2007 250XS Idle issue when warm

[cannon20xrd]

Serial # 1E003251 bought new in 08 @ 600 hrs. Always run a fuel cocktail in every tank.
Started up and ran fine as normal, fished for several hours without issue, but on one start-up after fishing a spot for 20 mins the engine started but idled very rough and stalled, 2 more attempts with the same results, with a lot more smoke the normal. 4th try I was able to get it in gear and throttle up and get it on plane without any alarms or performance problems, It ran fine up on plane at 4k rpm. So I stopped and turned off the motor waited 10 seconds and re-fired no problem. So I continued to fish a few more hours but every time I let the motor set for any length of time, the same problem would occur. One attempt to re-start the engine went to a fast idle and I got the high rpm in neutral alarm but stopped when idle slow to a rough idle. I did notice if I trimmed the motor up while fishing a while it seemed to help restart, not as rough an idle it seemed. Got it home and the next day put it on the hose and fired it up no issues, several restarts and still no issues until I let it sit for a while after the engine had warmed up. Any ideas ?

So far I have performed the following tests-

Inspected spark plugs they have less then 50hrs and look good, light to medium tan gapped at .042
Checked the tracker diaphram for holes - all good.
Air pressure at rail -95 psi / maintained pressure for 10 sec (mercury racing spec)
Fuel pressure at rail- 112 psi / maintained pressure for 10 sec
Compression- 120-125 on all 6
Reed valve inspection, no visible chips, cracks or broken reeds will measure gaps tomorrow.
Visual inspection of fuel injectors, very clean no corrosion or build up on tips, o-rings good.
Visual inspection of Air injectors , very small amount of carbon on tips wiped of easily, o-rings good.
Inspected thermostats and tested open at 130 degrees-no debris found.
I will do a spark test after I reassemble. I think I will install a new set of reeds while I have it down as well as get the injectors cleaned, but they look so good almost seems a waste..lol. But I want the piece of mind since its never been done. Reeds were done once 300 hrs so might as well, may give the TDR's a try.
Need some help as to what to try next ?

[Savage]

Try pumping the primer bulb until it gets hard before starting the motor. Take note of the number of squeezes that it takes to get hard.

[cannon20xrd]

Thanks Savage, been there done that has never made a difference with this motor over its 13 year life.
So I'm leaning towards and intermittent spark issue maybe a coil or maybe an injector... no idea.
I have tried a different set of plugs with to change. Starts up fine cold, runs fine on top, set down and fish, restart fires up idles rough stalls, re-start until I can get it in gear then WOT gets on plane runs fine, set down seems to idle fine. Turn off motor, quick restart no issue. Let it set awhile and here we go again. Same thing when I have it on the hose, but last time on the hose when it started missing or rough idling a detected a distinct clicking out tapping sound momentarily. Not the normal ungodly sounds the opti's are known for.

[cannon20xrd]

Any other ideas ? Suggestions ? Don at European marine ?
More testing-
Checked Ohm resistance on the fuel injectors ( 2.1-2.2 ) on all 6
Air injectors - (1.6-1.7) on all 6
Drained fuel from VST - no water or debris.
After pulling and inspecting the reeds, I do have a few that are out of the .020 spec. I will be ordering some TDR's on Monday.

[Bob G.]

I would try what Savage recommended first.

[EuropeanAM]

And despite testing the thermostats, you really need to check the actual temp of each bank of cylinders (either on the CDS, or with a hand-held Infrared Temp Gun, pointed right at the center of the t-stat cover).

A cold-running engine will do just exactly what you are experiencing.

[cannon20xrd]

Thanks Don !
I will test that next,as soon as I get it back together. Should I expect the temperatures to read 130 or a bit higher ?
I have a contact temperature probe that plugs into my digital volt meter, I assume that will work on the t-stat covers ?

[Savage]

Temperature probe in DVOM will work.

[EuropeanAM]

That's marginal... one is reading the surface temp, the other is depending on conduction of temp from one OBJECT to another in order to read the temp.

Temp probes work best when IMMERSED in liquid (as compared to touching a solid object).

You are testing to make sure that both banks are coming up to 120 degrees or higher (in the center of the thermostat housing- don't attempt to take temperatures from other areas of the head as they are quite commonly inaccurate).

[cannon20xrd]

Thanks guys , I will see if I can get my hands on a infrared temp gun.

[Savage]

If you hold the probe against the cover it will get the job done for what you are looking for. I have a Fluke probe for a DVOM that picks up a reading with or without contact, or immersion.

[EuropeanAM]

If you hold the probe against the cover it will get the job done for what you are looking for. I have a Fluke probe for a DVOM that picks up a reading with or without contact, or immersion.

Thanks, Savage. Admittedly- mine never got used as a "contact" probe- but it's good to know it will work this way.

[cannon20xrd]

Thanks Savage. I may have found the issue, i picked up my injectors from the shop and was told one injector was was partially clogged and doing more dripping then spraying. Putting it all back together over the weekend and will see if that truly was the issue ...I hope so. I will report back with the results.
Thanks for the help guys

[cannon20xrd]

Well, after installing new TDR reeds per Don's recommendation also did new thermostats, new plugs, injectors cleaned,and a new belt idler tension spring .......I'm back to square one. Start up seemed a little rich to be expected with the oil prime sequence and pre lubing reeds. After warm up the miss / rough idle started again.
#5 plug looked fouled so I replaced with a good plug , no change, swapped coil on #5 with another.... no change. The last test at start-up the engine raced to a high idle maybe 1500 rpm got the over speed alarm so I shut it down. Restarted engine and again it rev'd to 1500 or so but this time it slowed back down to normal idle speed but there is a distinct miss.. ??? No alarms otherwise ?? What im I missing ???
Any thought s Don ?

[Savage]

Better look at the tracker valve again, and/or the pulse pump.

[cannon20xrd]

Will do, thanks

[cannon20xrd]

OK guys here's what I have found after after weeks of testing and troubleshooting.
1- Pulse pump spring broken, rebuilt pump still having a miss at idle and now at WOT,. ( Thanks Savage )
2- Kv spark tested all 6 all good
3- Pulled the plugs, #4 plug wet installed new plug re-tested #4 coil -OK
5- ohm out the #4 plug wire tested good
6- Retested #4 with the spark tester and BINGO ! intermittent spark. If I pushed on the coil harness plug I could stop the spark.
I found the red wire in the plug was broken making an intermittent connection.
"""So how do I get the terminal pins out of the plug"""", I can seem to find the right combination to remove the pin so I can fix the broken wire. Its broken right at the plug a 1/4'' from the terminal pin.

[Savage]

Buy a new repair connector and splice it in.

[cannon20xrd]

I have a couple on order , but I would like to make a temporary repair so I can make a few test runs to verify all is good

[cannon20xrd]

I may decide to replace the complete coil harness but the part#s and revisions are confusing and show a different harness layouts.
Can someone help with the correct part#
SERIAL # 1E003251 built in july of 2007, tag on the harness is 8M3000247 Rev B