had a fuel gauge on all last night. It was the manual gauge at the fuel rail. It help 42lbs at idle and all the way threw. Right where it should be. Fuel is very clean as well. Unless its in the injector im a leaning more for a spark issue. Is snaps an an off. The one wire I had change was sliced pretty good and if it was arching Im wonder if that would mess up a coil. Wish there was a simple at home way to test them for proper output.

no 4bus, Im not holding my hand on them to see what kind of shock i get :)

A miss fire should show up on the scan tool.

Not one misfire code, but I can tell you it is definately misfiring. The fact that this engine has been modified, and the MEFI4 ecu was useds makes me think it no longer tracks misfires on the ecu.

I am still saying one of the coils, or one of the new spark plug wires, but Gayboat....I mean Jboat won't listen to me :lolhit:

One of these....like I suggested monday :/

http://www.wayfair.com/Waekon-Indust...FUSK4AodK2zrZA

what about this,,,say the first new crank sensor was good,,you might have a bad wire at the plug ,or a broken wire,,going to the sensor

Just wondering. When the boat fails. Will it still miss at idle ? If so You should be able to pull plug wires to find the cylinder thats missing or read the plugs. Wet plug missing cylinder ??? Just asking. Hate trowing money away for nothing. Artie

i had the same type of problem, on my starboard 496. Had no balls then after about 10-15 mins ran strong. I hooked up my rinda scan after it cooled down & did the induced misfire test on each cylinder. found #7 wasnt changing the rpm's. Got back home did the injector test on #7 sounded fine, took plug wire off stuck a new plug in it & did the spark test on top of the engine so I could see the spark, was good. Installed the new plug & engine has ran strong with no issues since. Been almost a year now

JETDOC - I hope I have the same issue.

Well another week into this and still stuck in the same place. Took the boat to the Merc dealer here and they said 3 ½ weeks before they could even look at it. That’s pretty said, our summers are too short for that. I pulled it back out and its off to a side shop that does not know them motor well but is will to check the plugs, spark and injectors for me. I would have pulled the plugs a while ago but the exhaust will only let me get to 2 or them with out having to pull the manifold.

So here goes week 3 and hopefully he can narrow the field a bit for me this week. I just hope all of the plugs are not coming out wet. I had a local Chevy mechanic who knows the truck version of the 8.1 well on the phone and he thinks the computer might be dumping to much gas and not letting it out of warm up mode. He thought it could be a sensor reading a low temp. From what I saw on the scan tool however everything is in range with the exception of a -40 intake temperate reading. There however is no sensor at all for that and Crocket told me it should be turned off on the ECM.

Think we finally got it licked today. Paid the 4 hours labor to pull the manifold and get the new plugs in. Had 6 nice light brown plugs and 2 very black ones on the port side bank. New ones went in and she ran like it should tonight. Just hoping Im not going to have a re-occuring issue as they are not easy to get to. The bad plugs are attached.

Wow really. Dam hope alls well. Artie

Scan tool should have found that