2000 Mercury 200EFI intermittent loss of power, SN 0T158142

leonreno, thanks for the suggestions. I managed to forget my electrical tools at home when I went on this trip, so I did not test the voltage or spark. I am hoping that the problem will manifest itself next time I have a chance to work on it. I will have my tools ready.
I tested the stator at the end of last season and it checked out. Now that you mention the regulators, I did notice that the tachometer was acting wacky and jumping around on several occasions this trip, but only when I was trying to start the motor. Perhaps that is an indication of an electrical issue?

Possibly, though mine did that one time and I turned the switch on the back of the tach back and forth and it stopped doing it. The contacts can build up a little corrosion and switching back and forth helps remove it. Have you inspected the regulators and all the connectors for burnt spots?

I have visually inspected all the wires including the stator, trigger, and regulators. I unplugged, cleaned, and applied dielectric grease to almost every connector on the motor. The only thing I observed that looked out of the ordinary was damaged insulation on one of the trigger wires. It did not appear burned but rather chafed or pinched. I did not see any damage to the underlying wire itself and covered it with liquid tape. Since I clearly still have a problem, the trigger is now on my list of parts to replace.

I will definitely update as soon as I have a chance to work on the boat, but if any of these symptoms ring a bell for somebody - I would appreciate some guidance.

Given your last few rounds (and the length of this thread), it's probably going to be in your best interest to get some hands-on expertise involved.

Could be something as simple as the ECU connector, keyswitch or harness, lanyard switch, or most any other electrical component on the engine.

Don, I would love to hand it to somebody to fix but I do not know a knowledgeable and honest marine mechanic in my area. My experience is that the average marine tech (or any other trade)...is average at best. I am an engineer with plenty or automotive repair experience, have tools, and a factory manual. I would dare say that I am as "good" as the "average" mechanic, just slower. With few exceptions, if you want it done right - do it yourself. The only thing more frustrating then the motor dying on the water is the motor dying on the water after you just paid somebody a bunch of money to fix it! If you know a knowledgeable and honest marine mechanic in Central or North Alabama, I would love a referral.

I have already tried to address the simple things - unmated the ECU connector, cleaned it with CRC contact cleaner, visually inspected for corrosion, applied dielectric grease, re-connected and secured with zip ties. Almost every connector on the engine got that treatment, and the one on the control box. I plan to break down and clean/lube the control box to replace the cables (unrealted to the stalling issue, just getting tight because the cables are old). I will further test the key switch and lanyard at that time. The challenge is that I am yet to experience this intermittent problem when I am in a position to troubleshoot it. When it finally presents itself when I have time and tools, I am confident I will be able to at least narrow it down.

It was my hope that suggestions from this board would help me find and fix the problem faster.

https://www.mercurymarine.com/en/us/find-a-dealer/

See if you can locate a Transom Mounted Keyswitch Harness (or a known-good keyswitch harness that can be plugged directly into the engine).

Run it and see if you can replicate your problem (I have seen a couple of keyswitch problems that would act like this- ALWAYS worked on the trailer, of course).

I have my own keyswitch harness that I use to isolate issues in other ppl.'s boats,that does eliminate alot of small issues,another thing you may try,is isolating your boats fuel tank,by using a separate fresh 5 gallon tank,you may have something as simple as a bad or plugged vent,or something in your tank that plugs your pickup screen.

Quote:

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Originally Posted by EuropeanAM

https://www.mercurymarine.com/en/us/find-a-dealer/

See if you can locate a Transom Mounted Keyswitch Harness (or a known-good keyswitch harness that can be plugged directly into the engine).

Run it and see if you can replicate your problem (I have seen a couple of keyswitch problems that would act like this- ALWAYS worked on the trailer, of course).

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Gentlemen,

Thanks for the suggestions. I will definitely try both. I still think that this is an electrical issue and not a fuel issue, but I cant rule anything out yet. I hope to have some time to work on the boat in about 2 weeks.

Its been a long time, and I have not used the boat in about a year. Today, i changed the fuel filter, changed the impeller, and the gear oil. Motor fired right up on the hose, and i let it run for the 15 mins. Fuel is a year old, but is ethanol free REC90 with Stabil added.
Everything looked good, so i dropped it into the lake. Ran around in the lake for about 30 mins at various speeds, from 3500 to WOT. Saw 5400 trimmed out. Everything was great until... as i dropped back to idle coming in to dock, the engine stalled. Restarted but kept stalling. After several attempts, the motor would not restart. I was able to tie up, and started troubleshooting.

