1990 Mercury 90 HP fuel problem...I think.

[apeltim]

In storage two years...ran fine before. I tried to start the motor using the old gas w/o stabilizer. Engine started fine, idled for a few seconds and slowly quit like it was being fuel starved. I tried several more times, increasing the throttle each time. The engine will accelerate and keep running around 2000 RPM...but doesn?t sound right...sounds like its running on two cylinders. Furthermore, if I leave the engine running
at 1500 ? 2000 RPM without adjusting the throttle or engaging the choke, it gradually begins to lose RPM and dies.

I assumed it was the old gas, so I emptied the tank and put in five gallons of new fuel. Same problem occurs. I found that if I play with the choke, I can keep the engine running at idle. A second of choke in two or three second intervals keeps it idling. Similarly, when running at 2000 RPM, a second or two of choke produces another 1000 RPMs and the engine seems to be firing on all three cylinders. If I keep the choke engaged for more than about three seconds the engine abruptly dies.

I checked fuel lines and bulb...seems okay. Spark plugs look good. I can also see the fuel running through the clear plastic filter during engine operation. Finally, I have a 9.9 aux motor that runs fine using the same boat fuel system that is supplying the 90HP Mercury.

Any suggestions appreciated...

Thanks!

 

[dbrew]

Re: 1990 Mercury 90 HP fuel problem...I think.

i would pull the carbs some of the bad gas is clogging up the orfaces thats why it runs bad, it is only letting some fuel in the engine. if you dont know what you are doing take it to a shop it probubly wont cost that mutch, i usually get around 100$ if i take them off and do a test run.

 

[Dave1027]

Re: 1990 Mercury 90 HP fuel problem...I think.

Try this before pulling the carbs. Start the engine and have someone squeezing the primer bulb. If if keeps running then you have a fuel delivery problem like a restriction or fuel pump or filter.

It may just be water in the gas and it's in the carburetor bowls. May have to either drain the carbs (usually a plug on the lower side) or keeping running it till the fresh gas has completely replaced the old.

 

[apeltim]

Re: 1990 Mercury 90 HP fuel problem...I think.

Thanks for tips. I'll drain the carb bowls and pull and check all filters and lines...barring that, I'll rebuild the carbs. Thanks again...