Topic: 57 Johnson RDE 19 running on 1 cyl – Page 2

This topic has 23 replies, 8 voices, and was last updated 8 years, 5 months ago by fleetwin.

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October 31, 2015 at 4:11 pm #26321
frankr
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US Member
quote lakeboater:

no mercury switch on the 57, I think the last year was 56 or it was removed long before me.
So, I just ran compression and spark tests top has 115 psi, bottom has 118 psi. I had a good arc on both cylinders 1/4 inch plus using a screwdriver to a head bolt. I’m thinking I should pull the head cover next and give it a visual. I keep thinking about that bottom plug, how white it was. Could I have a water leak into the cylinder, yet still have good compression? Any other suggestions?

Absolutely. A perforated exhaust cover baffle plate will squirt water into a cylinder (or cylinders) through the exhaust ports.
October 31, 2015 at 9:27 pm #26335
fleetwin
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US Member - 2 Years
Well, a leaky exhaust cover could surely squirt water in a cylinder and make it miss, but this surely would not be my first guess. Do you see any water droplets on the plugs? Pulling that exhaust cover is a messy job, not to mention you might have trouble getting the rusted bolts out, so I wouldn’t dive into the cover on a "guess". I would hate to see you go through all that work only to have the same problem. I’m assuming the engine misbehaves at low speeds, does the bad cylinder kick in and out, or is the engine just running on one cylinder all the time? I’m assuming you have tried another set of plugs. If you really suspect a water leak, I would suggest an easier test, assuming the engine misbehaves at idle. You could always remove the gearcase (to protect the impeller from melting) and run the engine with no water for a couple of minutes to see if it idles better.
In any event, your compression is good, so I sure don’t think your head gasket is blown. I realize you have done some sort of spark check, you might try those inline neon testers as well, to see if one cylinder is losing spark/weak while running.
I just don’t want you to get weighed down in complex issues, try all the basics first.
November 1, 2015 at 5:29 am #26357
jeff-register
Participant
US Member - 2 Years
I may suspect a reed being out of sorts. It would be sudden & all at once. Start the motor & hold a piece of stiff paper in front of the carb while running. Look for fuel/air spray back out of the carb opening. If the reed is not seating the compression will go backwards & out the carb. Just a suggestion. Not sure on the electrical problem until I trace all the wires. As old as it is anyone could have messed with the wires & where they go.
November 1, 2015 at 2:47 pm #26363
bh
Participant
If the motor is starting on 2cyls and then dropping to one as you advance the throttle , I would be looking at the two plug wires ,
with one shorting out on some metal object as they rotate rearward to full throttle, Run it at nite with the hood off,
and you will see the arcing . Common issue on most Johnsons of that era.
November 1, 2015 at 2:57 pm #26366
lakeboater
Participant
Thanks for the suggestions. The problem is more evident under a load for sure. The boat is out and away from the lake now, I think I will run it in a barrel next with the cover off and see if any thing is evident . By looking at the pictures of the plugs, which cylinder would be more suspect? The sooty one or the too clean white one?
November 1, 2015 at 4:49 pm #26371
Mumbles
Participant
Missing under load or acceleration is usually caused by a bad plug. Try replacing the clean one with a new one or known good one to see if it fixes the problem.

viewtopic.php?f=2&t=1292&p=6784&hilit=sears#p6784
November 1, 2015 at 7:01 pm #26377
jeff-register
Participant
US Member - 2 Years
Mumbles,
You just might have something with failing spark! May have a cracked insulation on your plug wires or possable top seal blowing compression out the sealing area soaking the points. Sound plasable? My 58 Johnson 18hp had a bad top seal & was getting the points too wet to fire
November 2, 2015 at 5:42 pm #26427
beerman57
Participant
Touch the mag plate while it’s running, if a plug wire is grounding out you’ll get zapped like I did recently.
November 2, 2015 at 10:40 pm #26437
lakeboater
Participant
Well, I ran the motor in a bucket this evening, no stray spark was seen even at different throttle settings. I did however get a better look at the plug wire and the cut is deeper than I thought. I did retest for spark at the plugs and had good spark. I’m thinking the wire is causing poor quality spark under load even though it isn’t arcing. The wire in question was on the top plug with the sooty look to it. I guess I’ll get into the ignition and change these wires and do points while I’m in there unless there are any other suggestions.
November 3, 2015 at 12:34 am #26450
beerman57
Participant
Don’t guess, touch the mag plate while it’s running!!!
It only hurts a little.
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