I have a new non-current 2002 merc optimax saltwater outboard that is idling rough and surging when running wide open. Running wide open it will slow down and decrease rpm's for about a second then return to the higher rpm, almost as if you let off the throttle then got back on it. When I got the boat home I was flushing the engine and it was idling so rough it would turn off, I had to open the throttle a little just to keep it running. It is under warranty and I will be taking it back to the dealer on Friday, just wanted an opinion of what the problem might be. Thanks for your time, John

betcha its fuel related, even if the motor is injected.

crabtrap, I agree, fuel filter dirty, primer bulb bad, or old gas ..... freshfish, put in a bottle of Pennzoil Marine Gas treatment with next 12 gals, change fuel filter, I cant believe the primer bulb is bad on such a new motor???? is bulb relatively new? My guess is bad fuel.... if the above does not work take it to marine mechanic, optimax has a somewhat complicated high pressure fuel system. Several good mechanics available on this form like Rockwall Marine.

Fish More than likley you have some fouled spark plugs the problem is on these motors with the water pickups on the nosecone they would suck up trash and get stuck in the thermostats and cause the engine to run cold causing the plugs to foul.You need to see when you take it to the shop see if all the updates have been done Also if the thermostats are trashed up tell the shop you want the new style thermostats this will solve the problem with running cold and fouling plugs To bad your so far a way I'd work on it Good Luck OPTI

Please don't cry when you hear the price of the plugs.

Please forgive me for being clueless here, what updates are you talking about? What exactly is the nosecone? The changing of the thermostats is that an "update" or will I have to pay for that(will it be an arm & a leg)? Ranger3 go ahead & scare me with the price now. As for the fuel treatment, the boat probably has about 20 gallons in it right now, would you just add the additive to the existing fuel or would you try to run it out then add fresh fuel with the additive or try to drain it (not sure how I would do that)? Might just have to bite the bullet & pay the dealer. I just didn't want to pay the dealer 60.00$$ an hour to tell me all it needs is a fuel additive. Thanks for the help guys, John.

Being under warrenty, just take it in and get your mechanics opinion b4 getting your hackles up. Only fuel treatment to run is a fuel stablizer(Stabil or equivelent). DO NOT use automotive fuel treatments for marine applications. Fuel stabilizer won't "fix" old or contaminated fuel. Best thing I would recommend IF the the fuel needs to be replaced is to siphon or pump out as much fuel as possible, burn it in your tow vehicle, and start fresh using the stabilizer religously.

Spark plugs are not under warranty, it was a costly trip to the dealer to get the plugs changed. It was the most expensive spark plug change to date for me. Granted half was the cost of the plugs but the other half was the one hour of labor. I exhibited the same symptoms you did

As a 2002 no updates s/b needed. If trash was picked up in the l/u pickups it would overheat and cook a power head not foul a plug. I would higly recommend replacing the plugs before taking into a $75 hr shop. Plugs run $12-$20 per plug.

Fershfish, If your plugs are fouled due to the motor running too cold then Mercury will buy them. Like Opti said, make sure all of the updates have been done on your motor. If you want me to check for you just give me your serial number of the motor and I can check Mercury. Call me or e-mail me your serial number at 972-771-4442.

Good Luck, Tommy Yetts
Rockwall Marine

Freshfish, Listen to Tommy Yatts at Rockwall Marine. He knows what he is talking about. In fact take the boat to him and get it fixed... Optimax has a somewhat complicated fuel system.... look on iboats.com and search for "Optimax". Lots of good posts about problem fixes. But Tommy could tell you very quickly what is wrong.

BMCD Just to let you know there three updates that are subject to fouling spark plugs and no the engine will not run hot if trash is picked up and tranfered to thermostats because it will stick the thermostat open and cause the engine to run cold at idle therefore fouling the plugs FYI OPTI