1973 Johnson 50ESL73R very low power

[Captain Bravo]

This motor is severely lacking power at anything more than 1/3 throttle. This is what I have done. New spark plugs, stator, rectifier, timer base with sensor, cleaned and adjusted carbs, cleaned and inspected fuel pump, replaced all fuel lines & bulb, and has fresh gas. Timing is perfect, throttle is opening all the way, compression is 155# both cylinders. Throws a bright blue spark 7/16". Honestly everything I check on this motor tests out as perfect.

It was (supposedly) rebuilt a few years ago. When I first got this engine it ran great for about 20 minutes. Then it started losing power at higher throttle settings. Last fall, it would start and run fine at idle and high idle. It would stay running at full throttle, but it didn't have any more power than half throttle.

This spring, it doesn't want to idle well, and it seems to be lacking power even more than last year. To start, lift warm up lever, choke it for a few revolutions, and then let off the choke. After it starts let it rev a little, then drop the warm up lever with one hand and advance throttle with the other. It will usually go, but is severely lacking power.

I wondered about a crank seal, but the spark plugs look OK, and there seems to be a good pressure pulse at the fuel pump line. Here is a link to pics of the spark plugs and short video of the pressure pulse.

http://s172.photobucket.com/user/Maggsters_pics/library/50hp Johnson 50ESL73R

What else should I check?

 

[mfkadz]

One plug looks dry and the other wet. You said the timing is good. Have you put your timing light on cyl 2 to see how it's doing? If your light flashed on both. Disconnect one plug wire at a time and see what happens. It should run the same way both ways. If you notice no change with 1 and can't make it go on the other it's fuel related.

Also, those green coil packs are old. You might try running it in the dark and see if the wires are leaking to ground. Lovely power robbing blue arcing.

mike

 

[Captain Bravo]

OK, no leaking spark. The engine wouldn't start at all with coil 2 unplugged, and ran the same with coil 1 unplugged as it did with both plugged in. So 2 questions.
1. Do you recommend changing the coils because of the age?
2. The carbs have both been gone through very carefully multiple times. What would you recommend I look for ?

Thanks for the help.

 

[mfkadz]

Ok, no leaks is good.

It's either gas or spark for cyl 2. You can swap the coils and see if cyl 2 starts working and Cyl 1 stops.
If the problem moves it's the coil.
If no change the coils are good and it's most likely a fuel problem.

mike

 

[Captain Bravo]

I will try to check that this evening after work. Thanks for the help.

 

[Captain Bravo]

I finally made it back out to work on the motor. Started by swapping plugs, then swapped coils, and there was no difference. Then I left the plug wire off the top coil ( the one that the engine would run on) and tried spraying fuel mix into the lower carb. It started and died right away. Long story short, it wasn't getting fuel into the lower carb. A good cleaning of the fuel inlet and the needle valve and now it will run on either coil. Since the problems usually showed up under load, I am hesitant to call it until I get the chance to get it on the lake, but it definitely seems better.

Thanks a lot for the advice Mike.

 

[mfkadz]

Super, no problem. I need to finish moving the mulch on my drive before I can test my fix. New spark plugs.

mike