Thermostat bad or weak stator fouling plugs?

[CaneCutter79]

During my rebuild, the stator readings were low on the left side of the motor. I was told they are within spec but on the weaker end.

I have a new starter and I'm about 3-4hrs into my 10hr break-in using double oil. The old plugs are still in use and I'm going to get new at the end of break in.

After 2.5hrs of run time, the motor didn't want to start. No fire. I choked it with the manual choke switch and it finally started after being flooded. I removed the plugs, cleaned them in Sea Foam and put them back in. Motor started great again. Next trip out, motor starts great after its warmed up. After an hour of run time.....back to fouled plugs I think. They are coated with carbon and oil.


So is this common for double oil and break in? Should I get new plugs now and after break in?

Or could this be the stator? I'm thinking fouled plugs and not stator. Sometimes when its hard to start, it finally fires enough to start and its sluggish. Then it revs up with the throttle open as normal and smooths out. As if it burned the carbon off the plugs.

Thoughts?

 

[CaneCutter79]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

I should mention that after its started and running, it restarts easily if you kill the motor and restart immediately. Starts easily. Let it sit for 15mins and its sluggish again.

The carbs were completely rebuilt in the rebuild by the way.

 

[CaneCutter79]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

Any input on this one?

 

[seahorse5]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

Are you using the recommended Champion QL82C plugs ?

Are the thermostats allowing the engine to idle about 140?F on the top of each cylinderhead?

Are the recirculation hoses, valves and fittings open and operational?

 

[CaneCutter79]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

I have QL77JC4. My mechanic confirmed I need the 77JC4 plugs. They are last seasons plugs and the motor was just rebuilt. Rather than put new plugs in for 10hrs only to replace later, he said run the old ones and then replace them.

Yes all hoses are operational. As for 140 temp, I don't know. I have a new temp gauge and it hasn't registered any heat yet. When the motor is running and warm, the heads and blocked are warm to the touch but not so warm I can't hold my hand on it. Almost too cool even. I was told it should run about 140 but it doesn't seem to be that warm.

How can I check? Laser temp gauge?

 

[boobie]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

Yes, a laser temp gauge. That way you'll know exactly what temp it is running. If you can hold your knuckles on top of each cyl for over 5 seconds at idle it's running to cold.

 

[CaneCutter79]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

If you can hold your knuckles on top of each cyl for over 5 seconds at idle it's running to cold.

I'm betting I can. If it's "too cold", what's the solution? Is it the weak readings on the stator not creating enough current? I was told the stator creates the current, the packs distribute the power to the coils and the coils to the plugs. Or something like that. Also, the packs and coils checked out fine when my mechanic checked them less than a month ago during the rebuild. His only concern was that the stator will eventually get worse and become below spec as it is currently on the low end of the required min. current.

 

[boobie]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

The theromostats control the mtr temp. They have nothing to do with the ignition system. Have you checked your spark with an open air gap spark tester set at 7/16 " when the prob occurs ?? This may tell you something.

 

[trendsetter240]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

During my rebuild, the stator readings were low on the left side of the motor. I was told they are within spec but on the weaker end.

I have a new starter and I'm about 3-4hrs into my 10hr break-in using double oil. The old plugs are still in use and I'm going to get new at the end of break in.

After 2.5hrs of run time, the motor didn't want to start. No fire. I choked it with the manual choke switch and it finally started after being flooded. I removed the plugs, cleaned them in Sea Foam and put them back in. Motor started great again. Next trip out, motor starts great after its warmed up. After an hour of run time.....back to fouled plugs I think. They are coated with carbon and oil.


So is this common for double oil and break in? Should I get new plugs now and after break in?

Or could this be the stator? I'm thinking fouled plugs and not stator. Sometimes when its hard to start, it finally fires enough to start and its sluggish. Then it revs up with the throttle open as normal and smooths out. As if it burned the carbon off the plugs.

Thoughts?

Yes, plugs foul easily when you are running 25:1. Try not to let it idle for extended periods while you are running the double oil. Just 1-2 minutes at first warm up then go. I'm dealing with the same thing right now; 3-4 hours into break in and plugs fouled after idling around for 15 minutes killing time on the water.

