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Selva 50hp outboard boat engine is miss firing

Started engine 50 selva four stroke up this year and was getting a miss firer called out a mobile marine Macanic out we drain all the fuel tank and drained carberetors and put new spark plugs in and still the same he suggested we take carberetors off and clean them which he did bit better he then said give it a run on the water took it out runs fine at 2500 revs the go faster and it just splutter and don't want to go any faster it runs fine at 25000 revs any help out there please?

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Posted on Jan 02, 2017


SOURCE: Lawn mower engine runs rough and puts out white smoke

Pull the carburetor and clean it for staters.Be sure to change oil any little bit of moisture in the crankcase will let it smoke white by seeping by the valves and piston rings.Also put a little small amount of dry gas in the gas tank to rid all of the water that may have been left in the tank. I some of this will help you.

Posted on Mar 19, 2009

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SOURCE: Briggs & Stratton engine on Murray lawn mower

I always replace the air filter if its a paper element, and even if its a foam element I replace it rather than clean it. That said, engine stumbling is rarely and air flow problem - but it could be, so having a new filter assures no air restrictions.

I would drop the carbuerator bowl. On the bottom of the carb, near where the fuel line comes into the engine, should be a nut. Removing this nut allows the bowl to drop off the carb. Some engines the bowl screws off, you will have to look at the bowl. Often the bowl has sediment or sludge buildup inside. Cleaning the bottom of the bowl can prevent that sludge/sediment from plugging the intake tube. Even on newer mower models this is a common problem, the gas line tubing interior breaks down and the inside of the tubing can start degrading - ending up in the bowl as sludge.

After cleaning the bowl, I would add one ounce of fuel line cleaner to a full tank of fuel and run the entire tank of fuel. This will clean any deposits or "varnish" from the interior carb parts. Doing this and the first step will assure your carb is clean and functioning.

If that doesn't help, then I would look at the spacing between the magneto and coil assembly. If you want to do that I'd like you to write down all the model numbers and serial numbers on the engine nameplate, that way I can give you specific directions.

Hope this helps,

Posted on Mar 29, 2009

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SOURCE: Have a Briggs & Stratton lawn mower engine, 4.5

Is Blade new or causeing vibration .Chge blade,

Please rate Thank you jj505

Posted on Mar 30, 2009

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SOURCE: 1996 Mercury 150 Nitro EFI

Dont have the manual in front of me...recollect that there's two types of warnings. The pulsating warning is oil (starts with 30 minutes of oil left) or the fuel filter (or sperator, something like that) may have water in it. Running outboard with cover off, is a little black box that would have a red light lit if that's the case. If oil full & no red light, may be oil injection system...would also check to make sure lines aren't pinched, etc. Mine has been specific to oil the two times its gone off.

The full non-pulsating is engine overheat. Not sure beyond that.

Not much, but hopefully gets you going.

Posted on Jun 23, 2009

  • 155 Answers

SOURCE: Mower stutters when i turn up to full throttle.

Hi if it is older than 2 years it will need a new diaphram and gasket under carby you will also need to clean out the fuel bowl in the top of the tank this should fix your problem.

Posted on Jul 25, 2009

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50hp Mercury outboard electrical schematic

Hey David,
Yo should find all the info you need here..this will be very very helpful...' Mercury Outboard Manuals by Seloc 1965 2014

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1998 1150412UD Mercury Outboard - is it 2 or 4 stroke

If it has an oil compartment, it has to be a two stroke. There is a rough and ready way to check. A four stroke engine has a compression stroke on every four strokes, whereas a two stroke has compression stroke on EVERY upward stroke of the piston. Remove the spark plugs, and turn the engine until you see the piston. Put your finger over the plug hole and turn the engine one revolution. Do you get compression? Keep turning, do you get suction and then compression again. If so it is a two stroke.

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need the year of manufacture as some 2 stroke units have oil injection that automatically mixes the oil in the correct ratio for engine rpms otherwise it is 50:1 ( 50 parts fuel to 1 part oil)
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google --type in mercury outboard oil to fuel ratio

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Matt, If engine is two stroke and not oil injected then yes you must mix 2 stroke oil and fuel. 4 stroke engine have a crank case which is filled to proper level with 4 stroke engine oil. Check the attached links,instruction and guides, Good luck
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