Next hotter plug from QL77JC4?

[CaneCutter79]

My motor runs cold even during the summer months even on a brand new set of plugs my last outing. Per my repair manual, it?s one of the possible causes of an ongoing issue. My thermos are new and recently replaced but motor is very cold.

I want to try the next hotter plug to raise the temp a little and see if that helps. What do I try? I am currently using Champion QL77JC4 and Evinrude recommends UL77V (equivalent of QL77JC4).


My motor info is in my signature.

 

[CaneCutter79]

Re: Next hotter plug from QL77JC6?

Re: Next hotter plug from QL77JC6?

I should mention that my current new plugs are gapped at .33

 

[Chinewalker]

Re: Next hotter plug from QL77JC4?

I would be looking for other causes before messing with plug heats. You mentioned new thermostats - did you check the bypass valves while you were in there? Are the diverters in the cylinder block in place and in good shape - these are small pieces of what looks like hose that get the water to flow a distinct path through the block, visible when you pull the cylinder heads.

 

[F_R]

Re: Next hotter plug from QL77JC4?

No matter what plug you put in there it will not affect the engine temperature. "Hot" or "Cold" refers to the temp of the spark plug tip, not the engine. Well ok, I admit, if the plugs were hot to the extreme, it may cause preignition, which will affect the engine temp, but destroy it at the same time.

BTW, "reading" the plugs by appearance went out the window with the advent of CDI ignition. Expect them to look like crap after prolonged idling. That's ok, the ignition is able to fire through the crap.

EDIT: I believe UL77V is a surface gap plug. They are cold to the extreme. In fact, they don't heat up at all.

 

[CaneCutter79]

Re: Next hotter plug from QL77JC4?

Motor rebuilt in Feb. I replaced a full thermo kit in March so yes the bypass valves are new and the diverters are new.

 

[CaneCutter79]

Re: Next hotter plug from QL77JC4?

OK.

I'm going to make more detailed checks on the ignition system then. Its getting spark, just runs too much fuel to combustion chamber and is fouling plugs I think. Based on my manual, I was thinking it could need a hotter plug but...........it's not the factory manual. Just another mechanic's opinion I guess.

Motor runs fine cold or warm. After it sits, it has problems running. Idles fine but fast idle has no impact on it and it floods out until you can get the chamber cleared.

It's a fuel metering issue and I'm trying to chase down all possible causes.

 

[Vic.S]

Re: Next hotter plug from QL77JC4?

QL77JC4 are conventional plugs. They should be gapped at 0.030", but 0.033" should no problem as the gap recommended originally was I think 0.040"

UL77V are surface gap plugs and were originally suggested as alternatives for sustained high speed operation

Originally un-suppressed L77J4 plugs were specified ( now obsolete types) L77JC4, or suppressed QL77JC4, are the current alternatives and are the only ones now recommended.


The heat rating of the plugs does not control the running temperature of the engine. It affects the temperature of the plug firing tip .

A plug with a heat rating too low will have a tendency to be come fouled. An excessively hot plug might result in damage to the piston crown.


Fromwhat you say I think you need to look at the carbs.. Floats, and needle valves . It sound as though one, or both carbs is flooding due to the needle valve not seating or a defective or incorrectly adjusted float

If you are sure the engine is running too cool perhaps you should check the installation of the thermostats and pressure relief valves but it might be a good idea to check the actual temperature first

 

[CaneCutter79]

Re: Next hotter plug from QL77JC4?

Fromwhat you say I think you need to look at the carbs.. Floats, and needle valves . It sound as though one, or both carbs is flooding due to the needle valve not seating or a defective or incorrectly adjusted float

If you are sure the engine is running too cool perhaps you should check the installation of the thermostats and pressure relief valves.

Thank you! The water temp is currently 83-84 and I can't get the motor over 135 at idle. It drops less than that when running WOT. Does that seem too cold? Or adequate?

Also, will be checking carbs soon. Going to backcheck the ignition system with detailed readings from my DVA just to be sure. I suspect carbs as well.

 

[Vic.S]

Re: Next hotter plug from QL77JC4?

