4.3 mercruiser strange problems

[Matysek1]

Hello all first post but not new to forum great place for information I got a 4.3 mercruiser serial 0l695756 mated to a alpha 1 gen 2 in a 2000 sea ray 185 problem I'm having is it starts up great and will idle and rev perfect after a couple of minutes will start to slow down and miss on a coulpe of cylinders will never die I can shut it off start again and fires right back up then a few minutes same thing I changed all the plugs to the right ones and same thing I'm lost now

 

[alldodge]

When you restart, do you pump the throttle to restart or just turn the key and it's OK for a few minutes?

Have you changed the fuel filter?
Have you poured the contents of the filter into a clear container to check for anything but clean gas?

 

[Matysek1]

Just turn the key never have to give it gas. I will be taking both filters out today just weird that it starts to miss checked compression on all cylinders all good confirmed that was missing by pulling plugs while running with no change in rpm on certain plugs

 

[alldodge]

starts to miss checked compression on all cylinders all good confirmed that was missing by pulling plugs while running with no change in rpm on certain plugs

In this case I would look at plug wires, cap, rotor and plugs. Might be your wires are breaking down

 

[wahlejim]

First thing to do is isolate electrical issues from fuel issues. Try running on a remote tank and see if the problem is still there. If it remains, we can look at the engine, if it goes away, then we can look at the tank, anti-siphon and vents.

 

[Matysek1]

Ok can these coils break down and cause a missfire or just a no start

 

[alldodge]

Ok can these coils break down and cause a missfire or just a no start

Yes they can, but a coil is hardly ever the problem, and more so in your case. You said that when a plug wire is pulled it doesn't change the rpms, if it was the coil it would not be just 1 or 2 cylinders

 

[Matysek1]

Ok that's what I thought when I do pull a plug you see it arching like crazy just not firing to the plug

 

[alldodge]

Well, we all keep saying, ya need to give us all the info, not just a piece of it. If your original post was something like

I'm having is it starts up great and will idle and rev perfect after a couple of minutes will start to slow down and miss on a couple of cylinders will never die I can shut it off, turn key without touching throttle and start again and fires right back up then a few minutes same thing I changed all the plugs to the right ones and same thing

checked compression on all cylinders all good confirmed that was missing by pulling plugs while running with no change in rpm on certain plugs. When I do pull a plug you see it arching like crazy just not firing to the plug

Then my first question would be where MR43LTS installed and gap of .045 ?
If yes, swap plugs with another location and see if the miss stays at current location or moves with plug.
If it moves its the plug if it does not then wires would be my guess

 

[Matysek1]

Sorry my bad. New plugs were put in yesterday and we're gap correctly the po had two autolights plugs coincidence where it was missing changed plugs and same thing fires right up on all cylinders then feels like two drop out

 

[alldodge]

If you can swap some plug wires around trying to get it to follow the wire to confirm that is the issue. In any case does appear to stay on the same 2 cylinders, so that is cap, rotor, wires or something with the cylinders

 

[Matysek1]

I'll start moving wires around today I checked compression was 135-140 across all six