Hello Everyone,

My Name Is Ed Portas And I Just Became A Member Here. Great Website By The Way. I Own A 2003 18 Classic Donzi With A 350 Mpi/ Alpha Drive. I Have A Problem With My Merc. When I Open It Up All The Way It Misses Slightly. I Was Wondering If Any Of You Have Ever Had This Problem And Where Should I Look For Trouble. The Good Guys Over At Donzi.net Have Given Me Alot Of Good Advice Advising Me To Change Spark Plugs And Check The Distributor Cap. Any Ideas Befor I Start Replacing Everything?????

Thanks,
Ed

Before you do that though, are you sure your not hitting the rev limiter? What RPM's are you turning?

Nope, not hitting rev limiter 4500 rpm max. I know it is an issue because it never did it until about 3 outings ago.My first thought was that it was the rev limiter. It only does it at W.O.T. it runs beautifully otherwise.

Ed

Are you sure your tach is right ?

Can you borrow a computer from someone to hook up and see whats going on ?

<All together now? HI Ed! Welcome to the board

Before you go replaceing all of those things why not check them first.....the cap and rotor are the easiest since all you need to do is take them off and take a look. If you have alot of carbon tracking inside the cap you can try and clean it off and see if it helps any. The spark plug wires you can check with a ohm meter....i dont remember what the reading should be but hell check them all and write down what your reading are.....they should all be very close.

But before all those above, i would check your fuel/water sepperator......my guess is that you may have some water at the bottom of the filter and when you are running WOT the fuel moves around enough to start sucking water in the mix giving you the miss.

check stuff first is the easiest and cheapest since its all your own labor to do it. Filter is cheapest to replace first.....then the plugs , then cap and rotor, then the wires. If you go through all that and still have a miss i would start looking at electrical...more likely a sensor that might be going in and out....

After you have checked the things that were suggested above, if you don't have any luck, you really should have someone check the engine computer for active faults and retreive the fault history. At the very least, you could either confirm (overspeed fault with high frequency count) or rule out the rev limiter thing.

Also, there are faults codes which when active, will reduce the available power to 90%, and reduce the rev limit (i think to around 4500RPM). However, such a fault code should trigger an audio alarm of 2 short beeps every minute.

Dave

You should have a small inline fuel filter on that engine. Most likely that is the problem. Replace it first thing. They are known to cause problems.

Ed welcome to OSO.
I agree with Wally. Process of elimination starting with distributor/ rotor.

Hey guys i have some bad news. I changed cap and rotor and engine still misses. I did however have some closure. I had my intermittent alarm go off. The motor only revs to 4200 so I am assuming the miss could have to do with the smartcraft engine guardian. My mech is coming tuesday to run the computer on it. Ill keep you all posted. THanks alot for your input i really appreciate it.

Ed

Dave N,
It Turns Out That You Were Right. The Engine Was In Fact On Guardian Mode. The Neutral Position Sensor Was Shot. The Smartcraft Thought That I Was Revving The Boat To 4200 Rpm In Neutral. That Wasnt The Case, It Just Thought It Was In Neutral When I Would Shift Into The Forward Position. Merc Is Going To Replace All The Parts For Free So Lets See What Happens. Thanks For Your Help.

Ed