TOPIC: 25hp mercury

hi,i am to fix an erratic idle on a merc 25 hp ser# C173140. I have 120 pounds compression in each cylinder, it starts and runs but at idle it speeds up and then slows down and eventually stalls. Using my timing light it seems like it has good consistent spark on both cylinders, i pulled the carb and looked in the fuel bowl and cleaned the idle passage, and checked the needle valve and that seems to be working ok. I am thinking it is a fuel related problem but am not that familiar with this type of choke and fuel pump so i was wondering if anyone would have any ideas about how i should proceed.
thanks

I would agree that it sounds like a fuel system problem. First get a rebuild kit for the Carb & the fuel pump. Take note of the order that the check valves & gaskets & diaphram come out when you disassemble the pump. Be sure to get them back in in the correct order. The little pump on the side of the carb may also have a problem that I don't think comes with the kit but can be purchased separately I think only from a mercury dealer. While you at it check all of the bleed lines to be sure there are no leaks.

thanks tim, the bleed lines look good, i will start with the fuel pump, hopefully that will do the trick, by the way what does the little solenoid type thing mounted on the top of the carb do? None of my books cover these later models.
thanks

Hi,
It acts as the choke solenoid by blocking a vent hole off when energized (the plunger extends).

Regards,
Joe
www.fergusonpoolemarine.com
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