I was able to verify spark on all 6. Fuel pressure was 35psi while cranking. I pulled the intake cover and the injectors were spraying. I rushed this part, as a huge thunderstorm was rolling in, and i am not sure all were spraying and did not inspect the spray pattern. All through this process, i was periodically attempting to start the motor. I had some starting fluid, and after a just a brief squirt, the motor fired up and kept running. I am at a loss now...What is going on? Dirty injectors? What to do next? Please help!
Its going to spend the night at the dock, but tomorrow i need to run about a mile to the ramp. Hope to do it under my own power.

Several notes - i measured fuel pressure at the schrader valve on the VST.
When i pulled the intake cover, there was some black gunk on the throttle bodies. Is that normal? I will try to post a picture once i am by a computer.

https://media.fotki.com/2v2JCAieuxu2B8k.jpg

https://media.fotki.com/2v2JCAiBExu2B8k.jpg

If you are interested in getting the intake clean. Take the intake off and send to don. He cleaned my intake and the injectors. There is a small hole in intake for the map sensor pressure, make sure it is free of debris since you have intake cover off. Its where the black tube from ecu attaches to intake.

Haughton, thanks for the suggestion. I plan to do just that.
This whole time I was under the impression that my problems were ignition related, so cleaning the injectors was on the back burner.
Since I was able to confirm spark on all 6 while the no-start problem was occurring - does that leave ECM, clogged/bad map, and AIT as possible culprits? The MAP is internal to the ECM, right? Anything else?
Can a mechanic with proper diagnostic tools "plug in" and see the sensor data live? Is this something that I can test myself?

above you said inj were spraying #29, and you have spark on all 6, good fuel psi, possibly bad fuel , had you recently added fuel ????

Fuel is a year old, all 75+ gallons of it :) However, it is REC90 with Stabil and Seafoam added. In my experience, while not ideal the fuel should still be good. I seems that bad fuel should cause the motor to run poorly all the time - slow to get on plane, etc. The motor runs about perfect until it gets hot, and then it will not idle and dies. Also, the last time I had this problem - the gas was fresh. Is my reasoning wrong, am I missing something?
Here is my plan of attack next time I work on the boat:
1. Test fuel pressure at key turned, idle, 15/30/60 seconds.
2. Check vacuum signal at fuel pressure regulator
3. Check vacuum signal going to MAP (Is the MAP internal to the ECM? I plan to check/clean the intake port and the vacuum tube.
4. Check IAT.

Hopefully, the above produces a smoking gun. If something looks suspicious, I will repair and test on the water. If nothing is obvious, I don't really know what to do other than check/rebuild the ECU.
Regardless of what I find, I will send the intake and injectors to Don for cleaning - but I would love to find the cause of the problem first. Any other suggestions?

map is internal,cds can read it, but map will not cause no start, reasoning not wrong

My comment was due to dirty intake and cleaning the map intake since you already had intake cover off. Just preventive items not due to no start, sorry for confusion on that.

^^^^^ good advice also :thumb up2:

I know that this is moving at a snails pace, but such is my life right now. 2 small kids keep me busy. I did however want to update this thread because I spent a little more time troubleshooting. No smoking gun so far. I am frustrated as ever. I am ready for somebody else to take a stab at it, but every Mercury certified shop around is booked solid for the next 2 weeks.

My prime suspects were temp sensors, and MAP sensor. I removed and tested the air intake temperature sensor, as well as the cylinder head temperature sensor. Both seem to test OK per the manual. I tested over points, with ice water, room temp, and hot tap water.

AIT: 8.62kΩ@72F, 24KΩ@32F, 4.3kΩ@105F
Head:1.05kΩ@72F, 2.75kΩ@32F, 0.47kΩ@105F

At this point, I was really hoping to find a clogged port or vacuum line to the MAP sensor. Port was clear and vacuum line does not seem have any obstructions.

I will run the motor on the hose tonight and will check vacuum to fuel pressure regulator. If that checks out, I am not sure what is left.
https://media.fotki.com/2v2JqJQ62xu2B8k.jpg