Runs great wide Open but hard to get it there

[Muddyjeep810]

Hi all. So I finally got my boat with the 1977 Johnson 70 horse back in the water after replacing all my head gaskets and exhaust manifold gaskets. Ran great on the hose in the garage. Idled good and revved strong. When I got it in the water today it was a totally different story. It basically wouldn't idle. The only way to keep it running was to have the cold start throttle lever all the way up. It would then SLOWLY build RPM's up to 2000 RPM where it would stop climbing. Any movement of the controls at this point required I turn the cold start all the way down and it would stall before I could get it into gear. So then I left it running at max cold start throttle for five minutes, and after about 5 minutes the engine sounded like it was coming alive and would climb slowly to 3000 RPM. Once it made it up to 3000 RPM I could slam the cold start throttle off, and slam the boat into forward and it would take off like a raped ape and almost immediately plane and run awesome wide open around the lake until I let off the throttle and let it get below 2000 RPM's again. It would then get really sluggish again and I would have to feather the throttle to get it above 3000 RPM where it would run great again.

I pulled the plugs when I got home and the base is kind of shiny with a very light brown haze, almost looks wet but they aren't super wet, and the electrodes are dry with a light coating of what appears to be black carbon.

Please help. I am at my wits end with this engine. I have rebuilt the carbs, replaced the plugs, replaced the lower unit oil seals (Water pump/drive shaft and shift rod only) replaced the control box, replaced both control cables, added an in-line fuel filter, replaced all the fuel lines, plus the aforementioned work. Compression is 120/118/120, and the engine bogs at idle when I pull each plug wire.

Where do I go next?

 

[Muddyjeep810]

Ok, I feel like a total idiot right now but at the same time I have this very slight feeling of hope. When I reassembled the engine after the exhaust manifold gasket repair I forgot to tighten up the positive battery cable to the solenoid.



Is it possible that the engine wasn't receiving high enough voltage to fire good at lower rpm but once I got it into higher rpm the alternator (or whatever charging device is on this engine) picked up the slack and it fired good?

 

[Muddyjeep810]

Also, I was just checking my coils with a multimeter. I set my multimeter to the 20 ohms range to check the primary's. They all tested at 0.4 ohms which from what I read should be 0.2-1.0 making the primary circuit good. Next I tested the secondary or output circuit of the coil and that's where I am getting some funky results. According to the specs I found these circuits should test between 200 and 400 ohms. So I sent my multimeter on the 2000 ohm range. I tested cyl #3 first and it tested at 1289 which is out of spec. I tested cyl #2 next and got no reading at all. When I test cyl #1 it's really weird because the multimeter reads a random/changing resistance and then instantly switches to no reading. I have seen as low as 600 and as high as 1800.

Am I doing something wrong with my testing? I have one end of the multimeter 'prongs' in the spark plug socket touching the wire element, and I have the other end where the non-grounded wire coming from the coil connects to the power pack (after removing the cover). Each coil has two wires. One goes to ground and the other goes to the power pack.

 

[racerone]

Well----12 volts from the battery is not used to make spark for the plugs.

 

[Muddyjeep810]

Well----12 volts from the battery is not used to make spark for the plugs.

I don't feel as much of an idiot now. Thank you for that LOL. Do you think my whole problem today was 2 bad coils at lower RPM's and the funky coil kicked in at higher RPM's when it ran good?

 

[Muddyjeep810]

Well----12 volts from the battery is not used to make spark for the plugs.

I read up some more on the testing and I am 99% positive I was doing it right. I took all three coils off. Put the black test lead on the coil ground wire and the red inside the spark plug socket and got no reading on one and the funky reading on the other.

 

[racerone]

Stop guessing.----Run with a timing light hooked up.----One cylinder at a time.----Observe the flashing light as you speed up the boat.

 

[Muddyjeep810]

Stop guessing.----Run with a timing light hooked up.----One cylinder at a time.----Observe the flashing light as you speed up the boat.

I don't have one

 

[racerone]

Amazing I say.------Folks are ready to buy new powerpacks , coils, stators and timer basis.----But do not have a $40 timing light ?

 

[oldboat1]

^^no flash, no spark. Does the ignition produce a 3/8" spark at each lead?

 

[Muddyjeep810]

Ok so here’s an update…. I took the boat up north but the day before I left I bought three new coils and swapped them out. The old coils tested way out of spec or didn’t test at all. I also was spraying carb cleaner around my intake manifold gasket with the engine idling “smoothly” and the motor stalled right out when I hit one spot.

So I replaced the both gaskets between the crankcase and the carbs. When I tore it down, those gaskets were like jelly in some places. I know for a fact it must have been leaking air.
I put the boat in the water first day up there. It started kind of rough but when it did start running it ran a lot better at lower rpm and didn’t stall out when I put it into gear. I could actually use reverse.

The main problem of this discussion still persisted though. It stalls out when I shift gears unless I rev it with the cold start lever to get the RPMs up, shift fast, and then give it a lot of throttle. The same goes for forward gear. It will drive in idle for a few seconds but then stalls.

At that point I took Racerone’s advice and purchased a timing light. The timing is almost dead on using the Reeves method. I think it’s one degree advanced so I didn’t touch it.

We used the boat all week up north. It runs a lot better now but it still starts hard with a lot of cranking and if you drive at medium or low rpm for 5 seconds or longer it’s almost like it loads up or maybe fouls out. It starts bogging and I have to put it back into neutral and use the cold start lever until it will hit 3000 RPM at which point I can slam the cold start lever down and gas it quickly in gear and it will run. When I am coming into a dock I have to keep goosing the throttle from neutral/idle throttle position to heavy throttle position to keep it running. The boat runs fantastic at wide open throttle. It doesn’t load up like it does at medium to low throttle.

I’m at a loss here. I’ve fixed so many damn parts on this engine. After I got home I figured I’d take a peek under the flywheel and see if I could visually spot any issues. Everything looks ok except for the timer base retainer is melted on one side. The timer base still rotates freely though you can hear a sound that almost sounds like light scratching when it’s rotating. It doesn’t feel like there is any major resistance though.

How much of an issue is this timer base retainer being melted like this? Would this possibly lead to the problems I’m having? Are there any other parts I should be looking at that a severe overheat could have damaged that would cause my issues?

Edit: When the motor was bogged out one time I hit the choke real quick and it killed the engine. It doesn't seem like a fuel issue to me.

 

[Muddyjeep810]

^^no flash, no spark. Does the ignition produce a 3/8" spark at each lead?

Yes, I checked all three cylinders with a gap spark tester and all three jumped a 7/16" gap.

 

[racerone]

Motor overheated to melt that plastic.----compression should be about 140 PSI on this motor.

 

[Muddyjeep810]

Motor overheated to melt that plastic.----compression should be about 140 PSI on this motor.

I made a new post that summarizes everything that I have fixed and found wrong with this engine. I describe the overheating and compression tests there. 120 isn't terrible for a 43 year old engine. I really don't feel like compression is my main issue.

 

[juno pierrat]

edit

 

[racerone]

I will step aside now.