Thank you! The water temp is currently 83-84 and I can't get the motor over 135 at idle. It drops less than that when running WOT. Does that seem too cold? Or adequate?

Also, will be checking carbs soon. Going to backcheck the ignition system with detailed readings from my DVA just to be sure. I suspect carbs as well.

I dont know exactly what the temperature of your engine should be. 135?F at idle may be a little low but probably within spec. You'd have to check with the manual

At high speed the relief valves open so the temperature falls and is no longer controlled by the thermostats.

If your engine is firing properly on all cylinders there is not likely to be much wrong with the ignition.

If the carbs are flooding sort that out.

Plug types, ignition faults and temperature issues I feel may well be red herrings

 

[Joe Reeves]

Re: Next hotter plug from QL77JC4?

1979 85hp Evinrude, rebuilt February 2013, running temperature is 135 degrees................

The thermostats open at approximately 143 degrees so normally the engine would be running somewhat hotter than that.

Water deflectors, if not installed properly or if swelled, would result in overheating, not a cold running engine.

The fact that your engine is running colder than the temperature of which the two thermostats are rated indicates that something is amiss within the thermostat/water bypass housing.

I'd suggest that you stop looking elsewhere and double check the thermostats and bypass valve assemblies.

 

[Fleetwin]

Re: Next hotter plug from QL77JC4?

I dont know exactly what the temperature of your engine should be. 135?F at idle may be a little low but probably within spec. You'd have to check with the manual

At high speed the relief valves open so the temperature falls and is no longer controlled by the thermostats.

If your engine is firing properly on all cylinders there is not likely to be much wrong with the ignition.

If the carbs are flooding sort that out.

Plug types, ignition faults and temperature issues I feel may well be red herrings

135*F is pretty much what you are going to see on a Crossflow V-4.

If you idle a lot, you can jump the plug gap up to about .038". It helps with idle smoothness.

The others are correct, spark plug temp. rating has nothing to do with engine operating temp.

Stick with what you have and avoid the "surface gap" plugs if you idle a lot. Increase the gap and see what happens.

All my Crossflows liked a wider gap and use Champion plugs ONLY.

 

[CaneCutter79]

Re: Next hotter plug from QL77JC4?

135*F is pretty much what you are going to see on a Crossflow V-4.

If you idle a lot, you can jump the plug gap up to about .038". It helps with idle smoothness.

The others are correct, spark plug temp. rating has nothing to do with engine operating temp.

Stick with what you have and avoid the "surface gap" plugs if you idle a lot. Increase the gap and see what happens.

All my Crossflows liked a wider gap and use Champion plugs ONLY.

Cool tip. Thanks! Will definitely try. I troll a lot (fishing) and I'm pretty much right at idle. Oddly enough, my motor doesn't have a problem here. Only when I try to load it on the trailer. If I park the boat to back my trailer it, it will crank but if I put it in gear it dies.


I am really thinking the boat just doesn't want to get out of the water! That's really about the time I have problems! LOL!

 

[Fleetwin]

Re: Next hotter plug from QL77JC4?

Cool tip. Thanks! Will definitely try. I troll a lot (fishing) and I'm pretty much right at idle. Oddly enough, my motor doesn't have a problem here. Only when I try to load it on the trailer. If I park the boat to back my trailer it, it will crank but if I put it in gear it dies.


I am really thinking the boat just doesn't want to get out of the water! That's really about the time I have problems! LOL!

Cane Cutter.

Stalling is a different issue. That leads to Sync/link and carb issues.

That engine should never stall on accel. They run rich enough to avoid that. If it does, you're leaning out somewhere.

 

[Joe Reeves]

Re: Next hotter plug from QL77JC4?

Sometimes I wonder why I bother.

 

[CaneCutter79]

Re: Next hotter plug from QL77JC4?

Sometimes I wonder why I bother.

I haven't ignored you Joe. I'm going to check the thermo assembly just to make sure everything is good. I put in a full replacement kit in March and the issue was occurring before I replaced the thermos. That fix didn't solve the problem. I'm pretty sure its carb related but I still need to eliminate the ignition system for any weak spark issues after it warms up. It had a weak bank during the rebuild so I replaced the stator/rectifier. That helped but didn't totally solve the issue.

