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Mercruiser running a little rough

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Noticed this weekend that the boat started running a little rough at times.

Now more often then before when I first start the boat I have to give it a lot of throttle for it to start.

A few times at full throttle for the hole shot the boat would bog down and not accelerate(hesitate). But then it would pick up and take off after a few seconds.

That happened quite a few times. Also one time I turned the boat off, the motor kept turning over slowly for a couple of seconds.

Oil was changed at end of last season with winterization, along with the fuel seperator and impellor. Put 40 hours on it since. Stabil has been put in a couple of times, I just go through so much gas that I forget to put it in everytime. Thinking of changing the plugs and wires for the hell of it. Doubt they have been done.

Also I get a little exhaust smoke every now and then.

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Your carb need a rebuild. Prob $200.

Find a reputable shop as you do not want an amature messing up your carb and then have to get it done a second time.

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jdubya's got some good advice there, but it doesn't hurt to change the plugs and wires like you said. Check your timing too because that can cause dieseling also. Visually inspect the carb to make sure everything moves right and is clean.

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Have you done a basic tue up...plugs,cap,rotor,check timing etc? Check the float levels. Gas should be at the bottom of the hole. The idle and hard starting problem could be a number of things. Sounds like the idle circuit is plugged or maybe the power valve is leaking. Is it hard to start the boat after running the boat for awhile, shutting it off, letting it set for 10mins or so and then trying to restart? If so, could be a blown power valve. It sounds mostly like the idle circuit. You can try a few things without pulling the metering blocks off, but you still might have to. 1-take a can of brake/carb cleaner and blow through the air bleeds. 2- screw the air fuel mixture screws in and count the turns. Now take them all the way out and blow brake/carb cleaner through the ports and reinstall the screws the same amount of turns. You can also try holding the boat at about 3000 rpm and choking the carb off, it will suck the debri out of the circuits....sometimes that works and you won't have to pull the metering blocks off. I told Mcknight the same thing in his thread and the vacum trick solved his problem.

Edited by SBR
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Might be easier to just swap the carb out for a new Edelbrock unit.

.... I just replaced mine on a 1995 Malibu Echelon with the mercruiser 350 magnum tournament ski. After getting all parts, needles,floats jets,gaskets and the whole works, the end cost was $175 just for parts. With a big job ahead, I decided to get a new Edelbrock E1409. It's a 600 cfm Marine carb. with electric choke. I'm glad I went the new route, because after taking off the old carb. I found most of the bottom air flow valves of the carb. were rusted. Edelbrock 1409 was $340. After running it all day yesterday, i'm glad I went new. Unbolt the old, bolt on the new, connect throttle linkage and connect wires to choke. Whole job took less than an hour. The boat has never run so smooth. It idles at 840-844 in neutral, just in gear it idles at a steady 650, and I mean steady. Idled for 20-30 mins. and it only changed rpm's twice and only 2 to 648. Pulled a skier at 34 mph at 3240 rpm. It never moved more than 10 rpms the whole time. I was also amazed how quiet the motor is now compared to the old carb. That was a 9770SA Weber 4bbl. The difference in price for new carb. vs. rebuilt will probably be paid for in better fuel efficiency and more speed with less rpm's this summer especially with the way gas prices are going. Check the internet for pricing on Edelrock. Their easy to install yourself. Also, my local boat dealer wanted minimum $300 to rebuild the old carb. This new carb. runs as well as the EFI on my Vride, just doesn't have turn key start when cold. You still have to pump twice and give a little throttle till its wamed up.

Edited by ColinP
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Why are we swapping carbs on a boat that probably needs a tune up?

If the boat has not had the plugs, wires, cap, rotor, and coil changed since you have owned it that is your step #1. I would bet your carb is just fine.

Changing every part listed above is money well spent as it will keep your boat running well and are parts that should be changed as maintenance as they wear out and cause the symptoms you described. They also will cost much less than a $200 carb rebuild all together.

Edited by martinarcher
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SkiDim is a good source for rebuild parts. I would certainly recommend a tune up along with a carb rebuild. Neither are very expensive and as noted, should be part of you maintenance schedule. I would check the inside of the distributor cap for moisture/corrosion/good contact of the rotor to cap/rotor to spark plug tang gap. Your symptoms sound like clogged idle circuit/improper adjustment on choke/accelerator pump debris causing malfunction/debris in float bowls which equates to carb clean/rebuild. Also, today's fuels are blended with Ethanol and are much harder on the fuel system particularly on older boats. The station has to provide the %blend right on the pump so it's easy to check.

Edited by Woodski
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