1988 Merc 115 Inline 6 - idle problems, WMK-41 & 39 carbs difference

adtodd

Recruit
Joined
May 4, 2013
Messages
3
1988 Mercury 115 Inline 6 with "enricher" choke system
S/N: OB371181 Model: 1115452BD
Top & bottom carbs: WMK-41
Middle carb: WMK-39 ???

I'm new to this forum and have read with great interest concerning these inline 6 motors. I can appreciate the knowledge and experience shared here. Hopefully, some of you can offer information to help me.

I'm having idling issues with my motor, and this is a bit concerning when fishing in the Gulf Coast bays with tides and currents. The motor runs pretty well at faster speeds, but won't idle well. It begins to stall, and can be hard to restart and keep running. It seems like the motor begins starving for fuel at idle. The motor did set up through the winter without draining the carbs or any other storage prep. I am running ethanol-free premium gas and Walmart 2-stroke oil.

I've changed the fuel pump and fuel hose/primer bulb coming from the built-in tank, but that hasn't resolved the issue. After reading some of the posts here, I thought I would clean the carbs. When I removed them, I noticed that the top and bottom carbs were WMK-41's (41-1B1408 and 41-3B0918 stamped on the sides), but the middle carb is a WMK-39. My first question is what is the functional difference between the 41 and the 39? I would imagine these all need to be the same. The floats are not filled with fuel, but I haven't checked anything else on the carbs yet.

After I pulled the carbs off, I did see that the hose from the enricher valve was split where it attaches to the barbed fitting on the motor just left of the middle carb. This could certainly be a fuel or air leak point, but would that affect the low-speed operation? I do plan to replace all of the fuel lines and the spark plugs (NGK BUZHW #2147).

Any thoughts or suggestions would be most appreciated to help me step through this effort in the right order.

Thanks!
Andy
 
Top