1994 Mariner 175 EFI Erratic Spark Port Side

[Skeetin']

Hey all, just rebuilt my powerhead and took my boat out tonight and left the no wake with no trouble. Got 50 yards down the water and noticed a loss of power. I checked my spark under a load and the starboard side has a crisp blue spark, while the port side has one coil completely dead, and the other two sparking intermittently under a load. Looking for some insight on this one. I am thinking possibly a power pack. Brad

 

[Dukedog]

Re: 1994 Mariner 175 EFI Erratic Spark Port Side

If you know what tha switch boxes are you can do this. There is a blue and a red going to one. There is a blue/white and a red/white going to tha other. Swap those from one ta tha other. If tha screwed up firing "follows" tha change ya got a bad stator. If it stays tha same then ya have a bad switch box. Bad box, change both of 'em...........JAN. "pack" is an omc/brp term. :frusty: I bleed V6 anodized/black/gray!..........

 

[Skeetin']

Re: 1994 Mariner 175 EFI Erratic Spark Port Side

I figured I screwed up saying power pack (rookie mistake). This is my first mercury since switching from johnrudes. Thanks for the simple test procedure. I ordered a new switch box this morning so I should have it Friday. Doing a lot of research and it seems to be the common problem for a lot of people. I will do that test this afternoon and post results. Thanks

 

[Dukedog]

Re: 1994 Mariner 175 EFI Erratic Spark Port Side

We'll let it slide "this time".........:lol:

Yeah, pretty easy test. Still recommended ta change "both". A bad "bias circuit in either box can lead ta a missed diagnoses of which box is actually bad. In other words a box with tha bad bias can actually fire good but take out tha box that is actually tha good box. Clear as mud, huh. Tha circuit has ta be tested ta make sure ya get tha right one and its not "always a good test". Even tha factory Merc guys will tell ya ta change both..........jmo

 

[Skeetin']

Re: 1994 Mariner 175 EFI Erratic Spark Port Side

That makes sense. Run into that problem a lot on fords with the 4.6 and 5.4's. We call them ghost codes where testing indicated one coil to be faulty while the real culprit is its opposing cylinder. I figure i will try one and see if it fixes the problem and then get a spare on order. But I am going to check the stator this afternoon. Worst case if it is the stator i will have a spare switch box. Seems to be an item that is a time bomb on these engines. Thanks for the info Dukedog and I will let you know how the results come out. Last question, which one would you say is a more common failure, the stator or switch box?

 

[Skeetin']

Re: 1994 Mariner 175 EFI Erratic Spark Port Side

Well, I checked it out tonight. Ohms were way off the scale for the stator specifications. Looking like Im in the market for a stator now. Should i go ahead and replace the regulators while Im at it?