Yamaha 50EJRW 2 stroke problems

[TCG144]

1998 Yamaha 50HP factory jet drive - 50EJRW remote controls
Motor has no power and sounds like it is missing. Also the tachometer stopped working.

Halfway through a weekend hunting trip my boat started running horribly. I am going to run through the sequence of events, although i am not sure they are all related.

Day 1 I turn the key and there is no power (i have a blue seas batter kill switch), I open the rear compartment and reach for the battery box. As soon as i move the box the lights come on at the console so i figured i have a loose batter connection and thats it. The boat starts and runs fine all day.

Day 2 the boat is fine all day until we are running back to the ramp, i realize that i am almost out of fuel but i can see the ramp so i don't bother to stop and switch to my second (portable) tank. Also i have a 10 micron fuel/water separator so i wasn't worried about suckin Meanwhile i look down at the tachometer and it is dead??? As my buddy is backing the trailer into the water the motor starts to sputter and carry on, I got the boat on the trailer and i FIGURED i was just running out of gas. The tank was almost dry.

Day3 i fill the tank at the gas station proceed to the ramp before light and launch the boat. The boat starts but is running very poorly and sounds like it is missing. I let the motor warm up and it does not change. I try to run the boat but it has no power and will not plane. I swapped out the spark plugs and do what i can in the dark to try to diagnose the problem but nothing changes. Party is over, put the boat back on the trailer and head home.


I have been tinkering for about two weeks now and looking for some guidance on where to look next.
One thing that i thought was strange was that the throttle started to get hard to move. I thought it was the gate on the jet drive but when i disconnected the linkages it was actually the CDI wiper arm. When i tried to move it by hand it is very stiff. How hard should this be to move from idle to WOT??//

** I checked compression with the engine at operating temp and have 110-120 PSI on all three cylinders.
** I have good spark on all three cylinders. (on a side note the engine will start and run with only one plug wire on any cylinder, i don't think this means anything just surprised me)
** I have a newly installed 10 micron fuel/water separator
** I just rebuilt the carbs a month ago with less than 10 hours on them, BUT i pulled them apart anyway just to make sure everything was clear and they are.
** When i had the carbs off I looked at the reed valves and they all looked fine from what i could see with a flash light.
** I checked the oil level sensor by inserting a jump wire between the engine leads and i get the alarm buzzer at the control
** I checked the lower water temperature sensor in the same fashion with the same results
** I pulled the rectifier and bench tested the continuity, I thought it was faulty because one of the wire combinations had continuity both ways?..I bought a new yamaha rectifier and installed but the engine runs the same and the tach still does not work. The new rectifier also tests the same on the bench.
** I pulled all the grounds and made sure that they are good.
** I pulled the battery cables and made sure that they are good.
** I checked the resistance of the primary and secondary side of the coils and i think they are within spec (my meter only reads to tenths so the .18-.24 is hard to see)
** I have power at the tachometer and i also have continuity from the green wire all the way back to the motor at the green wire on the rectifier.

I have a cylmer manual that covers everything from 2-250HP so it is not that great. I have a factory service manual on order and waiting for it to arrive. I also have lined up a DVA meter to test the rest of the ignition components but not sure where to go from here.

 

[TCG144]

Okay i did some more testing today and found the following:

the pulser coils are within spec for resistance but both the load and no load voltage is around 1volt. the manual i have says min 3 & 4
the charge coil is within spec for resistance and no load voltage, but i only had 50 volts under load where i should have 145?
the CDI i measured was only 2volts where it should be 125
lighting coil was within spec for voltage but i measured 4 M Ohm and the manual states <1ohm


I'm not sure what this all means since every portion of the system seems to have specs that are not correct???

 

[99yam40]

Not sure what you are measuring the peak voltages with,
because you need the proper test equipment.
but a DVA adapter works with a regular meter

the wiper should move easily

 

[TCG144]

I used a fluke 87v with peak reading but now that I have read more about the testing equipment even that meter doesn't read these values.

I also used a Simpson analog VOM with the same results.

I guess it's time to drag the oscilloscope out to the garage.

 

[99yam40]

if you want to compare the reading to the specs you will need to get a DVA adapter or a meter made for reading these ignition systems

I did make one that read real close to one made for reading them.

Google DVA adapter

 

[TCG144]

Okay I stopped at radio shack after work and made the DVA.

I tested the pulser coils and had 4.5V & 9V no load /load

Charge coil was 209v & 230v no load/load

CDI output to each coil was 202v

The values are all above the minimums posted in CDI trouble shootin guide.

I checked the lighting coil and the voltage is in spec but manual says 0.56-0.84 ohms but I had 6.1 M ohms.

