Johnson 110HP Running Lean?

Wondering how I can tell if I am running too lean, don't want to blow the powerhead again. My spark plugs on the bottom 2 cylinders have ground electrodes that are almost white, while the upper two cylinders plugs have ground electrodes that are brown. This is only after 4 hours on the plugs, most of it at 3500 to 4500 RPM, only about an hour at low speed. Any idea how do find out if it is a lean problem? Engine is 1986 110HP, running VRO which appears to be working fine. Would I be best off to add some oil to my gas as well until I get this resolved? Maybe I worry too much. Pics of plugs on another recent thread that didn't yield too much info. Thanks, Mark

Re: Johnson 110HP Running Lean?

Clean the plugs then pull the lanyard line and turn the motor over for a a few seconds. pull the plugs and check they are all wet

Re: Johnson 110HP Running Lean?

You are asking a very valid quesion. Your issue would be of significant concern to me. The color difference on your plugs seems to be related to your carbs. The top cyls are fed with one carb, the two bottom cyls with the other. For some reason the lower plugs sound like they are running leaner. Usually a VRO issue would affect all 4 cyls equally-so that's probably not it. Has the bottom carb been off for overhaul at some point? Have you visually inspected the all 6 jets in the bottom carb? Any chance both carbs have plastic bowls?

Re: Johnson 110HP Running Lean?

I have not pulled the carbs. The carbs were off during major powerhead work 2 years ago and were supposed to have been gone over. Carbs have metal bowls. Guess I need to be reading up on carbs.

Re: Johnson 110HP Running Lean?

I'm thinking get a pair of rebuild kits and redo the carbs. Save the powerhead. Pick up an OEM manual and follow the instructions if you don't know how to do it. It can't hurt. Make darn sure alll the jets are clean, clean, clean and that the floats move freely and seat properly. Set them with the carb upside down!!
Do your homework on here too!! LOTS of threads on carb rebuilds.

I have an '87 Evinrude 110 and she was having a carb run lean. Threw in a couple rebuild kits and it straighten out. I was having power loss issues at higher speeds. Did some investigating and found the lower carb was varnished up. An OEM manual is prolly the best investment you will ever make.

Re: Johnson 110HP Running Lean?

I think I'm going to throw in a new set of plugs and do a controlled test of everything without risking blowing the motor up ... then do an evaluation. I've got the original factory service manual, but in my older years, I'm not as quick to jump into rebuilding things, like in the 60's when I'd rip anything apart, just for fun. The rebuild of the carbs looks simple enough, but the synchronization/timing issue may scare me off. Thanks for the comments, Mark

Re: Johnson 110HP Running Lean?

Update: Had the carbs pulled/cleaned/checked. There was a small amount of dirt in the bottom carb, but nothing that was considered significant. Both carbs were cleaned. Some small diameter hoses were also replaced due to cracking. After being put back together, the engine was run in a test tank for 10-15 minutes at low RPM. Following the low speed run in tank, the plugs were of a similar appearance and wet. I put in a fresh set of plugs (QL77JC4) and took the boat for a 45 minute run. Most of the operation was 3500-4000 RPM, maybe 15 minutes at idle RPM. Finished up with 5 minutes at idle RPM. Back at the dock, pulled the plugs and the lower 2 plugs still appear dryer than the upper two plugs and the ground electrodes still have a silvery/white appearance. The engine runs great over the entire throttle range, just have Cylinders 3 & 4 with plugs that look like it's running lean. Oh, compression is uniform, 120# on all cylinders.

Ideas?

Re: Johnson 110HP Running Lean?

When the lower carb was apart, were all the jets in the carb removed and visually inspected? Does not take much debris in the jet to restrict fuel flow. Esp, any dirt/debris tends to settle in the main (high speed) jet in the sides of the carb bowl-since they are at the lowest point in the carb fuel system.

Re: Johnson 110HP Running Lean?

Yep, all jets were removed and cleaned. Jets were all checked to make sure that they were the same in both carbs. All varnish was removed and everything was made squeeeeky clean. I didn't do the work, a trusted mechanic did.

Re: Johnson 110HP Running Lean?

Have you checked the vacumn/ recirc lines for leaks?

Re: Johnson 110HP Running Lean?

Recirc hoses were replaced when carbs were gone through. They were starting to deteriorate.

My next step to to run a small tank of new gas that contains NO additives at all. I will also be monitoring (while running 3000RPM+) the temperature on the cover plate adjacent to the plugs just to confirm that it isn't getting too hot in that area.

Not sure if I'll find anything.

Re: Johnson 110HP Running Lean?

You can have one or more cylinders running lean and you may not observe any overheating issues with a laser temp gun-focused on the head. As long as the cooling system is functioning, it will likely keep the engine cool. Lack of enough cooling fuel/oil will cause an internal cylinder overheat which may not be detected.

Re: Johnson 110HP Running Lean?

I'm back. Finally the winds in Erie subsided long enough for another trip on the water, not long enough, but enough to find out a few things. - I ran this time with a separate 3 gal tank with unadulterated fuel, but with a 100:1 premix. I'm running the VRO as well. Ran 45 minutes, equal parts idle RPM (in gear), 1000RPM and 3500RPM (too rough to run above that). Plugs #1,2,3 all had insulators around the center electrode that were gray/brown and ground electrodes that were light brown. Note; these plugs only have 2 hours on them. Plug for #4 cylinder had an insulator color that was black and the ground electrode was again almost white at the very tip, as if it was very hot. Before, it looked like the problems were the lower 2 cylinders, now it looks like it is #4 only. Any chance that there is something that causes #4 plug to run hot? Something in the coil or power pack?

And maybe I haven't given this thing enough time to settle out. Or, maybe I'm being a bit anal. Having blown a cylinder or two will make a person that way.

I'm guessing that my fuel additive was responsible for the very white appearance of the insulators previously. I'm not concerned about running lean any more, just the appearance of #4 plug. My temps on the cylinder head covers match up with the thermostat temps, so I'm not going there again. Temps are all good. Puzzling now why the black insulator (almost glazed) and the white gnd tip.