115 Evinrude Starflite Ignition question

[HypnoCraft]

Hi Guys,

My evinrude recently started having a cough or misfire of some sort. at idle and high speeds. idle its a single cough every once and a while and at highspeed it a sputtering and loss/surge in power.

The issue is intermittent.

I pulled the spark plugs and they are all fully black and slightly wet with oil. The spark plugs are less than 4 hrs of run time new. I recently swapped them from NGK to UL77V Champions. That is all that has changed since last season.

Another thing is that there is a residue of gas and oil in the engine compartment. It seems to be coming from the exhaust housing, so a seal job may be in my future.

I am about to start trouble shooting the ignition system, but I read a post that said the ignition trouble shooting is outdated in the manual. how do I go about checking the pulse pack? mine is original, so I am thinking the manual's method will work fine?

Also, if anyone has any ideas on what may be causing this problem, please let me know.

 

[jimmbo]

Model # would be nice to know

 

[HypnoCraft]

Model # would be nice to know

I missed putting down the year or model number. Sorry about that. It's a 1970 model no 115083D.

 

[racerone]

Step # 1 on those is a compression test.-----Post your numbers.---Spark should jump at least a 3/8" gap on a test device--Run with a timing light one cylinder at a time to see if it is an ignition miss.----Could just be a bit lean on carburetors at idle.

 

[F_R]

Get rid of those surface gap plugs and use Champion QL77JC4 plugs gapped at 0.030"

 

[HypnoCraft]

Thanks for the input. I cleaned the surface the plugs and the engine runs way better at idle. I swapped to your recommended plugs and it runs even better.

I reset the 4 idle mixture screws and idle rpm. Everything seems to run properly, but I won't know until the boat is in the lake next.

Compression was 120 across all cylinders.

I will be happy if it was just the plugs.

 

[jimmbo]

Going to a Regular Plug from a Surface gap, places the Spark deeper into the Combustion Chamber, effectively advancing the timing, so the engine will idle a little faster. How it affects the Flame Front at higher Speeds I don't know

 

[HypnoCraft]

Going to a Regular Plug from a Surface gap, places the Spark deeper into the Combustion Chamber, effectively advancing the timing, so the engine will idle a little faster. How it affects the Flame Front at higher Speeds I don't know

Hmm, yeah, I didn't think about that too much. Maybe I will back off the maximum advance an 1/8th of an inch or so, just so I'm not going past the recommended advance.

 

[jimmbo]

Myself, I would back it off 4 degrees, see how it runs, and then readvance the timing in 1 degree intervals, listening carefully for Preignition/Detonation