1980 115 johnson no power, low RPM

[wiancko]

First time boat owner, but several years mechanical experience on four stroke, natural gas and diesel engines.

I am stumped,..... I have a fairly clean 1980, 115 johnson engine that couldn't pull very well. spec'd out the correct prop, installed new plugs (Champion). Was able to get engine running better, but still not able to pull a single skier (which I would like to be able to).

Ran the boat for approx. 3 - 4 hours, descided to verify plug condition, found 3 out of 4 firing, one looked like brand new. Troubleshoot ignition issue and found the module was not working properly, installed an OEM model and then my engine went severly down hill.

Was it coincidence that now I do have spark on all holes, but have very minimal horsepower and RPM's. I went and tested all coils, spark test at 1/2", compression at 125psi, timing does advance, water coming out visual tube (which tells me waterpump is working), changed out the needle and seats in both carbs. However,.... I also tried load testing in the water with the front off the carbs and sprayed a mist of fuel with no change in RPM either, also maually open throttle plates to eliminate throttle control issues, still nothing. I felt the heads and found one bank quite cooler than the other head which I thought was strange, failed thermostat?

My question is, if I do not have proper cooling, could this cause the engine to go into limp mode? (keep in mind this is a 1980 motor) I have checked spark several times and have determind that spark is there, never did verify though under a load condition. I am going to check the stats to verify this is not the issue.

I am dieing here, any ideas at to what to look at?

 

[iwombat]

Re: 1980 115 johnson no power, low RPM

Well, you've checked compression, fuel, and spark. So, let's move on to some other suspects. What do your plugs look like on the cool bank?

 

[emdsapmgr]

Re: 1980 115 johnson no power, low RPM

You've done some good analysis thus far. Solid logic. It's possible that one thermostat is stuck open. That will cause one head to run cool to the touch. While not a good thing in the long run (excess carbon accumulation on that head) it really should not affect your WOT running. Seems like your troubles go back to the ignition part replacement. I am thinking that you may have replaced one of the two power packs (you call it a module) on the engine. (one controls the spark to each head.) That engine is too old to have any limp modes or throttle/spark restrictions. I'd suggest you do a cyl drop test (spark test) while idling on the trailer. Pull one spark plug wire off one of the plugs. (with an insulated set of pliers.) The engine should slow down. Replace the plugwire and go to the next plug. Same thing should happen. If you pull one of the plug wires off and the idle does not slow,-it's not firing. Since the two power packs are identical, you can swap them for spark testing purposes. If your test shows all of them firing, then you have a fuel issue. Your compression at 125 is comparable to when it came out of the factory. It is also possible that the flywheel key has sheared. Usually when this happens, the engine gets so out of time, it won't run. It's possible that the flywheel key is sheared, but the flywheel is still close to original timing. It would run in this case, but would have no power. Check the timing of #1 cyl with the #1 marks on the flywheel.

 

[wiancko]

Re: 1980 115 johnson no power, low RPM

Well, you've checked compression, fuel, and spark. So, let's move on to some other suspects. What do your plugs look like on the cool bank?

the plugs on the cool side do look wet, where as the other bank looks dry.

 

[wiancko]

Re: 1980 115 johnson no power, low RPM

You've done some good analysis thus far. Solid logic. It's possible that one thermostat is stuck open. That will cause one head to run cool to the touch. While not a good thing in the long run (excess carbon accumulation on that head) it really should not affect your WOT running. Seems like your troubles go back to the ignition part replacement. I am thinking that you may have replaced one of the two power packs (you call it a module) on the engine. (one controls the spark to each head.) That engine is too old to have any limp modes or throttle/spark restrictions. I'd suggest you do a cyl drop test (spark test) while idling on the trailer. Pull one spark plug wire off one of the plugs. (with an insulated set of pliers.) The engine should slow down. Replace the plugwire and go to the next plug. Same thing should happen. If you pull one of the plug wires off and the idle does not slow,-it's not firing. Since the two power packs are identical, you can swap them for spark testing purposes. If your test shows all of them firing, then you have a fuel issue. Your compression at 125 is comparable to when it came out of the factory. It is also possible that the flywheel key has sheared. Usually when this happens, the engine gets so out of time, it won't run. It's possible that the flywheel key is sheared, but the flywheel is still close to original timing. It would run in this case, but would have no power. Check the timing of #1 cyl with the #1 marks on the flywheel.