My plugs are QL8YC and my motor is a 96 115hp.

 

[trendsetter240]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

Also, yes get new plugs at the 20 hours mark and re-torque the head bolts at the same time.

 

[CaneCutter79]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

No, I haven't checked the spark with an open air gap spark tester. I have one. I'll do this next time I'm out and see what happens. What should I look for? (other than a good spark!) If low spark, then it could be the stator or something in the ignition system. If I get good spark, then it's not ignition and something else correct?

My manual gives me instructions on testing the thermostats so I think I can do that. I really don't want to take the heads off to check the temp switches. I have a 15mo warranty on the rebuild. My mechanic is 4hrs away and I really don't want to haul it 4hrs away unless I have to. Hopefully the termostat tests will tell me something.

So from what my manual reads, a motor running too cold will not allow the heated water to pass thru the discharge and as engine speed is increased, the water pump pressure opens the relief valves. This bypasses the thermostats and allows the motor to run cooler at higher engine speeds. Do I have that right?

 

[CaneCutter79]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

I found an old thread from iboats where a gentleman had the same issue I have. Motor is cold natured and you have to manually choke the motor to start on initial start with fast idle. Once started, runs great. Stop motor, restart within 5-10mins and starts fine. After 15-30mins, you have to manually choke the motor again.

From what I read in this older thread, I have either a carb issue or a thermostat issue. I feel like I'm getting somewhere now.
http://forums.iboats.com/johnson-evinrude-outboards/evinrude-90hp-vro-86-dramas-please-help-me-461153.html

Now my issue differs because I just had the carbs completely rebuilt by my mechanic. I seriously doubt he has something incorrect as he's been rebuilding carbs for 25yrs plus and is a teacher at a marine repair school. So this leads me to thinking testing the thermostats is a good start. If the thermostats test OK, I'll call my mechanic and ask him to take a look at the carb settings.

Since I'm in 3hrs on a break-in.............I DO NOT WANT EXCESSIVE CARBON BUILDUP AROUND THE RINGS! I want to get this fixed and I want to finish breaking in the motor correctly with it running as it should........allowing warm water to bypass and run cooler at higher engine speeds.


Does anyone disagree with my assessment on where I think the issue lies? It really sounds like it could be the thermostats. Is that not part of a rebuild? I'll ask my mechanic if he remembers checking them.

 

[phillnjack2]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

If i was getting an engine rebuilt i would expect it to have new thermostats definitely.
Any of the consumables that come out get binned and new ones put in,this is not just a rebuild thing its a normal
service procedure anyway.

How long do you have the engine running for when it does start ?
and how fast do you run the engine /what rpms .
does water come out of the exhaust holes at top of the leg ?
Is this in a water butt or off the mains on muffs ?
if its on muffs and you have a huge amount of pressure then turn it down a touch, better yet run in water butt.



phill

 

[CaneCutter79]

Re: Fouling plugs or weak stator?

Re: Fouling plugs or weak stator?

If i was getting an engine rebuilt i would expect it to have new thermostats definitely.
Any of the consumables that come out get binned and new ones put in,this is not just a rebuild thing its a normal
service procedure anyway.

How long do you have the engine running for when it does start ? About 1min to warm up. Then I leave the ramp/dock and run maybe 10-20mins to a fishing spot. May fish one area for up to 20-30mins or more and then I get a cold start again
and how fast do you run the engine /what rpms . See answer below. Varies due to break in. Around 4,000.
does water come out of the exhaust holes at top of the leg ? Yes. Water is coming out
Is this in a water butt or off the mains on muffs ? Yes, in water and not on muffs
if its on muffs and you have a huge amount of pressure then turn it down a touch, better yet run in water butt. What amount of pressure? You mean the water pressure on the hose? I think that's what you're referencing. I have not tested the cold start issue on the hose so that's not an issue for me. All of my issues have been "on water".

phill

The mechanic said both sides of the engine were running the same temp so he didn't service the thermostats. I typically have to manual (full choke) the engine on cold starts. Then I let it idle for 1 minute and then I take off. Since I'm still breaking in the motor, I try to keep the RMPs around 4,000 or less and now that I'm up to 3hrs on the break in, I occasionally run fullt WOT but no more than 1min at each interval.

