1978 Johnson 70HP head scratcher

[billythegrape]

Did you check the flywheel magnets to be sure none were loose and just stuck on there. Also wondering about the trigger coils. Maybe do a resistance test on them while wiggling the wires. This ain't that complicated.

Yes I tried the magnets. Will ohm test the triggers and get back.

 

[billythegrape]

As soon as pressure from the back side hits it, it should close of unless something is in there. Check to be sure foam from the bonnet or maybe a bug carcass is in there. . I've worked on outboards for 35 years and can count on a half a hand the number that had reed issues.

I know, it's supposed to be pretty uncommon.

I checked for debris; nothing there, they are clean. Like I said, just the first cylinder is leaking, but it does it consistently. And that's the one with the reed hung open, even if it's a pretty small opening.

 

[racerone]

I doubt there can be loose flywheel magnet on a 1978 motor.

 

[RBoyd1971]

I guess that's true since they are not glued on but molded i into the flywheel. Just thinking out loud without thinking. Ha ha. Can't figure out though, how the timing could possibly change by 90 degrees and the coil on #1 not fire, then go back to normal. This whole thing doesn't make sense.

 

[RBoyd1971]

When you put the #1 cylinder at top dead center is the pointer pointing at TDC on the flywheel?

 

[Faztbullet]

Seems you know all the answers but reeds will not cause rich running. If reed was bad it would blow crankcase compression out the carb. Also a cylinder leakdown has nothing to do with anything behind piston ,just piston and rings. Good luck finding your solution.

 

[billythegrape]

When you put the #1 cylinder at top dead center is the pointer pointing at TDC on the flywheel?

Yes it was, but I will check again. The key and keyway are fine, also. My timing light is old, so who knows, maybe it got crossfire interference. I haven't been able to replicate it since then, and I don't think a powerpack would cause that.

 

[billythegrape]

I guess that's true since they are not glued on but molded i into the flywheel. Just thinking out loud without thinking. Ha ha. Can't figure out though, how the timing could possibly change by 90 degrees and the coil on #1 not fire, then go back to normal. This whole thing doesn't make sense.

It's possible my timing light is fried. It's approximately one billion years old.

 

[billythegrape]

Despite amazing wisdom to the contrary, I ordered new reeds. The service manual says an allowance of 0.010" is ok, but I had read elsewhere that if you see light through them they are bad. I figured I was already in there so... I had to order new intake gaskets anyway to replace the ones I took off.

Got a chance to test things with my DVA today. Took a minute to figure out how to make it work, but I got it. The service manual from 1978 says to use a neon test light, but I don't have one of those, so I was able to get a DVA reading for this engine from CDI Electronics. Here're the readings:

Stator- supposed to be 150V-400V, my reading was 295V, well within spec; it's brand new, so not surprising.

Timer base output- supposed to be 0.6V+

Sensor 1- 1.54V
Sensor 2- 2.7V
Sensor 3- 2.3V

These readings appear to be in spec. According to the CDI guide, "The trigger signal rides on top of the high voltage on these timer bases. Check stator DVA first. Then if timer base DVA is 0.6 - 2.5 V, the pack is faulty."

This is exactly what I did. Two of the readings fall within this guideline, one does not. I tested three times and got the same results.

It goes on further to say, "Check the DVA voltage on each Black/White wire to engine ground. You should have a reading of at least 150V or more (while connected to the pack). If the reading is low, disconnect the timer base wires from the pack and recheck the Black/White terminals ON THE PACK. If the voltage jumps up to an acceptable reading, the timer base may have a problem in the internal wiring (possibly a thin spot in the insulation on one wire)."

I did this, and got approximately 0.9V on each wire when connected. Then I disconnected them and got pretty much the same thing. This would lead me to believe that the timer base is ok, and that the power pack is dead or on its way.

Thoughts?

 

[billythegrape]

Called CDI, they said to DVA the coil wires out of the power pack. If below 150V, replace the power pack. They had nothing, so I guess it's the power pack.

 

[billythegrape]

Ok an update. Here's what I've done.

Replaced the power pack. There was 0v from the power pack to the coils using a DVA. Now the boat fires right up, practically the first turn of the key. Replaced the spark plugs. They were NGK, got the proper champions in there and correctly gapped. Now everything tests ok.

Took the boat out, it really wants to go, but acts like it's starving for fuel.

Replaced the clapped out fuel tank and replaced the lines, primer bulb, and the fittings. Wentout again, boat went along ok, but after a but suffered a lot of sputtering and stuff at WOT, pumping with the primer bulb didn't seem to make a difference. Plugs are not fouled, but there did seem to be some smoke and gas in the water.

Replaced lines on carbs with new stuff. Tested fuel pump.

With output hose off, fuel comes out, but it's pretty weak. Like a little stream at the bottom of the hose. Pulse nipple has strong pulses. Put my snap on fuel gauge teed into output, pressure is very low. The gauge measures in 2 4 6 8 graduations; it barely makes it above 2.

I'm thinking the fuel pump is bad. Yes, I replaced it previously, but I was an idiot and cheaped out on it with a 20 dollar one from amazon. Any thoughts?

 

[Faztbullet]

Yep...bad reeds take out packs............NOT

 

[billythegrape]

Thanks for the input. I check where the diagnosis leads me, not listen to some hillbilly on the internet.

 

[flyingscott]

So if pumping the primer bulb did not make a difference, why the new fuel pump?

 

[billythegrape]

That's what I'm confused about. I can't exactly say either way whether it's making a difference, but it failed a pressure test. It's a knock off pump so that's my suspicion.

 

[racerone]

You are soon going to have a motor that runs fine.

 

[oldboat1]

Might remove screw plug on the front of each carb bowl, and blow some carb cleaner through each of the h.s. jets in behind the plug.

 

[Faztbullet]

Hillbilly told ya it wasnt reeds..but you just had to chase that rabbit. Rebuild the original OEM pump