My 77 Johnson 85 hp is running on half its cylinders!!

[eterry]

I took my boat out about 6 weeks ago and it ran fine.

Today I get on the lake and fire it up, it starts fine but doesnt sound...right.

I idle it down and it dies, it does this several times, which isnt usual.

I let it warm up, then engage forward and it dies again, several times...

I'm getting worried and finally get it running on water, but it run WAY under power, wont plane out, and dies everytime I idle it down.

I take cover off motor, a 77 Johnson 85 hp, and pull plug wires while its running. The bottom two cylinders arent firing.

I called a friend while driving home and we both agree it sounds like coil(s) are bad....

I FINALLY get it loaded on trailer and get it home, pop cover again and it seems bottom cylinders use seperate coils...if I'm looking right.

How can I tell if its the coils gone bad? Whats the odds they both went out the same time? Could it have run on 3 cylinders last time and me not notice?

I havent pulled the spark plugs yet, I replaced them last yr. I'll pull them tomorrow and check for wear, oil, etc.

What am I missing? Whats my next step?

Thanks,
Eterry

 

[BonairII]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

You'll need a spark tester to check for good spark. How many coils total do u have? If possible, switch one of your good coils for a suspected bad one and see if the problem follows the coil.

 

[eterry]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

If by spark tester you mean a plastic handle screwdriver to check for spark with plug out then i have that..lol. It has 4 coils, or at least looks like it, so i may see what happens if i switch one out. I'll report back after I pull the plugs and see what they look like.

Eterry

 

[emdsapmgr]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

Sometimes the bottom coil wires start to short out on the two lower cowling latches when the wires start to get some age on them. Check for shorting to ground in the dim light of early evening...

 

[guy74]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

One thing comes to mind that hasn't been said here, the bottom two cylinders share the same carb. Make sure that the float needle in the bottom carb isn't stuck and not letting fuel in. That would cause it to not make any difference when you pull either of the bottom plug wires off. Just pull one of the drain plugs on the bottom carb and make sure fuel runs out.

 

[194269]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

And while you are at it, you should run a compression check. You may have two low cylinders.

 

[eterry]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

Thanks all for the help, I am working 2nd shift so cant crank it til sunday, my next day off. the neighbors wouldnt like it if i cranked it at 0530!! I'll definately check the wires, that would be the easiest..probably. I've never even SEEN the carbs on this motor, it always ran strong and no problems w/ fuel. I'll get a compression gauge and check that also. Does this 77 model have coils, magnetos, or what? I need a manual, but like i said, never had a need for one til now.

I'll check back when I find out something. Gonna try to check carb tomorrow, maybe compression...if the 113 degree heat doesnt get me first!

Eterry

 

[emdsapmgr]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

Your engine has an ignition system that consists of a stator, timer base, power pack and 4 spark plug coils. It's considered an all-electronic ignition system. This system is separate from the battery charging system on that engine.

 

[eterry]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

Endsapmgr, what IS the charging system on my motor? I've never found out is it a alternator, a generator, or am i missing something ??

Now back to my most pressing issue...I took my boat over to a friend who has helped me many times before, and he loves to work on 2 cycle motors. He said he is pretty sure...(he'll know after more work on motor) that the power pack is out on it.

That makes sense as I couldnt imagine 2 seperate coils going out at the same time. He's also gonna check compression to see where we are on motor life.

So if it is the power pack, does anyone know a reseanable place to find one? The one guy who has a boat shop here wont even give you a kiss when you leave his shop, and I'd rather not spend my $$$ with him.

Again, thanks one and all for the info, you guys are life savers.

Eterry

 

[eterry]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

Bump

 

[iwombat]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

get or make yourself a 4-cylinder spark tester. Swap the leads from the timer base and crank it over (plugs out). Does the problem move? If so, you need a new timer base, or you need to adjust the one you have. '77 model has an adjustable base, and I have yet to see one that's close to spec with the proper spacing tool.

 

[emdsapmgr]

Re: My 77 Johnson 85 hp is running on half its cylinders!!

The stator under the flywheel has two sets of coils, one set provides power to run the ignition, the other set to charge the battery. It is an alternator, so the charging rectifier must convert from AC power to DC for the battery. Two separate and independent systems. If you are looking for some good ignition troubleshooting tips, check out cdi.com. They have some excellent tips on your specific engine.