2001 Mercury 115HP Salt Water series - difficulty sustaining idle - fouling spark plu

[twr7cx]

My 2001 Mercury 115HP Salt Water Series (2 stroke 4 cylinder carby self mixing oil outboard) has recently been serviced and carbs tuned - it starts very easily and runs as well as ever. It idles reasonably well too (it's the model that drops to 2 cylinders for idle so sounds a bit rough as to be expected) - for a while at least. After idling for a bit (a few minutes) it will eventually stall, when this happens it will become difficult to start and not want to idle again.

I suspect that the cause is the spark plugs are fouling. The average water temperature here is only 14.36*C (approximately 58*F) - so pretty cold. I am running the standard spark plugs (NGK BPZ8H-N-10). I'm wondering if a hotter spark plug (such as 7 or 6 range) may help to prevent the fouling of the plugs at idle?

 

[dingbat]

What oil are you using?
I troll in water temps a lot cooler than that. That the lower temps my motor doesn't like some oils. Experimented with many and found semi-synthetic oils helped a lot. I run evinrude XD-50 but any semi helps the situation

 

[Texasmark]

What oil are you using?
I troll in water temps a lot cooler than that. That the lower temps my motor doesn't like some oils. Experimented with many and found semi-synthetic oils helped a lot. I run evinrude XD-50 but any semi helps the situation

Walmart down here sells Pennzoil Semi TC-W3 in the sporting goods section here. That was my preference and a lot better price than the OEM oil sitting next to it. Also get some Sea Foam (WW has that too in the auto section) and add to the gas; directions on label. I learned about it on here and it helped me over the years. I went 10 years on a seldom used '02 90 triple with no varnish buildup in he carbs. Don't know how long that would have lasted but when I checked them they were clean.

Nothing wrong with the OEM surface gap plugs. Leave them be. Just because they come out wet and have spark tracking across the insulator doesn't mean anything is wrong with them. I had a set in a tower of power 115 for 9 years and they were still hanging in there.

Mark

 

[racerone]

The motor only idles on # 1 and #2 cylinders.----A compression test is a good idea here.-----A cylinder that is running cold due to internal problems will not keep the plug clean.

 

[twr7cx]

I have been using the Castrol Outboard 2T oil < http://www.castrol.com/en_au/australia/products/other-products/boating/outboard-2t.html > lately.

I will conduct a compression test tomorrow on all four cylinders.

 

[twr7cx]

I finally got around to running the compression test today. From the top cylinder to the bottom, these are the results:
120 psi
118 psi
121 psi
114 psi

Which is number 1 cylinder? The top or bottom?



I also took a picture of each spark plug after removing incase someone on here knows how to 'read' them?

 

[jerryjerry05]

No Title

Top is #1
Plugs look good. How old?
What's the idle RPM'S set at?
The heat range of the plugs should be ok.
Check the spark and see if all 4 are bright blue and jump 7/16"

 

[Silvertip]

If that engine is supposed to have surface gap plugs -- these definitely are not. Also check the plug gap if these are the right plugs. The gap looks awful wide but then the picture may be skewing that a little.

 

[twr7cx]

If that engine is supposed to have surface gap plugs -- these definitely are not. Also check the plug gap if these are the right plugs. The gap looks awful wide but then the picture may be skewing that a little.

NGK lists the BPZ8HN-10 spark plugs for it.

I do not know what the correct gap setting is though.

The motors details are:

 

[twr7cx]

Anyone know what RPM these motors should idle at? I increased the idle speed today and had no stalling issues.

 

[Texasmark]

If that engine is supposed to have surface gap plugs -- these definitely are not. Also check the plug gap if these are the right plugs. The gap looks awful wide but then the picture may be skewing that a little.

The manual lists surface gap or an alternate conventional plug. No longer have my manual so can't quote numbers. I have run both in my engine, a triple 90 kid brother and SGs run better for me. However for the 100, 115, and 125 engines, I vaguely recollect that they do recommend the conventional as the basic OEM preference. Apparently it has to do with the way the 2+2 works the fuel without igniting it at low speeds.

Mark

 

[dingbat]

Walmart down here sells Pennzoil Semi TC-W3 in the sporting goods section here. That was my preference and a lot better price than the OEM oil sitting next to it. Also get some Sea Foam (WW has that too in the auto section) and add to the gas; directions on label. I learned about it on here and it helped me over the years.
Mark

I get one gallon case lots of XD50 delivered to the house for $21.60 a gallon. No need for additives. XD50 has carbon guard in it's formulation.

Pennzoil Semi is $17 a gallon here. Add the cost of Seafoam and the time and fuel to pick it up, XD50 becomes a cost effective alternative.

I can get Yamalube at $18 a gallon in my container, but driving 60 miles round trip to pick it up isn't cost effective.

 

[dazk14]

I get one gallon case lots of XD50 delivered to the house for $21.60 a gallon. No need for additives. XD50 has carbon guard in it's formulation.

Pennzoil Semi is $17 a gallon here. Add the cost of Seafoam and the time and fuel to pick it up, XD50 becomes a cost effective alternative.

I can get Yamalube at $18 a gallon in my container, but driving 60 miles round trip to pick it up isn't cost effective.

Here we go...and oil debate.LOL

However, +1 with dingbat's point of view, the carbon guard being the biggie!

 

[racerone]

The one sparkplug has a white ceramic compared to the rest.--------Needs to be looked into.

 

[Texasmark]

The one sparkplug has a white ceramic compared to the rest.--------Needs to be looked into.

Nice catch on that little piece of evidence. Since the insulator is not tan like the others one would expect this cylinder is loafing. 4 carbs on this engine as I recall, 1 per cylinder so could be the carb lean/clogged, or the CDI could be loafing. Doesn't seem clean enough to be water intrusion and Merc is pretty goon on corrosion protection anyway and no head gasket to leak.

My 2c,
Mark