I do not "troll" or idle around. It's either running 3,500-4,00 k or it's at WOT. This issue has been going on since before the rebuild so it's an existing issue. My mechanic is convenced it's a weak spartk causing the cold starts.



Can someone deeply explain how a termostat keeps the engine warm? I know the thermo opens when it gets to 140-145 degrees. It allows the warm water to escape so the engine can run cooler at higher RMP. So how do you get warmer water to stay in and warm the engine? Is it because the thermo is stuck open?

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

So after reading and searching the forum for similar issues, I feel I may have a series of issues that's creating my issue.

- Stator has a weaker spark on left side of motor, within spec but low.
- Motor is running too cold and in combination with double oil, the plugs are fouling after running the motor up to 1hr
- Motor is running too cold and not reaching 140 degrees and thermostats are not opening
- Floats in carb could have incorrect settings which could cause the flooding issue due to cold motor and fouled plugs with excess carbon


I'm not sure why the carbs would not be correct considering the carbs were just rebuilt by a 25yr+ professional. Could happen but not as likely. It's not good to run the motor too cold because carbon will continue building up around the rings and will eventually cause ring failure and I'm back to rebuilding again. NOT going through that again..........I want to get the motor fixed for long term use and reliable starts.

SO HOW DO I GET THE MOTOR TO STOP RUNNING TOO COLD?

 

[emdsapmgr]

Re: Thermostat bad or weak stator fouling plugs?

I'm suprised you have not checked the cyl head temps with a laser temp gun. You can rent one at most any automotive parts shop. You really need to know if the cyl heads heat up to around 143-145 when at idle. Maybe up to 150-155 when idling in a warm summer lake. That's normal. When you plane the boat out (or rev the engine at the dock), the increased water pressure forces extra cooling water through the block thru the thermostat pressure relief valves. Once on plane and these valves open, the cyl head temps will dive perhaps 20 degrees (or more in a cold lake.) That's also normal. Weak ignition components tend to have problems when the engine heats up to normal operating temps. I'd check the stator voltage output once the engine heats up. I like to test the stator for cranking voltage output, usually 150 volts minimum, as measured with a "peak-reading" voltmeter. You may be able to verify that output votage spec for your 79 on this website: cdielectronics.com. Also, you may be able to detect something with an inductive timing light. Once warmed up and idling, check the spark on each plugwire. The flashes from the timing light should show/detect weak firing, intermittent firing, no fire situations.

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

I haven't had a chance to test the motor yet since my original post. I plan on checking the head temps today. I don't know if I have a "peak-reading" voltmeter. I have a typical digital voltmeter. Not the same thing I guess. I'll google peak voltmeter.

So hearing weak spark once engine is warm is first I've heard of this. Seems to make sense. I'll definately do what I can to check. Any help or detailed instructions I can get on that would be great. I'll look in my manual and see if there are instructions in there as well. I'll let you know the readings once I get them.

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

Yep, I need a DVA adapter for my multimeter to convert it to a peak reading voltmeter.

 

[Chris1956]

Re: Thermostat bad or weak stator fouling plugs?

My old Johnnyrude ran 24::1, had point mgneto ignition(not CDI like you) and I never fouled a spark plug. Double oil is therefore likely not the issue. I would suspect an ign issue or flooding carbs....

 

[CaneCutter79]

Re: Thermostat bad or weak stator fouling plugs?

OK here are some preliminary results. I will test more tomorrow.

Spark test: good spark cold at 7/16" gap. Looks like a stun gun.

Compression (because I am curious) 100psi on both right-hand cylinders, 116psi on top left and 120 on the newly re-sleeved cylinder on bottom left

I've let my mechanic know about compression. I have 3hrs on the break in. I have a 15mo warranty so I'm not worried about compression differences yet.

I have not checked temp yet but will tomorrow. I'll report back. By the way, it started really easy cold today by simply pushing in the key and not manual choke switch. That's a first.