Early 80's Merc 25

[dman617]

Recently refurbed an older Merc 25. All the hardware is metric so I assume it was built by Yammy or something.

Anyways, As I went through the motor, there are 2 small fuel lines going from near the reed block/intake manifold to the base of the cylinders. One line for each cylinder. What are they for?

When I run it with the lines open, it just floods out and runs like crap. Tied the lines off and runs great. I can see fuel shooting through the lines.

Thoughts?

Dman

[jrdonicht]

Are you Talking about the two fuel lines coming off the fuel pump? What year merc? Serial Number

[dman617]

5720248 is the serial. Nothing to do with the fuel pump. Basically, right under where the carb bolts to the intake manifold, then the lines run what looks to be the base of the cylinders.
It's an 1980-81.

[jrdonicht]

Are you talking about Part 3&4? I Not sure on this one. http://www.boats.net/parts/search/Me...VER/parts.html

[staylor]

I had three of them and other than the Mikuni Carb and the wimpy recoil starter bolts they were a great engine- you shear the starter bolts from cranking the engine too many times when the carb needs a rebuild.

The lines you are looking at are the crankcase bleed lines- they are supposed to carry excess puddled fuel in the crankcase back to the reed block and into the reed cage for "digestion". They should not have fuel in them at all times, and mostly function during trolling.

These often act up when the carb and built in fuel pump and built-in primer body are in need of a rebuild kit. They can also act up when the rubber seal inside the reed cage is ruptured during an overhaul, or the line is not firmly connected to the reed block.

If you haven't already done so- I would rebuild the carb first with a complete kit- they need your s/n for this since Merc used several variations on the type WMK and WMC carbs- and I believe that very early "semi-Yamma-Merc" 25's used Tillotson carbs It also helps to take your entire carb into the dealer and he may just look and say "Oh-that one". When you get the kit- make very sure you get the "final" design primer actuator rod- which is colored in bright blue plastic- vs the white plastic rod that is probably on your engine. The white ones were prone to cause all kinds of problems- including the one you describe- with fuel in all the wrong places.

The last Merc 25 two stoke I had was one of the best little engines I ever had- after they had upgraded the carb a few times. I then switched to the 15 Yamma-Merc 2 stroke, and these had their own weird carb problems with the Mikuni carbs....ahhh...for the good old days of Tillotson and Carter and Mercarb carbs on Mercs.

[jrdonicht]

Great Information Staylor!!!