Thank you for your help Joe. I appreciate it.

 

[seahorse5]

Re: Next hotter plug from QL77JC4?

The next warmer plug is a QL82C but as the others mentioned, plug fouling is normally due to other engine factors than the plugs themselves.

 

[CaneCutter79]

Re: Next hotter plug from QL77JC4?

135*F is pretty much what you are going to see on a Crossflow V-4.

If you idle a lot, you can jump the plug gap up to about .038". It helps with idle smoothness.

The others are correct, spark plug temp. rating has nothing to do with engine operating temp.

Stick with what you have and avoid the "surface gap" plugs if you idle a lot. Increase the gap and see what happens.

All my Crossflows liked a wider gap and use Champion plugs ONLY.

Your tip seemed to work. Thanks! I can now idle in gear at 400-500rpm and it's as smooth as melting butter! The motor has never idled this smoothly or that low before without strain or sounding as if it was starting to lean out.

I had a lync/sync issue where the timer base was not advancing due to "gummy grease" that cause it to bind and not engage forward freely when the throttle lever was engaged. THIS was the sole problem with my motor for weeks and I didn't know it wasn't normal until I finally checked the lync/sync again and played with the timer base lever and could feel the friction. I knew it wasn't normal, then realized why advancing the timing was important and finally.........my head popped out of my behind and the light shown around me. LOL!

Joe.....
I'm going to check the thermo housing next and see if the bypass valve assembly is good. Just to make sure everything is ok.

So far, the motor is running extremely well since I gapped the plugs to .38 and fixed the timer base. I had to completely remove the timer base assembly and clean off the "gunk" that had built up. I replaced it with 3-N-1 oil designed for electric motors and it's as smooth as it can be now. The lighter weight oil should last a long time.

 

[CaneCutter79]

Re: Next hotter plug from QL77JC4?

1979 85hp Evinrude, rebuilt February 2013, running temperature is 135 degrees................

The thermostats open at approximately 143 degrees so normally the engine would be running somewhat hotter than that.

Water deflectors, if not installed properly or if swelled, would result in overheating, not a cold running engine.

The fact that your engine is running colder than the temperature of which the two thermostats are rated indicates that something is amiss within the thermostat/water bypass housing.

I'd suggest that you stop looking elsewhere and double check the thermostats and bypass valve assemblies.

OK, Joe. I've gotten a chance to take the thermo housing out (REALLY big pain in the rear as I cannot get the lower cowling to lower, it has to be lifted after removing the powerhead....I tried, won't drop down, must be lifted out).

The bypass valves match the manual's installation instructions and I re-tested the new thermos. They open around 150......not 143 which is a bit of surprise. They are only a few months old. PLUS........this would cause the motor to run warm, not cold.

So now what.........???? Where else do I look?

 

[oldandintheway]

Re: Next hotter plug from QL77JC4?

Why don't you use the recommended plug - UL77V ? No gap issues. Just a thought.

 

[CaneCutter79]

Re: Next hotter plug from QL77JC4?

Here is a video of me testing the motor after removing the thermostat assembly and checking the bypass valves as well as the thermostats.

The motor has been cold since yesterday and I've run the motor about 5mins to get it this warm. The bypass valve on the left opens first. Right one is closed. Odd......
So I rev up the motor a bit at fast idle and it opens right up. Great flow of water coming out. This tells me it's DEFINATELY the bypass valves opening before the thermostats open. Water is flowing out of the motor rather warm to touch but definately not 140-150 degrees. When it's on plane, the water flows out even more and my temp gauge drops like you tied a weight on it.

So motor is cold because bypass valves are opening. Valves, stats, springs, gaskets, etc are less than 6mo old. It's been doing this since.

Is this normal??


Here's the vid. I'm pointing my laser temp gauge at the sparkplugs since it gives me the hottest temp per cylinder. Tried the heads but it drops a few degrees so readings at plugs are a fair indication of temp.

https://www.youtube.com/watch?v=iI25w72sV-4&feature=youtube_gdata_player