70ESL75E have fuel, spark, and comp...no start

[ronward]

I just picked up this '75 Johnson 70 and put it on my boat. Compression is 110 on all three cylinders. I know that's a little low but it runs and I'm hoping a decarb will fix that since it had been sitting. I put a new impeller in and hit the water yesterday. Runs fine with maybe 1/3 throttle but bogs past that. Automatically I'm thinking a dead cylinder. I get it home and sure enough drop test shows number one is dead. Swapped coils, same thing. OK, faulty power pack. On goes the new power pack and 3 new coils, plugs, rectifier (already had the parts on hand and was planning on putting them on anyway). Now I have great 7/16 spark on all three, plugs are wet with fuel but it won't start. It ran on 2 cylinders just a couple hours earlier and now it won't even start with all 3 firing. The prior owner told me he went through the carbs but I kinda doubted he really did. My best guess is that maybe some trash got stirred up in the carbs and now it's not getting ENOUGH fuel. Is it possible to have spark on all 3 cylinders and some other electrical issue won't allow it to start? Remember it ran just a couple hours earlier and there were no other changes other than what I listed. I already removed the carbs and will clean and install new kits. I'm hoping someone can shed some light on this or agree that going through the carbs should probably fix it.

 

[racerone]

Check the wiring going to the powerpack and to the coils.----Possibly mixed up.----Checked flywheel key ?

 

[ronward]

I'm positive it is wired correctly. I labeled the wires as I took each one off. Even checked again after the no start, wiring is right. Can you tell me what could have happened to the flywheel key? It ran earlier, it ran to do a cylinder drop test. It idles great on two cylinders so I can't imagine anything could have happened to the key. Certainly not doubting you but just trying to understand your train of thought.

 

[David Young]

You might want to rebuild the fuel pump while your doing the carbs.

 

[flyingscott]

A flywheel key can shear for many reasons and it will happen suddenly so yes check the key.

 

[ronward]

Good enough, I'll pull the flywheel this morning. And I'll probably do the fuel pump when I do the carbs

 

[krakatoa]

Maybe a faulty powerpack?

 

[ronward]

I put the old power pack back on because I knew it would fire 2 of the 3 cylinders, still nothing. Still working on removing the flywheel right now, it's being a bit stubborn.

 

[ronward]

Update... Finally got flywheel off after much heat, a puller and rubber mallet. I think it's been on there for 41 years. Everything looks great, key is intact. Stator "looks" good, no leaking goo and looks almost new. Working on carbs now. Any other ideas anybody?

 

[oldboat1]

might clean and regap the plugs. Set them for .030 -- believe OMC had recommended .040 for a while ('80s?) but returned to the .030 setting. Spark testing as you did is absolutely correct -- but doesn't tell you the plugs are firing, unfortunately. It's a tad unlikely you have three bad plugs, so thinking maybe the gap.

 

[ronward]

I mentioned in post #1 the new plugs. I have 3 brand new Champion L77JC4 plugs gapped at .030 in it. I wish it were that easy but just to be sure I put my original plugs back in just to be sure (I know they were firing). There's no way I have 6 bad plugs. I got the carbs done, putting them on now and will post results shortly. Thanks to all replies

 

[ronward]

Carbs clean as a whistle, re-installed...still no go.

 

[oldboat1]

Spray in a little premix and see if it fires. Or use a little starting fluid to see if it will at least pop.

 

[ronward]

I'll try that right now. I did pour seafoam into the cylinders and let sit for a good bit...compression has come up to 120,getting better.

 

[ronward]

oldboat1 premix did not do a thing. I'm lost and about to take it to someone. I love these older motors but never had one kick my tail like this one.

 

[oldboat1]

pretty well juiced with seafoam and all, but still should pop -- assume you are injecting directly into the cylinders, and cranking at a good clip. Know it's heresy, but would use a little starter fluid, if you have some. And...just to be sure, would pull out the tester again and check for spark.

 

[ronward]

First off, thank you and everyone for their input. I have done everything that has been suggested with the exception of rebuilding fuel pump because I do not have the parts available. Battery has a fresh charge and is turning the motor fast. Mix sprayed directly into each carb. Do not have starter fluid on hand but can get some tomorrow if that might help solve this problem. And yes I have pulled out the tester several times and there is good blue 7/16 spark on all three. My only uncertainty is how often is a brand new rectifier bad and could that cause my problem?

 

[flyingscott]

starter fluid won't help so don't use it if it's not firing a fuel mix it's not going to fire. Do you have the coil wires connected correctly

 

[oldboat1]

starter fluid won't help so don't use it if it's not firing a fuel mix it's not going to fire. Do you have the coil wires connected correctly

covered wiring, but good to recheck. Inject directly into cylinders, not via the carb. Your call on starter fluid for testing -- can work for tough cases.

 

[ronward]

Have re-traced coil wires and they are correct. Assuming they are in order top to bottom same as the cylinders are. oldboat1 I understand now that you mean to take plugs out and spray. Will try that.