08 250 Pro XS miss at WOT

[Lagoona]

Looking for help on a miss/hesitation at wot. My plan is to take this motor to a Merc mechanic when one becomes available. Currently the wait is two weeks. However, I still have guided trips planned.
2008 Mercury 250 Pro XS Serial Number 1b722287
The first issue I’ve had is with the voltage alarm after trimming the motor up or down for a few seconds. The first time I noticed a miss was maybe a trip or two after that. The next outing I could definitely tell there was a slight miss at wot. They next day I replaced the gray fuel line, fuel filter, spark plugs, and rebuilt the pulse pump. This seemed to work... for a few minutes. But the miss came back. And so has the engine alarm. It flashes every time I start the engine 8 times in quick succession. (Not 4 times... 8 times very fast) And it does this every couple of minutes after.
I then brought it to someone who agreed to print out the module summary or freeze frames.
TPS 1 No Adapt. Frequencycounter 8. runtime 293.4 (was the current run time) volts 10.12
Overspeed in neutral. Frequencycounter 32. Runtime 292.5. Volts 10.87
Battery Range Low. Frequencycounter 14. Runtime 289.7. Volts 11.36
Fuel Injector6 Open. Frequencycounter 10. Runtime 273.9. Volts 12.22
Overspeed. Frequencycounter 0. Runtime 271.1. Volts 13.95
The next day I purchased two coils because I had notice to of my coils appeared to have bronzed slightly corroded looking ends. I cleaned them with a brush but decided to just put the new coils on. No difference. I then checked the other 4 coils. No difference.
A mechanic looked at my report and freeze frames. He noticed the low voltage. I explained that it might be due to my graphs and live well pump. My battery is a one season old Duracell 31 Agm from sams club. It’s parameters are 1000 mca 800cca 105 rc. It has never had trouble starting the motor and is charged every night after use. I took the connections off and cleaned them well, putting them back in proper order with main motor on bottom. It didn’t seem to make much difference, voltage is still 12.3-12.7 at start and quickly rises to 14 per smartcraft gauge. I brought the battery into O’Reillys tonight anyway and had them do a couple of tests in which they told me my battery was fine.

The couple of mechanics I have talked to did not seem to think the TPS would cause the miss at wot.

I'm limited in my abilities as I am not a mechanic, nor am I flush with tools or the knowledge to use them.
The motor seems to run fine up to 4000 rpm. The new wot seems to have now dropped to 5200 before it really misses and stutters. I plan on using this motor for guiding the next week. I’m concerned that I’m going to hatch it.
I’ve been reading these forums in excess, and am hoping you can help me as well as you’ve helped so many others. Thanks.

[Bob G.]

You might want to look at your battery.

http://www.bbcboards.net/showthread....batteries+meet

[Rip Bass]

All of the issues you mentioned point to low voltage. That battery you have is just barely enough for the engine only,with no extra amps for any of your other devices. You need more MCA and reserve.

[Lagoona]

I believe I made a mistake when I posted this batteries reserve cap. It is 200 with 1000mca and 800 cca. It is labeled as duracell but it is my understanding that it is a rebranded deka 31 as recommended in the recommended batteries. And when it was tested, the guy told me it was good. ?

[Savage]

The battery voltage at the time of your faults is TOO LOW. Having said that you do have multiple issues, but the voltage needs addressed FIRST, since it is so obvious!

[Lagoona]

The battery voltage at the time of your faults is TOO LOW. Having said that you do have multiple issues, but the voltage needs addressed FIRST, since it is so obvious!

Savage, what would your recommendations be on things to check?

[Savage]

Load test battery
Check ALL the wiring/connections
Test charging system
Charge battery BEFORE EVERY outing.

[Lagoona]

Load test battery
Check ALL the wiring/connections
Test charging system
Charge battery BEFORE EVERY outing.

All of these things have been done, done routinely, or checked. I took the motor out last night and noticed that the alarms eventually shut off for the first time. However, the high speed miss is still present at 5200-5400 rpm.

[Savage]

Well something was missed because the battery voltage at the time of some of the faults was BAD.

[EuropeanAM]

Current problems:

-BATTERY VOLTAGE. Start at the battery with a LOAD TEST, you need 950 CCA or higher test results.

-Connections: Recommend using clamp-style connectors with ENGINE CABLES installed FIRST, remaining largest to smallest and finish with a Stainless Locknut.

-Check voltage AT THE BATTERY with the engine RUNNING. If voltage is not climbing into a range indicating that CHARGING is occurring (13.1 or higher), test alternator circuits.

-DON'T MOVE THROTTLE unless engine is running, in gear, and going somewhere. TPS Maladapt Faults are often operator-induced (throttle being applied when started).

-CHECK FUEL INJECTOR CONNECTORS- ESPECIALLY #5 and #6. Corrosion or harness problem exists on #6.