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need help 1990 Mercury 75hp runs rough after cleaning fuel tank and line, changing spark plugs ect

M

mercury75hp

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Hi, I need some help with my 1990 Mercury 75hp, it runs rough and smokes even after cleaning fuel tank and fuel line, and changing spark plugs ect. Also there's a lot of gray oil or grease coming out of the lower unit along with the smoke. It won't won't idle at all and trys to race itself up and down in speed when I have it running on the hose. I have a video and some pics of the gray oil. Here is a link to video of the motor running https://www.dropbox.com/s/qd435ytkntpfltm/20190216_130535.mp4?dl=0 And here is the pic of the oil,
20190216_130420-small.jpg20190216_130351small.jpg
 
What was in the fuel filter, lines and tank.....old rotten fuel? How long was it stored unused? Maybe gonna have to clean up the carbs, running rich. Also, I have a similar Merc 115 here that perhaps by design seems to over-inject oil. It has been my main ride for 12 years now. I avoid any unnecessary idling. I do use Amsoil Injector Oil and that minimizes the smoke. Seems your motor is "loaded up" and sick from rotten fuel and excessive oil. Also, do a spark jump test. Should get almost half inch snappy, lightning-like spark. What is your compression on each cylinder too? That will give us an overall health assessment of that old girl.
 
faztbullet said:
Fuel pump diaphragm damaged......
Click to expand...
Dang, how do I figure that out? Is that going to be a tough thing or can I take it off and replace it? Is there a diagram somewhere online? Thanks.


edit: I just found a kit on this site: 42909A 4 - Diaphragm Kit, I think this is what I need??
 
Last edited:
Primer bulb must go hard.-----If it does not then fuel is going somewhere.-----Either through the float valves or a hole in the diaphragm.----Simply test.-----Repair kits for fuel pumps are an easy fix.
 
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