Logo
FULL SITE MENU

Help with carb problems

B

barnfinder75

New member
"first of all this is on a 198

"first of all this is on a 1985-86 mariner 45hp 4 cyl. i bought this motor that had been sitting for some time but had been stored dry. put fresh gas/oil through it and it ran perfect. i went ahead and purchased 2 carb kits for it (the ones that have the rubber and cork parts only, not any hard parts) and installed them. everything in the carbs looked in good shape aside for some mild discoloration from old gas in some spots. it ran perfect at home but once in the water it starves out after about 5-10 seconds at full throttle. i think it is just the one part i didn't clean - the needle and seat in the bowls- i just need a second better opinion on what else this might be. i tried adjusting the mixture screw but all that does is over richen the engine till it dies out. by the by these are the walbro carbs with the fuel pumps on the sides, they have new diaphrams and clean screens too.HELP!!"
 
"you need to be 100% certain t

"you need to be 100% certain the main jets are clean, no fuel means no oil. If one carb is bad then 2 cylinders go without oil. We always start with spark and compression test so we know the engine is worth fixing. Next change the waterpump so we don't cook a good engine. Once running try pumping the fuel bulb, if it helps the fuel pump is more than likely bad, but it could be sucking air from any of the lines. The mixture screw only changes the idle mixture, in for lean out for rich, normal starting position about 1 1/2 turns out."
 
"it has 120-130 psi in all fou

"it has 120-130 psi in all four cylinders, it has a new water pump, the fuel pumps have new guts and the motor runs well when it isn't in the water, when we are in the water trying to open it up, or even slow running, pumping the primer bulb does not affect the running of the engine. i also pulled the main jets and they seem to be very clean with no obstructions. i understand about when the engine runs lean you get no lubrication, does running it out of gas at the end of the day damage to motor as well?"
 
"well i figured out what it wa

"well i figured out what it was, the fuel line coming into the fuel filter runs under the bottom carb, when you put it in gear the selector laver was pinching the line shut between the bowl and the lever, rerouted it around it and it runs perfect. any answer on the running out of fuel at the end of the day?"
 
I would add 1 note to all the

I would add 1 note to all the great advice above. In some situations you DON'T want to run out the gas.

On certain models with multi-carb set-up's the gas is fed to the top carb and then piggy-backed to the lower carbs from the top carbs bowl.

In such a case the top carb will run out of gas before the lower carbs (it's bowl may drain while the lower carbs still have relatively full bowls).

In that situation the lower cylinders will still be forcing the pistions fed by the top carb as they continue to fire while the top cylinders keep running without any oil/gas causing excess wear and possibly shortening their life....
 
"Thanks Graham, I'm learni

"Thanks Graham, I'm learning something new every day,hopefully something will catch in the gray matter,whats left of it, after all that beer I took to my beloved merc800
lol.gif
"
 
Back
Top