Mercuiser 5.0 thunder bolt V ignition start up and running problem.?

Question

When I start up the engine it gives out alot of black smoke for a couple of minutes until the engine warms up, it looked not very normal to me, and I decided to replace spark plugs, wires and the distributor cap.

I found that the spark plugs have oil on their threads, is this normal?

After replacing them now my engine is worse, I think I messed up something. The engine still gives out alot of black smoke when it starts up and after switching the control in to idle position the engine stops, and when running at throthle it sounds like something in the engine jumps or hits once in every minute or so.

I need help.

Answer 1

This is an interesting question.  Reading between the lines, when the engine is cold, you are running way rich.  Then once at temp, you can't keep it running?  First check to make sure that you didn't accidentally cross two spark plug wires.  Then check to see if any of the sensor wires are disconnected.  You didn't give the year of your engine, so I don't know if it's carb, or injected.  If carb, it has a thermostatic controlled choke, it sounds like it's stuck.  The cap has firing order and it's easy to connect the wrong wire to a plug.

Answer 2

You do not give all the details, however, I can tell you the following:

1.  black smoke on start up usually means the engine is running rich, which means that the engine is getting too much gas in relation to the air.  A sticky choke can cause this, check that first.

2.  Oil on the threads of the spark plugs is also a sign of richness.  It can also mean you are pumping oil, which can mean you need to rebuild the engine.

3.  It appears that you might have a plug wire placement problem, check the firing order, match it to the order on the engine, if you do not know what I am talking about, go online at chevyengines.com,(these mercruisers are just chevy car engines) get the firing order and check to make sure you have the correct firing order.  

Good luck, if you have fi on your engine, then you may have a programming problem, get a pro to check it out if that is the case.