No spark on the left two cylinders.

[brandon.prewitt]

1986 Johnson 90 HP

Will only run 2000 RPMs in gear.

Will get up to 5000RPMs in Neutral.

I replaced the relays on the back that were arking the other day.

Now what?

 

[jbjennings]

Re: No spark on the left two cylinders.

If the two dead cylinders are on the same side and both plugs run off the same powerpack, I'd have to check that ppack.
Just an idea,
JBJ

 

[tashasdaddy]

Re: No spark on the left two cylinders.

never over 1500 in neutral. good way to blow it up, should idle at 650-750 in gear in the water. sounds like you have a bad power pack. you motor has 2 packs, 2 cylinders each. then do a link and sinc.

 

[brandon.prewitt]

Re: No spark on the left two cylinders.

What I was trying to say was I can race up the engine without a load, but not with a load.

 

[james1115]

Re: No spark on the left two cylinders.

I had the same problem a few years ago with my my 86 mercury 90 and I orig though powerpacks so I replaced them and it didnt fix, finally I found out it was the stator. Just giving you something else to check because mine was doing the exact same thing. good luck
James

 

[iwombat]

Re: No spark on the left two cylinders.

You keep racing that engine up w/o a load and you'll be using it for a parts motor after you buy your next one.

Keep it under 2k unless you're on the lake.

 

[brandon.prewitt]

Re: No spark on the left two cylinders.

Initially I couldn't get high RPM's at all without hitting the choke.

I can hit high RPM's now without the choke.

I'm not talking about WOT for extended periods of time.

 

[wildmaninal]

Re: No spark on the left two cylinders.

I had the same problem a few years ago with my my 86 mercury 90 and I orig though powerpacks so I replaced them and it didnt fix, finally I found out it was the stator. Just giving you something else to check because mine was doing the exact same thing. good luck
James

That's nice to know . I am going through the same thing with my '78 85hp evinrude. I have been assuming that the power pack is bad on the one side also sense I lost spark to the one side.

I would much rather buy a $60 power pack then a $300 (if not more) stator.

 

[brandon.prewitt]

Re: No spark on the left two cylinders.

How do you check a power pack, and what does it cost?

Expensive, huh.

 

[iwombat]

Re: No spark on the left two cylinders.

Brandon, check the forum for "runaway engine" if you don't believe me. You don't want to go over 2k for even an instant. Your motor can runaway and seize. No kidding.


A good description here: http://forums.iboats.com/showthread.php?t=194958

 

[OBJ]

Re: No spark on the left two cylinders.

Brandon....I also have an 86' 90 horse. What you want to do is swap the power packs....from one side to the other and see if the cylinders that were not firing, now fire. If they do, bad pack, replace it. If they do not fire after swapping sides, then likely the timer base is bad. But I would say right off, it's the pack.

Let us know what ya' find.​

 

[brandon.prewitt]

Re: No spark on the left two cylinders.

Dang I shoulda thought of that.

 

[brandon.prewitt]

Re: No spark on the left two cylinders.

Runaway.

I've never heard of that before runnin on muffs.

I guess it's better to use a trash can?

 

[jbjennings]

Re: No spark on the left two cylinders.

Brandon,
I don't think it will help to use a trash can. They just aren't designed to run high rpms with no load, even if you don't have one of those thermal runaways.
You could snag a piston skirt and chip it or many other things. (From what I've learned while eavesdropping on other folks threads).
Just a helpful idea,
Hope you get it fixed, JBJ

 

[tashasdaddy]

Re: No spark on the left two cylinders.

keep reving it and you will see what a connecting rod looks like. hopefully it will not hit you.

 

[ezeke]

Re: No spark on the left two cylinders.

The runaway engine is caused by fuel burning when there is no spark. Once it starts, you cannot stop it except by running out of fuel. It almost never happens in gear when running, but happens too often in neutral regardless of the other circumstances. It is most likely to happen in a motor with carbon deposits because you need something glowing hot enough to keep igniting the fuel.

You need to do a compression test and a spark test. Both should be run with all spark plugs removed, by the numbers.

 

[iwombat]

Re: No spark on the left two cylinders.

We're just trying to save you from toasting a powerhead, or worse - personal injury.

Thermal runaway is a pretty scary event.

 

[brandon.prewitt]

Re: No spark on the left two cylinders.

Thanx for the help diagnosing the problem, and the tip on the runaway.

I swapped the power packs and the no spark traded sides.

I tried to run to the boat parts stores in town but they are both closed.

I'll get it tomorrow and let you know what happens.

 

[brandon.prewitt]

Re: No spark on the left two cylinders.

It ran great but man it sure drinks down some fuel. Once the 6 gallons tank was empty I switched over to the 30 gallon built in. Ran fine for about 3 gallons until it started to slow down. I guess I picked up some trash.

It only ran 33 miles per hour when I clocked it with my GPS(speedo no workie) I expected more, any ideas? I'm guessing the prop.

Any ideas how to clean out the tank without removing it? I siphoned 9 gallons out before I ran it. I left maybe two gallons but I couldn't get them out.

 

[crb478]

Re: No spark on the left two cylinders.

It ran great but man it sure drinks down some fuel. Once the 6 gallons tank was empty I switched over to the 30 gallon built in. Ran fine for about 3 gallons until it started to slow down. I guess I picked up some trash.

It only ran 33 miles per hour when I clocked it with my GPS(speedo no workie) I expected more, any ideas? I'm guessing the prop.

Any ideas how to clean out the tank without removing it? I siphoned 9 gallons out before I ran it. I left maybe two gallons but I couldn't get them out.

How many RPM's are you turning with your prop at WOT? If the boat is on a trailer you may need to really tilt the trailer us to get the fuel to where it can be siphoned out. Just a little bit of crud can ruin your day.