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Mariner 8 HP loses power when pushing the gas

V

Vincent

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" I bought a secondhand Marine

" I bought a secondhand Mariner 8 HP of 1989. The motor has several problems. First it starts very difficult when the engine is cold. I replaced the spark plugs, but that didn't fixed the problem. Second when the motor is running and I push the gas, the motor loses power and falls off.
When starting again (that goes easy now) bulk of smoke is coming from the motor (like puff puff). I also noticed that the new spark plugs turned grey and were greasy. Can somebody explain to me what the problem is and if this is repairable.

Thanks,
Vincent (Amsterdam, Netherlands) "
 
"which plugs are u using???

"which plugs are u using???

also those carbs seem to be TOUCHY as they age, I Own a merc 8hp the same yesr and it has had some of the same malfunctions you are describing I should be able to answer with a little more info,


basic setup ( how i set mine up)

Start and let warm up a little, adjust idle mix untill highest rpm at idle is attained and then adjust JUST A HAIR(ablut 1/32nd turn rich to prevent lean condition). now there is a base idle mix, start advancing throttle to mid rpms, it should be smooth and with only a minimal ammount of exhaust smoke, if that is the case shut off and alow to cool (overnight is best so you can test coldstart).

To start cold, pull choke knob out 3times, leaving it out the 3rd time, start engine using quick reps if it is pull start, should fire on 1-3rd pull, once it fires immediatly push in choke, put in gear and go.

the plug you should be using is NGK BP7HS-10 if it is used as a kicker and idles alot due to the fact that the factory BP8HS-N-10 is to cold and suseptiple to FOWLING the BP7HS-10 is 1 heatrange hotter and huns a very nice Dark Caramel color in every engine i have worked on and a very light caramel color in mine, (i run my engine a lot leaner than most people.

It sounds like you are just running WAY rich and in need of adjustment.

also besure you are using a good quality gasoline with atleast 87 octaine(US) 92(euro) and a TCW-3 Quality 2 Stroke Engine Oil mixed 50:1 gas to oil
low quality oil causes excess smoke and runability problems.

That engine is definatly repairable and you can do it yourself as long as you know how to work a screwdriver and have the patience to listen to suttle changes in engine RPM and Exhaust tone

The 2 things that go wrong with that engine are CARBS and CARBS!!!!! that engine has proven to be one of the most reliable little engines merc has made.


my little engine has 50 lbs of compression as it has about 6500 hrs of operation on it and it is tired yes but it has never failed to start and is as reliable as they come. every mechanic says ut shouldnt run , not only does it run, it runs better than new, it dyno'd out at 9.1 hp @5200RPM last year when the Mercury rep was demoing a engine dyno. a 2002 8hp only made 8.8 hp@5000 RPM


anyway hope that helped and good luck

nick"
 
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