So the manual says the lighting coil should be replaced, BUT would this make the motor run horrible????

 

[99yam40]

lighting coil charges battery

 

[schematic]

Okay I stopped at radio shack after work and made the DVA.

I tested the pulser coils and had 4.5V & 9V no load /load

Charge coil was 209v & 230v no load/load

CDI output to each coil was 202v

The values are all above the minimums posted in CDI trouble shootin guide.

I checked the lighting coil and the voltage is in spec but manual says 0.56-0.84 ohms but I had 6.1 M ohms.

So the manual says the lighting coil should be replaced, BUT would this make the motor run horrible????

Are you leaving the homemade DVA inplace when checking ohms?

 

[TCG144]

No, I only used the DVA for the voltages. I disconnected the rectifier & blue wire for fuel enrichment from the lighting coil leads and checked resistance across them.

 

[99yam40]

If you get the correct voltage out put I would say it is good

Must be the way you are checking ohms or your meter if you have 4 or 6 MOHMs there should not be any conductivity

 

[TCG144]

I came home from work today and started the motor. To my surprise it ran perfectly fine?? The only thing that was different today than the past two weeks was that it was nice and warm today. The boat was sitting out in the sun all day? I'm not sure if i'm right or wrong but I think my problems are with the CDI box.

 

[99yam40]

If you have good voltage into the CDI but bad coming out to the plug coils, then and only then I would say you have a bad CDI

 

[TCG144]

I have been working on this on/off for the past few weeks. The problem comes and goes. One day I take it to the lake and it runs fine for an hour. Next day it has the misfire.

Over the weekend I rebuilt the carbs. Cleaned them in berry mans they are spotless.

Tonight I went to the lake with a friend and timing light. Start it and the timing light showed that cylinder #2 was not firing correctly flashing about half the time. I had a new coil so we put that on and put it back in the water. Started it up and it ran fine. Check the timing and idle and WOT and set to 7/25 per the spec. Ran it for 10 minutes with not a single misfire shown by timing light. Shut it off and parked the truck. Walk back down to lake, start it and it runs horrible again.

Misfires on all 3 cylinders intermittent.

Any further recommendation for troubleshooting would be appreciated. I'm losing my mind with this problem.

 

[99yam40]

Test with DVA while problem shows up.
That will tell you if miss fire is voltage related.

Kill switch and key switch ground a wire to kill the voltage .
find that wire and disconnect it from CDI to eliminate that as a possibility if voltage is dropping coming out of CDI but good going in while disconnected.


What did you ever come up with on the wiper being stiff?

 

[TCG144]

As far as the wiper, I bought a new CDI unit and didn't make a difference.

I don't understand how a DVA reading is going to show anything in this situation. The DVA charges up a capacitor so a meter can read the peak voltages. Even when missing it is still going to charge up the DVA to a peak.

I will check the kill switch wiring tonight. I don't really see anything else left on this motor besides the charge/lighting/pulser coils.

I did get bad resistance readings from the lighting coil but don't see how that could affect ignition?

 

[99yam40]

there should be a discharge resister in the DVA to bleed off voltage so the cap does not charge up and stay charged. So I would think it would show a lower voltage is it does not get a steady high voltage.
But do what you want

 

[TCG144]

I tested the kill and ignition switch today and didn't make a difference. I went through the checks again and everything was fine but the lighting coil resistance was open. I pulled the flywheel to visually inspect and didn't find anything out of the ordinary but I'm going to order a new lighting coil since it is out of spec and maybe that is why my tach stopped working the same time these issues started.

Not sure how the lighting coil could causing any ignitio. Problems but the one page of the CDI troubleshooting says to unplug the green wires from rectifier and if the misfire stop to replace it. So this system must have some impact on ignition.

 

[TCG144]

99yam40; I wasn't saying that measuring the DVA was wrong, just seeing the way this is missing erratically it might be faster than the circuit discharges. I will try to capture it while running it on the lake. At low rpm it doesn't miss nearly as bad

I appreciate all of the direction and comments you have provided so far.

 

[99yam40]

My C40 had a high speed miss that took me a long time to find. turned out a previous owner drilled out the main jets. I replaced ith new and solved my problem.

If spark is not where the problem is then too much fuel will cause a problem some times. but finding why is a hard thing .

make sure fuel pump is not leaking into the crankcase on # 3 as that is where the pump gets its pulse from

 

[TCG144]

I was certain it was spark related since the timing light was showing misfire. I put the new lighting coil in; the tach started working and the misfire has went away.

Not sure how the lighting coil can affect the ignition but the tech at the Yamaha dealer told me to replace it since the resistance was not in spec.