1976 35 HP Evinrude low rpm's in forward

[drsaxman]

I just graduated to trying out my new (to me) boat in the water today an I'm experiencing an issue where the motor is not putting out enough power when in Forward. In neutral, it revs normally and idles very well, and if I put it in neutral in that one spot where the motor thinks it's in forward, I can get plenty of RPM's. However, when I shift it into forward and give it full throttle, it does not want to go. I'm not sure where to start troubleshooting as it is running fine in the trash can in neutral.

Is it a bad idea to run it in the trash can in gear?
Both of the ignition coils have a crack in them. Would that cause the lack of RPM's when in forward gear?

Thanks again for your help. I would not have made it this far without this fantastic forum.

Attached are what the coils look like.

 

[boobie]

Do a cylinder drop test on it and see if it's running on both cylinders.

 

[drsaxman]

No Title

Thanks for the advice boobie, the drop test definitely revealed an issue. It looks like the top cylinder isn't firing. The motor runs when the top plug is detached but not when the bottom plug is detached. I replaced the plugs when I got the boat. I pulled the plugs and the top one looks incredibly clean. Am I looking at replacing the ignition coil for the top cylinder at this point? Photos of the plugs are below. The right one came off the top cylinder.
I also switched the spark plug wires and re-performed the test and the symptoms followed the wire. It ran when the bottom wire was on the top cylinder.

 

[mfkadz]

Swap the coils with each other and see if the problem moves to the other cylinder. If so you need a coil pack.

mike

 

[drsaxman]

Hey Mike,
Wouldn't switching the spark plug wires accomplish the same thing as swapping the coil packs? I'm definitely not an outboard motor expert, but I could see swapping the wires might create an issue with the timing, other than that, I would think it would be equivalent to flipping the packs.

 

[mfkadz]

If you just swap the plug you will be firing 180 deg out.

You can move the whole coil pack and it's connections or...

Swap the plug wires and swap the inputs from the power pack. Basically swapping without moving.

mike

 

[Chinewalker]

No power pack on that motor, it had a low tension magneto with maker points and a driver coil under the flywheel, and external coils on the head.

That said, check the point gap, check all wires. Points MUST be gapped at 180 degrees opposite each other for best running.

Do a compression check, too.

 

[gm280]

draxman, I think what mkadz was trying to say was to physically remove the spark coil from the top and swap it with the bottom one and vise versa. That way you are checking to see if the actually coil itself is the problem. You still hook the wires back up to the coils like usual in the same way. The only thing that changes is the spark coil. And if the bottom cylinder stops firing, then you proved the spark plug coil that way on the top cylinder, is he problem part... With that said, I personally would buy two new coils and be done with it. Any time a coil starts cracking, it isn't long for it to crap out... I have basically the same setup on a 1976 40 HP Johnson OB.

 

[mfkadz]

You got it gm280....

mikeski

 

[drsaxman]

Based on how different the spark plugs look, I'm guessing that the top coil isn't firing. The top one still looks brand new while the bottom one looks like it has a few explosions under the belt. Would not having the top cylinder firing also explain the oil I'm seeing in the barrel I'm starting it in? If the cylinder isn't firing, then the gas/oil mixture would be going right out the exhaust.?.?

 

[boobie]

Yes...........

 

[drsaxman]

Pleased to report the new coil arrived today. After installing, she fired up immediately. I thought she was running good before, but now she just purrs. Performed the cylinder drop test again and she passed with flying colors. Thanks for all the great advice. Hopefully I'll be fishing this weekend.