mercury 850 outboard blue band not sure of the year

[SGT.James]

like some of the other people here I have having trouble throttling up. it will idle fine and even when I use the rabitt ears in the yard it will trottle fine but once in the water it will idle fine but once i hit the throttle it sputters if I dont back off it will sputter and die. but I notcied if I pump the primer ball it will run fine but after a while it will start slowing down then die any Ideas this is my first boat I have no clue

 

[dwco5051]

Re: mercury 850 outboard blue band not sure of the year

Sounds a whole lot like the fuel pump. A easy fix on these 850's. Locate your serial # and it will be an easy search for the right pump kit. The filter screen is right under the fuel pump cover and it is possible that it is just clogged also. Don't run it hard till you find out what is causing the fuel starvation. The top one or two cylinders will be the ones that will run lean with a weak pump leading to piston damage.

 

[CharlieB]

Re: mercury 850 outboard blue band not sure of the year

Ditto the fuel pump, test by disconnecting the fuel line after the pump, crank the motor and observe the fuel, you expect a strong pulsed stream. Temporarily install a clear hose between the pump and carbs, observe the fuel while running for ANY air bubbles indicating air sucking into the system from a loose/cracked hose or fitting.

Bogging when the throttle is initially opened may also be a sign of too lean an idle mixture. If the carbs have recently been cleaned the idle may not have been adjusted quite rich enough. If no recent cleaning then it may be the mineral accumulation over time is now enough to notice and the carbs now need cleaning.

 

[SGT.James]

Re: mercury 850 outboard blue band not sure of the year

thanks for the info does anyone know were i can get a free pdf manul for a 1975 mercuy outboard 85hp the link I found on here didnt have my motor in it or the SN didnt match

 

[dwco5051]

Re: mercury 850 outboard blue band not sure of the year

I have one in front of me now (not for sale) which covers the 1975 and 76 models. The number of the factory manual is c-90-755512. I just did a quick search on Amazon and found one for $28.

 

[merc850]

Re: mercury 850 outboard blue band not sure of the year

There is a screen in each carb and they might be clogged. It happened to me - same motor same year.

 

[dwco5051]

Re: mercury 850 outboard blue band not sure of the year

Ditto the fuel pump, test by disconnecting the fuel line after the pump, crank the motor and observe the fuel, you expect a strong pulsed stream. Temporarily install a clear hose between the pump and carbs, observe the fuel while running for ANY air bubbles indicating air sucking into the system from a loose/cracked hose or fitting.

With the engine not running pump the bulb up while observing the fuel pump for leaking fuel. These pumps will leak around the edge of the fuel pump cover if the gasket is bad. Also look for cracks in the pump cover. I have seen covers cracked from overnighting to try and stop a leak from a bad gasket. Either of these conditions could cause it to suck air and interfere with the fuel delivery.

 

[SGT.James]

Re: mercury 850 outboard blue band not sure of the year

that is cheap but I lost my job in OTC so was looking for free. to cut some cost.but thanks ill have to buy one after I get a job