1968 Evinrude 18hp fouling bottom plug

[james__12345]

I have a 1968 Evinrude 18hp fastwin, that keeps fouling the bottom plug. It doesn't take but about five minutes of running with new plugs in for the lower plug to be COVERED in carbon. The top plug is fine. I have replace the coils, points, condensers, and plug wires so far and its still fouling the plug out as fast as I put one in it. Does anyone have any idea what could be making it do that? I've heard on some motors, the fuel pump being bad can do that, but on this motor, the fuel pump looks to be on the top cylinder, so I dont think that would be the problem, but I'm not sure.

 

[kbait]

Re: 1968 Evinrude 18hp fouling bottom plug

Make sure the bottom cylinder has adequate compression.. just pull the rope slowly and if the pulses of the two cylinders feels the same, you're likely good there. Also, make sure the bottom plug lead will produce a consistent 1/4" spark on a tester (or an old plug w/gap WAY open). If that's good too, and the bottom plug is new/good, then perhaps a leaf (reed) valve for the bottom cylinder is faulty, or a bad powerhead seal? I'd for sure check compression, spark quality, and try a new plug (j4c or j6c champion) first.

Good luck!

 

[james__12345]

Re: 1968 Evinrude 18hp fouling bottom plug

Make sure the bottom cylinder has adequate compression.. just pull the rope slowly and if the pulses of the two cylinders feels the same, you're likely good there. Also, make sure the bottom plug lead will produce a consistent 1/4" spark on a tester (or an old plug w/gap WAY open). If that's good too, and the bottom plug is new/good, then perhaps a leaf (reed) valve for the bottom cylinder is faulty, or a bad powerhead seal? I'd for sure check compression, spark quality, and try a new plug (j4c or j6c champion) first.

Good luck!

I checked compression with a compression gauge, its fine (110 best i remember, both cylinders were the same with in about 2 or 3 pounds) I haven't actually checked the spark, but the entire ignition is new. I'll still check that next anyway though. As far as new plug, this is the fourth new plug it has done that way, two before the ignition rebuild, and two after. The first time the part store guy gave me j8c plugs when I had just gave him the old plug to get a match for it (the plugs in it were not champion plugs), the next time I got j6c after I found out that's the suggested plug.

 

[james__12345]

Re: 1968 Evinrude 18hp fouling bottom plug

Checked the spark. It will do 1/4 easy. It will jump 1/2 pretty consistent, so spark isn't the problem. Whats next?

 

[james__12345]

Re: 1968 Evinrude 18hp fouling bottom plug

Checked the fuel pump, and it's bad. I took the two screws out and pulled the pump off the motor, when I squeeze the primer bulb, fuel comes out the back of the pump. Would that be the source of the plug fouling? It looks like the pump links to the upper cylinder, but the bottom is the one thats fouling out. . . .

 

[nwcove]

Re: 1968 Evinrude 18hp fouling bottom plug

top cyl is probably getting to much fuel for combustion to take place so that plug is staying clean, and its quite possible that your carb is set a bit rich and fouling the bottom. get your fuel pump issue sorted out and see what that does for you.

 

[james__12345]

Re: 1968 Evinrude 18hp fouling bottom plug

I tried pulling one plug wire at a time to see what each cylinder would do. The upper cylinder will keep running fine. The lower will run for a few seconds then slowly die. It definatly runs better on only the top than on only the bottom. That would lead me to think the top is running fine, but I'll see in a few days after the pump kit gets here.

 

[kfa4303]

Re: 1968 Evinrude 18hp fouling bottom plug

Hi James. The fact that it dies when running on the lower cylinder only, then that means you're losing spark. If the spark plug is ok, then you'll need to remove the flywheel and inspect the ignition components. Here are some great links that can walk you through the job.

Maintaining Johnson E & FD Serie
1968 Evinrude 18802M 18 hp Outboard Motor Parts
3 HP Evinrude Lightwin Ignition System Tune-Up 1952-1967

 

[kbait]

Re: 1968 Evinrude 18hp fouling bottom plug

Did I mention faulty leaf valve?

 

[james__12345]

Re: 1968 Evinrude 18hp fouling bottom plug

Hi James. The fact that it dies when running on the lower cylinder only, then that means you're losing spark. If the spark plug is ok, then you'll need to remove the flywheel and inspect the ignition components. Here are some great links that can walk you through the job.

The ignition is brand new. I just installed it, haven't even had it on the water yet. I put in coils, points, wires and all. The spark plug is not ok, its EXTREMELY fouled and gets that way literally in a matter of minutes. The spark on the lower cylinder will jump a quarter inch gap no problem whatsoever, and will jump a half inch pretty well. It doesn't die right off, its more like it bogs down and slowly dies. It fouled the plugs out just as bad just as quickly before I redid the ignition as it does now. Redoing the ignition did NOTHING to help the fouling problem.

 

[Rick.]

