HELP!!!! Merc 350MPI problem! Sputtering
 

I am in need of some educated help and fast. My wife and I drove our 1998 29.5 scarab from Miami to key west yesterday and along the way the port side engine began to sputter. I noticed that it is missing under load at 2000 to 2600 rpm's. It is fine at idle and it will miss a little around 3,000 to 4,000 but it is very bad at 2,000. My first thought was a bad spark plug! We are traveling light so I do not have any major tools. I am sure I can buy what I need locally but I don't want to have to spend any $$$ that I don't need to.

Check your grounds on the engine. Could be a million things but I jst had that one.:D

thanks
 

Thanks for the input. I took a look and things look fine. I think I am going to find a mercruiser mechanic. If anyone knows of one in the key west area please advise.

When was the last time you had a tune up? I have seen on these engines where the cap is so corroded under the top that I was surprised it was running. Would start up and idle but didnt want to run very good on plane.

Just a thought.:D

great help!
 

I can't say thanks enough for taking the time to help. I looked at the cap and the screws holding the top on are corroded so it looks like that could be it. I found a local mercruiser mechanic who is going to look at it in the morning. I will pass along your idea of what it may be. Again thank you!!!!

So the merc mechanic flaked out. I cleaned the points and still no dice. the motor will not fire up at all now. The rpm gauge is moving when turning it over but i am having low fuel pressure. We shot starting fluid in the intake and cranked it over and still no hint of a fire! Makes me think it is an ignition issue. Any idea????

How are you determining that you have low fuel pressure? If it doesn't start when you spray starting fluid in it, then you most likely have an ignition failure.

Assuming it is a ignition failure, and you are showing a signal on the tach when you crank the engine, that would suggest you your ignition sensor is ok and generating a reference signal for the coil, but you are losing it (spark) either at the distributor cap, rotor, or coil wire. Possibly but less likely, you could have a bad coil.

It may not work just to clean the terminals in the cap (i assume thats what you mean when you say you cleaned the points), replace the cap and rotor if possible. If you have access to a ohm meter, check the coil wire for an open circuit.

Dave

I had an original merc tach develop a fault while on a run and cause the same problems - disconnected the tach and the ***** purred like a kitten.
(It took a 6 pack and a couple of hours to find this one):cool-smiley-011: