 regular gas and a two stroke motor oil. I have installed new spark plug wires. I have been told that I need to open up the throttle and this will burn the oil off, and keep the motor from bucking and losing power. any other suggestions

 

[mlbinseattle]

Can you provide a picture of what one of those plugs actually looks like with the "oil coating"? I'd like to see it before I'd say those were actually fouled. Plugs are usually self-cleaning, that is, they will burn off any carbon deposits or oil provided the rings/block/fuel delivery is in good condition. It's not uncommon to see "wet" plugs after an engine quits since this is usually unburned fuel. Some more info would be helpful, as well. Does the engine quit while just sitting there and idling? Did you check for spark right after the engine quit running? Will the engine rev and remain running when it begins to buck and lose power? Is it easy to restart, or does it need to sit there and cool down before you can start it again?

I use those same plugs in my engine. Right off the top of my head without knowing anything further about your engine, I'd say that the quality of spark may be lagging somewhat and not causing the spark plug to provide a really good spark. After a bit, the spark plug gets overwhelmed with the amount of fuel being dumped on it and is unable to burn all of the fuel. Then again, it may be running way too rich with poses the question: How does it perform under load (in the water with 1/2 to full throttle)? Just my thoughts. Again, more info would be helpful.

 

[Texasmark]

I'd say, get it out on a light boat and run it at WOT for a half hour with about 2 oz. per gallon of fuel/fuel mix (whatever you use) Sea Foam. WM has it. Don't worry about wet plugs on an outboard. That's why Merc invented the 40,000 volt spark......to make stubborn ones with oily film all over them work!

 

[mercurymarine98]

Thanks for your input: I got a couple of response to my Questions and they seem to match up. I will put the motor on my 12 foot aluminium boat and take her for a run and see what comes up. If this works then i am going fishing if not I will post picture and try again.

 

[Texasmark]

Thanks for your input: I got a couple of response to my Questions and they seem to match up. I will put the motor on my 12 foot aluminium boat and take her for a run and see what comes up. If this works then i am going fishing if not I will post picture and try again.

Don't forget the SeaFoam!

 

[60sboater]

Are you using 2-cycle oil for outboards and not the kind for air cooled engines?

 

[Texasmark]

Are you using 2-cycle oil for outboards and not the kind for air cooled engines?

To define it accurately it's TC-W3 aka Two Cycle-Watercraft, 3rd revision. It apparently has different additives because water craft run at a comfortable 150ish or less thanks to thermostats and water cooling, and don't run at full throttle all the time. Your weed eater or chain saw is balls to the wall (at least mine are) while it's running and no water and thermostat to control the temp. So it's the chicken and egg thing. Which way is better if using the wrong oil, if there is a better.

 

[mercurymarine98]

Hi all I did put my motor on my boat and ran it on a lake with a 60:1 fuel(premium/ Castrol outboard motor oil. The motor seemed to run well in idle and trolling speed, When I went to trottle up in fwd I could not get the motor to hit the power band. When I shifted into Rev. the motor hit the power band with no problem. In Neutral I could rev the engine and hold power by moving the trottle arm on the carb. I tried this in fwd but could not hit power band. Is there something in the linkage that would create this kind of problem.

 

[Texasmark]

Bigger engines vary the timing as a function of rpm so I guess your size does too. For my last Merc 90, the number was around 4 BTDC at idle to 22 at WOT. Does make a difference in performance. Can't judge idle nor reverse for that matter. Not much load on the engine so you don't need that big of a bang in the cylinders to get the power you need. At higher rpms you need to lead the bang more since the piston gets there faster and the bang time from ignition to explosion is pretty constant. If you don't get it out there early enough the piston will be part way down the cylinder before the explosion fires and you can't push much with that.

 

[mercurymarine98]

Hi All: changed mixture fuel/oil 60:1 and my spark plugs came out like the attachment. If I pulled the plug and cleaned them the motor would start easy and run for about a minute before it started to miss and lose power. has anybody ran 100:1 in a merc 9.8hp 110 to stop this plug fowling or should I be looking else where say at my coils, ignition module or magnets on fly wheel? Can these module be tested?