Running on one cylinder. I'm at a loss.

[i386]

Today I'm back at it with the 33HP Evinrude. I was hoping to get the high speed jet dialed in today but that was not meant to be.

Got her on the lake. Not enough power to plane at all. Top cylinder is cold bottom one is warm. Remove the top plug wire and it diesn't run any different. Remove the bottom one and it won't run at all. Ok Fine. Limp back to the ramp and go back home. 5 minute drive. Remove the plugs and spark test both cylinders. Both look good. Try to run it in a bucket. Reluctantly starts. Pulling the plug wires one at a time reveals it will now run on the top one but die if I try to make it run on the bottom one. Yes you read that right. Completely opposite problem than I had on the water.

Motor is hard to start today and backfires out the exhaust a couple times before it decides to fires up and run. Runs smooth once it's going. Too smooth. It's hard for me to tell when it's only running on one when it starts up on one.

Points and condensers are brand new.

 

[Joe Reeves]

Re: Running on one cylinder. I'm at a loss.

What is the model number of that engine?

Remove the flywheel and inspect as follows.

Does the armature plate (plate the points attach to) wobble, move side to side, up and down on any side, or is it solidly secure and moves only in a circular movement?

Backfires out the exhaust = Either the plug wires are now crossed OR the flywheel key has sheared due to the flywheel nut not being torqued to factory specifications ie 105 foot pounds...... however, it would be impossible for the engine to run in either scenario.

 

[58rude]

Re: Running on one cylinder. I'm at a loss.

Maybe one of the clips on the end of the pug wires is not making a good connection. Spary a little WD40 down in the boots and pull the boots off the plug wires . Then trim a little bit off the wires and push the pins back in. Then go ahead and take some ohm readings from the clips to ground and see what you got.

 

[kfa4303]

Re: Running on one cylinder. I'm at a loss.

Hey i386. I have a 33 hp too. I know you said the coils and points are new, but perhaps the s'plug wire which connects/twists on to the coil is bad. That happened here in the forums to a guy with similar problems the other day. Since you said lack of spark seemed to move around, makes me think that s'plug wires may be a bit loose. Double check magneto and make sure everthing is tightened down, and the wires are tucked safely out of the way of the cam. Just a thought.
When you say you "tested spark", how did you do so? Did you use a gap tester, or the just ground the plugs on the engine and look and listen for a "snappy" blue spark. I ask b/c you may get a spark out of the plug which looks ok, but is not actually hot enough to ignite properly.
Another thought is that the hi speed needle may partially to blame for poor starts and lack of power. Make sure there are no air leaks in or around the carb or needle. That happened to me recently and it was a beast to start the motor, until I tightened all the screws on the carb and air silencer and then Bingo she started right up. Keep us posted. We'll get her running.

 

[i386]

Re: Running on one cylinder. I'm at a loss.

What is the model number of that engine?

Remove the flywheel and inspect as follows.

Does the armature plate (plate the points attach to) wobble, move side to side, up and down on any side, or is it solidly secure and moves only in a circular movement?

Backfires out the exhaust = Either the plug wires are now crossed OR the flywheel key has sheared due to the flywheel nut not being torqued to factory specifications ie 105 foot pounds...... however, it would be impossible for the engine to run in either scenario.

Thanks Joe, It's a 33953A. Checking for play in the armature plate is one thing I have not specifically checked. There is a small piece of metal crimped to the top plug wire as a marker. That's always my reference that I have the plug wires connected correctly. The flywheel is tight, possibly more than the required torque. I have not yet properly torqued the flywheel nut with my torque wrench because I needed a 3/8 to 1/2 adaptor in order to use that big socket on my torque wrench. I have one now and will properly torque after I check the armature plate for play.

Hey i386. I have a 33 hp too. I know you said the coils and points are new, but perhaps the s'plug wire which connects/twists on to the coil is bad. That happened here in the forums to a guy with similar problems the other day. Since you said lack of spark seemed to move around, makes me think that s'plug wires may be a bit loose. Double check magneto and make sure everthing is tightened down, and the wires are tucked safely out of the way of the cam. Just a thought.
When you say you "tested spark", how did you do so? Did you use a gap tester, or the just ground the plugs on the engine and look and listen for a "snappy" blue spark. I ask b/c you may get a spark out of the plug which looks ok, but is not actually hot enough to ignite properly.
Another thought is that the hi speed needle may partially to blame for poor starts and lack of power. Make sure there are no air leaks in or around the carb or needle. That happened to me recently and it was a beast to start the motor, until I tightened all the screws on the carb and air silencer and then Bingo she started right up. Keep us posted. We'll get her running.

I have a proper spark tester and also an in-line tester for testing while running. The plug wires look brand new to me. I think they're too short to cut off and re-pierce. I will keep your suggestions in mind.


The points and condensers are new and gapped properly. It's clean enough to eat off of under that flywheel. I just rebuilt the carb with an OMC kit. It looks brand new.

I started to pull the flywheel today but something told me to leave it alone for once. Then it occurred to me that I didn't pay attention to which cylinder I took which plug out of. The problem could have followed the plug from one cylinder to another. So I bought new plugs. She fired right up in the bucket so back to the lake I went.

Some of you may recall me troubleshooting performance issues with this same motor. Well today with those new plugs she got on plane faster than ever. There was enough power there that I could back off the throttle a little and stay on plane. I ran about 5 gal. of gas through her this time with no problems. I'm not 100% sold that it was the plugs, but I believe it was a big part of it.

Now back at the ramp she was getting reluctant to shift into reverse so we'll see where that goes.





It's tough identifying and working these problems out. Nothing on this boat worked when I got it so I am trying to learn what everything feels like when it's right. I don't really have a group of boating peers so you guys are it. I really appreciate it.

 

[kfa4303]

Re: Running on one cylinder. I'm at a loss.

sweet! glad she's running and that it was a cheap and easy fix. sometimes the most obvious answers are best.

 

[boobie]

Re: Running on one cylinder. I'm at a loss.

It's the little things that will always get you and never trust "new" spark plugs because they are new. Been burned on that one years ago.

 

[samo_ott]

Re: Running on one cylinder. I'm at a loss.

Strange. I got my first (1969) 33hp 2 weeks ago and I got it running also and then it dropped one cylinder. Mine turned out to be the plug also... Quite rare... Huh.