If the boat sat a long period of time more than 2 months pump out the fuel put fresh gas in Order the correct gasket set first for your carb unscrew the top half of carb only be sure to disconnect idle bar in back of carb held on with "C" clip . Remove center low idle /high idle ports inside carb should be tree screws ... if you have a air compressor blow the tubes out so there are no obstructions replace with new gasket . Clean out idle screws inside bowl float area blow them out put them back after cleaning the rest of the carb with carb cleaner ... replace new gasket reinstall top of carb back do not remove the whole carb just the top ... tighten screws back down turn in air mixture screw on side of carb in to seated position then back out screw 1 1/2 turns only ! That is factory setting if idle is still ruff pull the ignition rotor cap check for corrosion if main coil prong looks burned than replace cap with sierra brand cap ... if the timing is off there are videos to reset timing it requires a jump wire you can make that puts it into base timing you need a timing gun of coarse follow the steps in the video all of these procedures will solve your problems I know I learned the hard way myself I hope this helps you all out good luck 👍🏻

You may need to adjust the automatic choke depending on weather. Set it to slightly open with engine cold and weather hot. this will let it open sooner in hot weather and reduce over rich condition. In colder weather you can readjust. Some people turn key on for a minute or so to get choke to start opening before starting, but if you have older points distributor you will burn the points... so just set the choke to prevent this.

Thank you for cutting off the blower

Flooding, plus a too high idle speed which is giving it enough air to try and keep running. Fix carb flooding, possible float setting or faulty needle and seat. get to operating temp and then set idle speed to spec. Extremely common on cars also.

On occasions I find mine won’t start, so I close and hold the carburettor flap with the back end of a screw driver as on occasion it has spat flame from here, and it starts immediately, on my mercruiser 3.0, this flap opens not when engine is hot but if ignition is left on, it appears to be an electronic choke, if I’ve left ignition on with engine off while launching boat I may find the choke fully open with a cold engine, so manually closing the choke allows for an easy cold start. I learnt this the hard way,, sitting on the slip, trying to start when boat after boat would launch start and leave and I was sat there like a lemon trying to start engine, don’t worry I wasn’t blocking slip, we have a pontoon for 8 boats and a slip for 3 launches. But it’s disheartening, to be the first down and the last out when you have a 4 hour window unless you go across the tides. Since learning this I now Leave keys out engine until I’m ready to start, and if fails to start I fully turn off ignition, second attempt I’ll set the throttle to nearly full and start and usually fires, if it starts I immediately drop throttle to neutral, if it doesn’t, switch off and back to a little throttle and try again, if it hasn’t started by second attempt it has started by third. If I have starting issues I pull air filter cover off and see if choke has opened, if it has I close it and crank and it will then start. Fortunately in 5 years not had any issues, but now I’ve got to replace the timing chain cover as engine started blowing oil out, and found a corrosion hole in cover, omg not easy to get at, got to remove front engine mount, fly wheel and water pump pully to access the bolts, joys of boating 😢😂😂

Linkage on the carb could be backwards so its leaving the carb open dumping the fuel in when not running. Then it floods.

I think you have something stuck in the float valve, or perhaps just need the float adjusted. I have the same engine and same carb and just rebuilt it. Getting the float just right was a chore, but I finally got it. You might check out some of the videos that Mikes Carburetors has on here.

Flooding due to either sticking float, junk float, or bad needle valve. OR a combination of all three. Easy fix if you’ve had these carbs apart before.

Definitely a float issue. Have you tried banging on the float bowl with a rubber mallet? Could just be a stuck float.

The float in the carb isnst working ither is adjuated wrong or has a hole ans isnt shutting the gas off when its full

Ever get this working? What was the solution?

I bet the dieseling is from timing being off. Rebuild the carb for the starting/running rough. It cranked a little slow like it needs a battery soon.

I have the same response as Jonathan. Mine also.has low power in water.

How you solve this issue?

your floats are sticky, and the needle valve in the carb has failed, allowing fuel to go by into the engine because of the gummy float bowls.

Did you ever find a solution? Mine has the same issue and the repair shop seems unable to resolve it. It always starts but starts very hard once warm.

It could have some vapor lock . That's why it has a little issue when you try to rerun it. But yea rebuild the carb it's like 70 $ and jut adjust your float and your air fuel mixture screw . When you start it your going to need it to be a little more rich in fuel and then after it's warm turn it down and make it a little more lean

this engine per Mercruiser is prone to Diseling when running correctly. Contact your local part dealer for the correct engine bulletin fix to correct the issue. . . They claim the issue will not harm the engine. . . .

You're dumping a bit of fuel and even thoigh the chole opened. You have to tap the throttle so the high idle cam can release.

Mine did this and it was a cracked float, changed it with a brass one.

Your float need adjusted. it is flooding engine when you shut off. I had same problem... you can smell gas when you shut off. Easy fix, just take top of carb off and bend tab on float so it sits a little lower.

your choke appears to be working properly, it's suppose to stay closed and as the engine worms up it stays open. your diesling could be cause by your timing being off or your carb might be running to lean. hope you figure it out, good luck

HEY I RECENTLY PURCHASE A 1996 3.0 MERCURISER AND IT WONT PLANE OUT CAN THE CARBURATOR CASUE THAT TO HAPPEN ??

floats are sticking and its flooding do a carb rebuild and then adjust

Merci beaucoup ❤❤❤❤❤❤

throttle pump diaphragm needs replaced

That's more than a carb problem,Time motor 2deg before top dead center, air mixture all the way in and back off 2.5 turns, start motor and advance timing till runs smooth

Your needle value is stuck open...

Did u ever use a fuel stabilizer?

dirty cab, pull cab and clean it out

stay away from alcohol fuel, for on, cause this fuel is not a carburetors friend , use non alcohol fuel recreational gas, the alcohol fuel, while the boat not in use, absorbs water, in the fuel tank, this water falls to the bottom of the tank, and also this fuel that sits in the crab bowl, will varnish, like a gluey, snot, come time for a start, this gluey substance will, clog the jets in the crab, and the engine will run crummy ,until cleaned out, never use ever use alcohol gas, only under dire straight conditions

your blower is loud af

hot bobine bad timing.

I had the

Junk.