Can this test be done with a set of muffs on the leg? I do have a water tub that I plan to set the leg into and simulate running in the water.

I just removed and tested the stats, both seem to be opening okay, look rather well used. I would like to change them out as I have them out now. So there is no De-rate on this year? okay, so much for that idea.

I did test the advance while I had it running and the timing does advance. How much can it advance? at idle, no load I believe I was roughly around 5 degrees , should be approx. 28, correct? That's what the label states.

Shearing a key? is this common? I had it happen once on my lawn mower. Seems rare, but feasible. If I remove the retainer nut, I should be able to see, correct?

(by the way, really appreciate your help on this challenge of mine.)

 

[iwombat]

Re: 1980 115 johnson no power, low RPM

Wet, as in fuel wet, or water wet. Do they look steam cleaned?

 

[emdsapmgr]

Re: 1980 115 johnson no power, low RPM

If you run the engine in a tub of water, you'll have to let the garden hose run constantly into the tub. The exhaust will heat that tub quickly, so keep cool water running through it. Doubt you'd have water intrusion into the cyl if the compression is 125 all holes. The fact that the plugs look so different between heads is significant. One side may not be firing.

 

[wiancko]

Re: 1980 115 johnson no power, low RPM

If i have spark, during a plug test, shouldn't i have spark in the chamber as well? Unless the compression kills my spark? I have seen a spark in the open atmoshere but not in the chamber due to compression compiling the molecules and the coil not able to give a good enough spark. Is this possible in a marine application?

I will have to try and set up the tub shortly and perform a running test.

 

[wiancko]

Re: 1980 115 johnson no power, low RPM

It looks like fuel, I ran the boat engine with the air manifold off and spray a mist of fuel into the chamber with no increase in fuel and the plates were wide open with ample fuel coming out of tubes inside carb.

 

[iwombat]

Re: 1980 115 johnson no power, low RPM

It's possible to get water intrusion from a blown exhaust gasket. This would give you good compression readings, and water in the cylinders. That doesn't sound like the case here given what you're seeing on the plugs, but it was worthwhile to check it out. The open-air spark check is for simulating what the coils must do under load. So, yes they should be firing in the cylinders. Have you tried swapping plugs and/or wires from one side to the other? It's also probably time to put an inductive timing light on the plug wires of that bad bank to see if they really aren't firing.

 

[emdsapmgr]

Re: 1980 115 johnson no power, low RPM

When you said 3 of 4 plugs were firing, which plug did not appear to fire? Top or bottom cyl, which side?

 

[wiancko]

Re: 1980 115 johnson no power, low RPM

Well, i worked on my boat last nite till late and found out that nothing is quite what it appears...... i pull the leads off while running and found left bank dead, swapped power packs, no difference. swapped coils back and forth several times as the spark was disappearing and reappearing randomly with the unit running with muffs on. Very confusing. Finally i put the coils on where they originally were and all of a sundden the engine purred like a kitten. Go figure. I guess a new set of coils will be installed.

Does this sound familiar to anyone?

Thanks for everyones input and help. I will keep you posted on the results as i am taking it out this week for a test run.

 

[Daviet]

Re: 1980 115 johnson no power, low RPM

Sounds like bad grounds on the coils. Make sure the ground connections are clean and tight, maybe install some star washers on the ground wires.

 

[iwombat]

Re: 1980 115 johnson no power, low RPM

Coils are usually either good or totally gone. Intermittent coil operation points to bad connection or some other component. Daviet has it right. Sand/file down the ground connections, put on some good stainless star washers, and i'll bet this clears up.