OMC 2.3 Cobra Melted Spark Plugs, Resolved and Fixed

[Bulbash]

Yesterday we went out and spent most of the day playing with wake board, boat runned well until the end of a day few minor misfires almost not noticeable. Today I went out to the lake , but runned the boat maybe an hour... On the way down boat was misfiring really badly, engine died three times before we got to marina. Got home, pulled spark plugs, #3 & #4 cylinders, spark plugs tips are melted down completely. Spark plugs are Champion 8071 I installed them this May and they are marine spark plugs that are recommended for my engine.

Checked compression it is 165, 165, 170, 160.
What would cause something like that, should I install another set of new plugs or...?

 

[Bondo]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Yesterday we went out and spent most of the day playing with wake board, boat runned well until the end of a day few minor misfires almost not noticeable. Today I went out to the lake , but runned the boat maybe an hour... On the way down boat was misfiring really badly, engine died three times before we got to marina. Got home, pulled spark plugs, #3 & #4 cylinders, spark plugs tips are melted down completely. Spark plugs are Champion 8071 I installed them this May and they are marine spark plugs that are recommended for my engine.

Checked compression it is 165, 165, 170, 160.
What would cause something like that, should I install another set of new plugs or...?

View attachment 208513View attachment 208512View attachment 208511View attachment 208510

Ayuh,.... That's Detonation,... Might be Lean, or outa time,...

 

[Bulbash]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Ayuh,.... That's Detonation,... Might be Lean, or outa time,...

Also, yesterday I installed a new prop one pitch higher, but rpms been slightly under 5000rpm instead of 5400 - 5600 at WOT as recommended...

 

[Bulbash]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Any ideas guys?

 

[Bondo]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Any ideas guys?

Ayuh,... Go back to a smaller prop,... The larger prop is causin' the motor to lug,...

Check the Timing,....

Check the Fuel Flow,...

 

[Bulbash]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Just realized that spark plugs that were in the engine were not correct ones, instead of Champions RS12YC I had RC12YC, everything is the same, but the reach is 1mm longer on the ones that I had in the engine when it detonated. Would 1mm longer plugs cause a detonation?

 

[Silvertip]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

We can speculate all day but the wrong plugs can cause issues. As can timing. As can lean carburetion. As can overheating. As can lugging the engine with an incorrect prop. You need to investigate each of those characteristics.

 

[Bulbash]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

ok, so today I replaced all the spark plugs with the new correct ones, put the 15pitch prop back, replaced impeller and thermostat. Runs very well on muffs, but the real test will be tomorrow when I get on the lake...

As for timing and carb settings I had it adjusted back in May by a mechanic and boat runned fantastic all summer, so I assume those settings would not change by itself... Right?

 

[Speak]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Bullbash all good support and feedback from the crew here. I would lean towards preignition. Have u checked just to be sure if the distributor has loosened off a bit. Sure looks like to much timing advance. Check inside the distributor that the mechanical advance is not sticking or stuck. I would think if you have a lean situation that the boat would sputter under hard acceleration( starving). Put some new plugs in her run it set the ignition timing then run it under a variety of loads and speeds taking notes of the performance. Then pull those pluhs and see what they look like. That's what I would do. Might just have been those wrong plugs u installed. Let us know.
Stuart

 

[Bulbash]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Checked the distributor, all seems fine, no movement all screws are tight... So I would doubt that the issue came from there...

Timing is a different story, I never done it myself, but I'm looking into getting a timing light and see if I can figure it out tomorrow...

 

[Speak]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Checking the timing is very easy on that motor bulbash. Let me if you have any specific questions. Call me if you need. I think you have my number.

Cheers
Stu

 

[Bulbash]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Went out to the lake today... Boat runned very well, however I noticed that temperature gauge fluctuates between 175 and 225... It seems that at low rpms there is not enough water being pumped... as soon as I throttle up temperature goes down.

When got back checked riser, it seems clear, not much rust, flapper works well impeller and housing is new, thermostat is new what else can cause higher temperatures???... The only deficiency I noticed was when running on muffs there is a very minor leak from under the impeller housing...

Tomorrow will be getting a timing light to see if timing is correct...

 

[Speak]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Should be no leaks at that housing. This will cause issues. Replace or re seal that housing and re test in the lake.

 

[Bulbash]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Should be no leaks at that housing. This will cause issues. Replace or re seal that housing and re test in the lake.

I used liquid gasket to seal the housing in place... Now need to get on the lake to see how it will perform...

 

[Bulbash]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Another symptom I noticed that when I noticed that engine is not running the way it should; after running for some time you shut off engine and instead of just shutting off it sputters for a second or two and then it shuts off... Now when I got the correct spark plugs it still keep doing it. To me it sounds like temperature inside of the engine is so high that the fuel is keep igniting just from the temperature of the engine itself.

I will be checking my timing today, and report back.

Also, is there anyway to check if the engine is running lean? It does run very smooth at idle when warm, minor vibration while cold...

 

[Levinz11]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

Went out to the lake today... Boat runned very well, however I noticed that temperature gauge fluctuates between 175 and 225... It seems that at low rpms there is not enough water being pumped... as soon as I throttle up temperature goes down.

When got back checked riser, it seems clear, not much rust, flapper works well impeller and housing is new, thermostat is new what else can cause higher temperatures???... The only deficiency I noticed was when running on muffs there is a very minor leak from under the impeller housing...

Tomorrow will be getting a timing light to see if timing is correct...

That is an issue. It's probably sucking air when on plane and not supplying enough water to the thermostat housing. When at idle the water level is above the housing and no air is entering the system making the temps return to normal. Check that housing gasket, it can be a bugger to get it to seat correctly.

The higher temps are causing your dieseling issue most likely. That or your timing is retarded too much.

 

[Bulbash]

Re: OMC 2.3 Cobra Melted Spark Plugs, Need HELP

Re: OMC 2.3 Cobra Melted Spark Plugs, Need HELP

Check that housing gasket, it can be a bugger to get it to seat correctly

I does make sense that all issues could be coming from that gasket. Just to be clear, when setting impeller housing, gray paper gasket goes first, then metal, then housing with o-ring? or metal gasket first?

 

[Speak]

Re: OMC 2.3 Cobra Melted Spark Plugs

Re: OMC 2.3 Cobra Melted Spark Plugs

I think to much advance caused run on not retarded timing. Could be wrong thou.

 

[Bulbash]

Re: OMC 2.3 Cobra Melted Spark Plugs, Need HELP

Re: OMC 2.3 Cobra Melted Spark Plugs, Need HELP

ok got some time today to check timing, aligned camshaft to the proper mark (as per manual) bottom pulley marking which had to point to zero is pointing slightly off... Would that be a problem?

 

[nedc]

Re: OMC 2.3 Cobra Melted Spark Plugs, Problem Found

Re: OMC 2.3 Cobra Melted Spark Plugs, Problem Found

i just went thru the timing setup on my newly rebuilt 2.3. Unless that angle of the photo is making it look worse than it is, it looks like the the timing is off one tooth. That crank pulley should be dead on the TC mark when the cam is on it's mark.