1984 Mercury 115 EL

[bluecollerboater]

1984 mercury 115 EL inline 6. I was out running WOT for about five minutes then Boat started coughing and dropped to 3500 RPM. I checked compression 125 to 130 in all six cylinders. Checked spark have spark on all six( used inline spark tester with light bulb). Changed fuel water separator, it had a little water in it not much.

Checked timing was 3 degrees at idle and 19 degrees at wot, specs say 6 degrees at idle and 21 degrees at wot. With today's fuels I am happy with that. Will go to 5500 in neutral. Can only get 3500 rpm under load. Checked the screen inside fuel pump and it looked brand new.

 

[Texasmark]

If fuel supply problems, squeezing the primer bulb would restore rpms. Then where.
If constant 3500 how long and has anything changed in parts-equipment-setup, new boat, has rpms ever been up to 5k+ while on plane?

 

[racerone]

Do not wind it up to 5500 RPM in neutral....Bad for the motor.-------Does spark jump a gap of 3/8" on all leads , yes or no.-----Make sure the 3 carburetors are clean.-----Do not run the motor until you confirm carburetors are clean.

 

[jimmbo]

Is there fuel dribbling out the Bowl Vent(s)? My 84 115 had a tendency for the floats to jam cockeyed in the fuel bowls.and would yield about the same rpms as you are seeing
You mentioned an idle timing of 3*, but a spec of 6*. There is no idle timing spec for these engines, as the retarding of the spark is what controls the low, including idle speeds. The 6* spec is the Pickup Timing Spec.
And still another 'DO NOT REV THE ENGINE above 1500 in Neutral', unless you really want a different motor

 

[bluecollerboater]

I believe it is the high speed winding in my stator. Yes I have achieved a top wot of 5400. I was actually doing around 5200 and all of a sudden the rpm’s dropped to 3500 with sputtering and hesitation. I went back to the dock. In the morning I changed my fuel water separator and went for a spin. Same issue. My carbs have always leaked a little. I seafoam deep creeped all 3 after that she did idle better.

 

[bluecollerboater]

Not sure if spark will jump a gap. I do not have a spark gap tester.

 

[bluecollerboater]

My engine still has the timing sticker on it. It states 6 degrees either idle or static ( I do not remember wording) and max of 21 degrees. I am not home to confirm wording.

 

[Texasmark]

Not sure if spark will jump a gap. I do not have a spark gap tester.

You have 6 installed in the engine. Pull the plug, place case on shiny metal of the engine block, cap installed, and roll it over. Doing this at night helps you to see.

 

[jimmbo]

You have 6 installed in the engine. Pull the plug, place case on shiny metal of the engine block, cap installed, and roll it over. Doing this at night helps you to see.

Spark Plugs are not a good tester for spark, a gap of 3/8" of an inch is needed to verify that the ignition system is up to snuff. A weak spark is all that is needed to jump the plug gap in open air. Add some heat and compression and the Voltage requirement skyrockets

 

[jimmbo]

My carbs have always leaked a little. /QUOTE]

Where are they leaking from, and when? They will spill fuel when the engine is tilted up. If there is fuel dripping out the carb throat when stopped and the engine is in the running position, or there is fuel dribbling out of the bowl vent, then you may have a inlet valve not closing, a misadjusted float, or a stuck float. One carb affects 2 cylinders and that is 1/3 of the engines power. Loss of them will really kill the rpms as only 4 are making power, and have to drag 2 weak ones along