Re: 1968 Evinrude 18hp fouling bottom plug

Some years ago I had a 9.9 doing the same thing. kbait might have nailed it. After checking everything over and over I pulled the reed plate and found a piece of the slow speed knob (actually 1/4 of it) stuck in a reed. Told another, at wits end, guy about it once and he found a piece of zip tie in his reed. I'm not saying that's your problem but at this point it sounds like it's worth a look. Best of luck. Rick.

 

[james__12345]

Re: 1968 Evinrude 18hp fouling bottom plug

Some years ago I had a 9.9 doing the same thing. kbait might have nailed it. After checking everything over and over I pulled the reed plate and found a piece of the slow speed knob (actually 1/4 of it) stuck in a reed. Told another, at wits end, guy about it once and he found a piece of zip tie in his reed. I'm not saying that's your problem but at this point it sounds like it's worth a look. Best of luck. Rick.

I've read about those two cases on here when I was searching about this. I know for sure that the fuel pump is bad, after reading on here how to test it, so until I get that fixed, I really wont be able to go any further on figuring out what it is. I hope that fixes it, but if it doesn't, the reed valve seems to be my next step. At this point I don't know much about how to get to it to check it, but if it comes to that, I'm sure there's some instructions on here some where. I have a feeling once i get done with the lower seal kit this motor also needs (which is coming Tuesday along with the fuel pump kit), that shouldn't be much harder of a project.

 

[james__12345]

Re: 1968 Evinrude 18hp fouling bottom plug

I got the fuel pump rebuilt today. It seems to have fixed the problem. It runs much better now. The lower plug still comes out black, but it rubs off unlike before. I'm assuming that's just left over carbon in the cylinder from when it was fouling the plug out so bad so quick. I think a decarb will solve that. I didn't think to try running on just the lower cylinder yet, and went ahead and started on the lower seal kit. I'll post another update after I get the seal kit done, and get it out and actually run it some.

 

[kfa4303]

Re: 1968 Evinrude 18hp fouling bottom plug

Glad you got it running. A good decarb followed by a nice long WOT run on the open water should help with the plug fouling. You can even step up the plug to a Champion J6C which is a bit hotter than the J4C.

 

[james__12345]

Re: 1968 Evinrude 18hp fouling bottom plug

I'm already running the J6C. I found out yesterday I am having a little bit of a problem with the carb though. I had forgot to check to see if the primer bulb got hard after I replaced the leaky fuel pump. It still doesn't get hard, and will pump until gas runs out the front of the carb. Seems like the float is sticking or something. I guess once I'm done with the low end seals, I'll be starting in on that.

 

[kfa4303]

Re: 1968 Evinrude 18hp fouling bottom plug

Two steps forward, one step back. The fact that the primer bulb doesn't get/stay firm when you prime it usually means the fuel pump, or the primer bulb itself is bad. A stuck float needle usually causes the carb to flood. Here's a carb rebuild link that may help. It's for a slightly different model, but all of the steps are the same.

5.5 HP Evinrude Johnson 1954-1954 Carburetor Tune-Up Procedure

 

[james__12345]

Re: 1968 Evinrude 18hp fouling bottom plug

I just redid the fuel pump, and it checks out ok. I also checked the primer bulb by squeezing it with it not connected to the motor, and it stayed hard and wouldn't squeeze at all hardly, so the bulb and check valve are ok. When hooked to the motor, the bulb does get somewhat firmer after a few pumps, but never very solid. The motor ran pretty smooth when I had it out, just didn't have the power it should have (which I assume was tied into the plug fouling so bad), so apparently whatever is going on with the carb isn't horribly bad. The bad news is, my 847 still isn't here yet, and I'm leaving for vacation next weekend, and have a LOT of work to do next week before we leave, so I most likely wont get to get it out on the water for a couple weeks. I may go ahead and get the carb kit ordered because I should still have time after work to get it installed, and have this motor really tuned up before I finally take it out again.

 

[james__12345]

Re: 1968 Evinrude 18hp fouling bottom plug

I got the rebuild kit, and when I took the carb apart the float was trashed. Its the old style varnished cork, and the finish was cracked and peeling off, and the float was soaked full of gas. The float was also way out of adjustment. That seems to be the source of the bulb not getting hard, because I laid the float out in the sun for a few hours to dry it out, and adjusted it, and put it all back together (with the new needle and seat) it works like it should. I think the reason the float was so out of adjustment is that the float needle was a rubber tipped one, but it didn't have the groove in it for the spring. I think it may have been sticking before, and whoever worked on it before was trying to lower the float to get the needle to drop. Unfortunately I ordered the wrong float, and I am waiting on the new one to come in.

Everything inside the carb was spotless, with the exception of the low speed needle packing being a wad of mush. I dont know how long ago the carb was worked on, but it had clearly been worked on before, because the high speed nozzle was bent up from someone trying to take it out with a screwdriver. I'm not sure if it was so clean because someone had cleaned it recently before I got it, or if the seafoam I run in it is the reason it was so clean, but it was perfect inside.