Johnson 18 Driving Me Insane

[Thompy_04]

Ok, been working on this thing for at least 3 weeks and have come up with this. Today got it to idle almost all day long but wouldn't get up to speed. I just was courious and took the head off and no scoring or bad pistons, just alot of carbon. While trying to get up to speed I noticed some gas coming for the leg. Well I come to find out there is a little gash in the exhuast housing about 2 inches long. Gas doesn't pour out, just comes out in spurts. Also after taking a plug out to check for spark, I replaced it and it stripped the threads almost completely last 2 threads left at most. My questions are as follows. If I just weld the gash in the leg is that ok, or is the leg junk? How bad is the gash in the leg, and can it effect my abilty to plane? One more thing, can the stripped spark plug hole be repared? Thanks for all your help guys.

 

[DJ]

Re: Johnson 18 Driving Me Insane

You can repair the leg with JB Weld.<br /><br />Any machine shop should be able to "helicoil" the spark plug hole.

 

[Thompy_04]

Re: Johnson 18 Driving Me Insane

Thanks DJ, I'll get to the machine shop and get that looked at and am in the process of fixing the leg. Would the hole in the leg cause any performace loss? I'm no seaming to get spark in the bottom cylinder now after replacing all coils, points condensors and all that good stuff. The only thing left is the wires and boots. Can I buy the plug wires and boots at an auto parts store? After that it should run good, but I've been saying that for 3 weeks.... Thanks

 

[Paul Moir]

Re: Johnson 18 Driving Me Insane

Go to a small engine repair place or an outboard repair place for the wire. You'll need 7mm metal core wire, which isn't the type used on autos.<br />The auto stuff has a carbon core rather than wire, that adds a little resistance to help with radio interference. Unfortunetly, the slight resistance overly taxes these magneto systems and causes running problems.<br />Pop the flywheel off and find the problem. If you wheren't really careful with the wiring up under there, something could have rubbed and shorted out.<br />The boots on these engines are rarely a problem, but if they're rusty they should be abandoned. Pull the sparkplug wire out of them, and if it doesn't come, reach in with a pair of needle-nose pliers and grab the 'spring' and pull it out. Stab the wire with the spring makeing sure you've got good contact with the centre electrode, and push the 'spring' back in through the wire end of the boot. A little grease helps a lot with this.<br /><br />A crack in the midsection letting out exhaust should not hurt performance. Mabey your ears though. The fact that fuel is coming out through the crack indicates you are running rich or misfiring, but I guess you know that already!<br /><br />Helicoils are easy to install yourself, but you need the various tools. Most likely, the machine shop will want you to remove the head to do it, in which case you'll also need a head gasket.

 

[Thompy_04]

Re: Johnson 18 Driving Me Insane

Thanks for the quick reply, and I'll look into the wires.... As for the crack, its obvious the fuel is from the bottom cylinder, becasue its getting no spark which is letting the fuel out of the cylinder go directly out the exhaust. But the spark is weird. If I pull REAL hard on the rope I'll get weak spark. I got good spark at the house and thought I had all probs fixed, then to the marina I go with no spark. I took the flywheel off and noticed that the black wire from the coil got cut exposing the wire inside. Could this cause damage to the coil and make it necessary to replace the coil? I guess I'll just have to keep messing around. But appricate all help.

 

[Paul Moir]

Re: Johnson 18 Driving Me Insane

No, it couldn't hurt the coil. <br />Clean up the bottom spark plug's point - mabey a bit of insulation from the wire ended up in it. Also double-check the point gap. If the gap is off, you'll get a weak spark.<br />You might also want to try disconnecting the kill switch wire from that point. You don't need to retorque the flywheel to test for spark, just place it on and give it a spin.<br />It's probably something dumb - there can't be much left. Once you've got it fixed, you'll be running good.

 

[BF]

Re: Johnson 18 Driving Me Insane

When I did the ignition on my 25 hp, the same thing happened. I hadn't pushed 1 black wire down out of the way far enough, and the flywheel rubbed it. It hadn't gone all the way through, but the insulation was worn. The bare wire would probably short against the flywheel and cause your problem. On mine, I re-insulated it with liquid electrical tape, worked very slick. Then I made sure I REALLY pushed it out of the way.<br /><br />BTW, that liquid electrical tape also does a slick job of fixing up cracked rubber boots like on the "stop" button. The rubber on my starter button was cracking/going rotten... As an experiment, I painted it with 3 coats of the tape stuff and it is watertight again and feels/works much better (the coating stiffened it up, but yet is pliable). It'll need replacing someday, but it probably has years of service left in it as it is now.<br /><br />good luck.<br /><br />Brent