BUHW spark plugs fouling in a 1986 Mercury 115 hp in- line 6

[HarryDeWhit]

Is there a Non-foul Spark plug to replace the NGK BUHW spark plugs that will fit in a mercury 1115726 in-line 6 cylinder outboard? On cold start condition, the BUHW plugs foul constantly.

 

[Dukedog]

if its fowlin' buhw's its got a problem somewhere with cold idle circuit....

 

[Chris1956]

Agreed.....BUHWs are not my favorite spark plug, but they do not foul unless something is wrong. Are you getting water in the cylinders? Is the fuel pump leaking fuel into the cylinders?

 

[HarryDeWhit]

Chris, no water getting into the cylinders and the fuel line routing carries the fuel out of the bottom of the fuel pump, loops up into the bottom of the filter, out of the top of the filter then up into the carb. input tiubing. When I try to cold start, there's no ignition unless I apply the electric choke intermittently. After a couple of almost (false) starts, the plugs no longer fire, and when I pull them, they're fuel fouled. I'm thinking the plugs aren't firing hot enough for the cold start. Alao would you know if the Champion 827M spark plugs are any better?

 

[jimmbo]

I never had any problems with the NGKs that came from the factory in my 84 115, it still had those same plugs in it 14 yrs later when I traded it in. Now the FICHT I traded it for went through several sets of Chumpion plugs every season

 

[HarryDeWhit]

Thanks Jimmbo. I'll forget the Champions

 

[jimmbo]

Are you mixing the Oil and gas thoroughly? I don't remember when the God Awful autoblend was introduced. Just dumping the oil into the gas will result too much oil at first, then almost no oil as the tank runs low.

 

[HarryDeWhit]

Jimmbo, I learned a while back that it's best to premix the oil and gas in a separate container then pour it into the tank. Also, before it comes up, I've already rebuilt all three carbs, complete with new floats.

 

[jimmbo]

Jimmbo, I learned a while back that it's best to premix the oil and gas in a separate container then pour it into the tank. Also, before it comes up, I've already rebuilt all three carbs, complete with new floats.

Nice to see someone taking the time to actually mix their fuel properly. All too often, over the past 45 yrs. I've seen people carefully measure out the correct amount of oil, fill the tank with gas, pour the oil in, put the cap on the tank, start the engine and drive away

Since you mentioned it, are the floats set correctly, inlet valves closing? Idle mix not set too rich? Mixing the oil-gas at 50:1, and not cheaping out on the oil(TCW-3)?

Are you getting a good strong spark? The CD ignition systems were supposed to be able to fire the most seriously fouled plugs. At least that's what the Propaganda consistently claimed

 

[HarryDeWhit]

Jimmbo, Had to adjust the new float levers for proper needle and seat closing, and set the idle mixture screws at the recommended 1 1/8 turns out from lightly seated. I am using TCW-3 oil at a 50 to 1 ratio, but I just read Sticky's post on the proper cold start procedure which I'm going to try tomorrow. If it works, I'll have to tear into the remote control unit to try to fix the switch that disengages the shift linkage from the throttle linkage for the cold start. Thanks for your help with this.

 

[Chris1956]

The fuel pumps on most 2 cycle OBs use crankcase pulses to pump fuel to the carbs. The heart of the system is a diaphragm that pulses. If it gets a hole in it, raw fuel is introduced into the crankcase, likely flooding some of the cylinders. You might check yours.