ID replace the IAC, might have to open the butterflies just a tad with the idle screw, I had one that looked normal on the laptop but would not idle right and stall when put in gear, replaced it and new plugs and was fine....wheres the TPS volts suppose to be set,

If a plug is not firing, or not firing very well the ECM will change the timing frequently (milliseconds) to try and keep the rpm stable. The spark can be making it down the wire but not jumping the spark plug gap. This is why I asked for the individual plug wires to be pulled. Pulling individually also can listen if the change is about the same or different

Yeah, I didn't pay attention to the year. Regardless, this is a fuel issue, and as such I would look at how it is supplied, returned and vented.

when running one thing off the bat IF YOU HAVE MEFI 3 ECM then you have low fuel pressure unless your gauge is not accurate. And is that a bouncing needing in the pic as looks to be ? or is the needle steady eddie ??

I do not know which MEFI you have because I did not see any engine serial number posted. That is a must for all marine engines.. Engine serial numbers is how all marine engines are set up, correct service procedures and all related specs - Year model really means nothing

That's called power balance testing ^^^^^

and you use a digital tach to help with testing. You have to be quick watching the tach cause the IAC will compensate and help pick up the rpms fairly quickly in most cases.

how old is the ignition coil ? and the correct one needs to be used - the primary and secondary resistance needs to match the OEM coil. They all look the same from all different sellers out of the box but they are not internally. The coil windings and so forth are important for spark output for a jist of info.

Totally wrong info about spark plug wires actually in marine apps they ARE OFTEN NOT CHECKED NOR CHANGED ENOUGH, must have been an auto mechanic that mentioned all that for they rarely ever need changing. .. .

There is many reasons why spark plugs wires in marine apps need to be changed and correct wires as well. The main issues for a jist of it ----- For one is the heat soak in an marine engine compartment last for hours and is way hotter than an auto would ever be. Also the gas fumes breaks down rubber and plastic components over time. And if one does not think gas fumes are not an issue - why is it USCG mandated that all boats have a bilge blower -- to evac gas fumes before engine start up. Marine engines compartments breed gas fumes 24 hours a day,

Anyways -- I did a lot of testing with Moroso for spark wires and another issues with off the shelf spark plug wires is the suppression needed against RMI and EMI. Basically electrical noise that interferes with efi systems and other components.

marine techs on top of their training -- ohm test spark wires all the time and check for corrosion inside the boots, spark tracking, discolorations and other things

ok I see what your getting at. how much should the timing be changing under normal condition's (ever second or couple seconds?) I will pull them individually next time I pull it out of my garage, probably tomorrow.


It is MEFI 1 according to the scanner. The serial number is OLO14516.

could I use the tach that is on the scanner? or do I need the mechanic style that connects to a spark plug?

Im not sure of the age of the coil. I know I never changed it so its at least 4-5 years old.

For the most part it would not stop moving, changing constantly

i was able to get the boat out today and run it (on muffs). I did not notice a difference pulling the spark plug boots off one at a time. I did shut it off and re-start it.

I installed all new plugs, a new cap and rotor. I did not replace the plug wire's because I did plugs, wire, cap and rotor last year also. I also checked the timing, it was at 6.5-7 BTDC. I changed it and got it as close to 8 as I could. I on the muffs I am not sure if any of this made much of a difference.

here is a video I took of the fuel pressure gauge while the engine was running to show how much the needle move's. I thought this was normal but honestly this is the first time ive ever check fuel pressure. I could not figure out how to upload it like I did with the pics so here is the you tube link.
here is a link to a video I took to show how much the spark advance is changing. I thought it was normal but that was normal but again I don't have a ton of experience with this scanner yet to be able to say for sure.