F90TLRB Fouling Plugs 1 &2

[Nowisthetime]

Here are pictures of the plugs... Both pictures show the same set of plugs. When the carbs were removed last fall, the float bowls and the throats were all clean with no hint of dirt. As mentioned this engine has never been run with ethanol fuel. Always used non-ethanol fuel so it is not related to known issues with ethanol fuel. Also float bowls are drained every year before storage.

[99yam40]

very likely both carbs are nasty. do a leakdown test to insure it can mechanicaly seal the do the carbs.
if the enrichment device faikls in the open position it runs two cylinders rich. the can be tested as per the SM for needle extension.

interesting, not sure how it only affects 2 cylinders.
care to enlighten us Rodbolt?

looking at the plugs, 3 &4 look like they are not even firing/burning anything,
too clean

OP how long have those plugs been run when you pulled them?

[Nowisthetime]

The plugs in the pictures were in motor for perhaps 1 month, then the motor when into winter storage (carbs drained, oil changed, etc). Removed plugs this spring. Plugs 3 & 4 do have small amount of ash, browning.

[99yam40]

one month could mean no hours of run time or many.. how many hours was it run, what were the conditions, and how hard?

plugs I have seen running in a well motor have a tan look to the white porcine around the electrode

Rod has already said the enrichment system can affect 2 cylinders causing them to run too rich.
So I would head in that direction. he does this stuff for a living

[rodbolt17]

enrichment for 1&2 are from the upper enrichment valve. 3&4 from the lower.
it is a heated wax pellet design. as it cools a needle retracts.
the next time it is running power is tapped from the lighting coil and heats the wax extending the needle into a seat closing off enrichment.
simple system, easy to check.

[99yam40]

enrichment for 1&2 are from the upper enrichment valve. 3&4 from the lower.
it is a heated wax pellet design. as it cools a needle retracts.
the next time it is running power is tapped from the lighting coil and heats the wax extending the needle into a seat closing off enrichment.
simple system, easy to check.

thanks Rod,
I did not pay attention to more than 1 enrichment valves.

OP time to check the enrichment valve on #1 carb to see why it is not closing

[Nowisthetime]

The enrichment system was my first thought because I knew there were only two and each con*****ed two cylinders. And unlike the two power packs which control cylinders 1 & 3 and 2 & 4, the two enrichers control cylinders 1 &2, and 3&4. So I tried 1.) a new primer starter and when that didn't work, 2.) I tried unpluging/disconnecting the enricher. Obviously the disconnect was going the wrong way. Okay how do "check" if the enricher is working?

[Nowisthetime]

In response to the message about what the 1 month means in hours, I would estimate it is about 15-18 hours. The motor is on a pontoon boat that usually cruises at 2000-2100 rpm for about an hour each day on a 3 day weekend. It is rarely used at wide open throttle. Runs at 4500 rpm when I use the boat to go to a water sample location each week.

Asking Rod how do I test/check to see if the enricher is working correctly?

[99yam40]

service manual has the test procedure for measuring unit cold and then after putting 12 v to it for some time to see if it changes.

But if you have replaced it, then you need to be testing for power on the wire when it is running to make sure it gets there

or check for a bad ground connection

[Nowisthetime]

Okay, so after 3 weeks - sorry for the long delay - here is what I discovered. The voltage from the wiring harness to the enricher was 12.5 +/-. Because the enricher for cylinders 1&2 is further connected to enricher 3&4 I also checked the voltage to that enricher also. Both connections registered at least 12 volts and the ground wires had continuity. Based on the Seloc service manual for Yamaha and Mercury four strokes, the enricher opens as the engine warms up. "Opening" means that a needle value warms up and extends into the enricher body cutting off the additional fuel supply. According to Seloc the enricher when plugged directly to a 12 volt battery for "5" minutes should move up to almost an 1 inch. To see what the results would look like without taking the motor apart, I decided to test the old enricher. Connected it directly to a battery and after the 5 minutes the needle had extended to its maximum. So I took the new enricher off the motor and tried the same test. IT FAILED. Yes a new part didn't work correctly. The enricher head was warm to the touch but didn't extend the needle. I put the old enricher back on the engine but was very CAREFUL to make sure the needle fit into the jet in the bottom of the enricher body. The engine started and after a few minutes was running very smoothly and has been running correctly for the last two weeks. So it would appear to be a defective new part and probably a careless installation of the enricher power head so that the parts were not lined up correctly that caused the fouling of cyliners 1 & 2. Will be removing the plugs in a few weeks after more hours on the plugs to see if the plugs are cleaner and looking normal.

[99yam40]

good to hear it is running well now.

strange things happen sometimes

I take it you measured voltages when the motor was running correct?

[TownsendsFJR1300]

good to hear it is running well now.

strange things happen sometimes

I take it you measured voltages when the motor was running correct?

12.5 volts when testing sounds like the engine wasn't running, the volts would/should have been at least a volt higher(with the engine charging the battery).

Sounds like it's fixed now in any event..

[99yam40]

need to find out where that power comes from to see what you should be reading.

on my old C40 it is ac from the lighting coil and there is nothing there if motor is not running

[Nowisthetime]

The voltage at the enricher was 13.7 or better. Just used 12V to note that the system was getting the voltage necessary for the enricher to work. Have been running the motor now for several weeks and several hours each week and all seems to working as it should