Mercury MCM140 with a modified Rochester Carb

[wiwrestler]

I recently purchased a 1983 four winns marquise 180 with a Merc MCM140 181 CID engine. The previous owner metioned it needed a tune up and had been in storage for the past 3 years. Before purchasing the boat ran fine on and off multiple times. Took it home and ran no problem. a few weeks later i try to start it and no luck. I decided to pull the carb because the thing was dumping large amounts of fuel into the motor, as well as leaking fuel outside the carb and everything on the carb seemed dirty, sticky and in need of a rebuild. to my surprise I found the carb has been modified in order to fit the engine bolt pattern. see attached pics. has anyone ran into this before? It looks like someone cut the outside of the bolt flange on the carb and filled it with some sort of hardened filler so the bolts could hold this carb. any guidence on which route to go is much appreciated. I plan on bringing this carb to the dealer, hopefully they might know something about this.

 

[achris]

Check to see if it's the proper carb. Might be a 'car conversion'...

 

[wiwrestler]

carb has a part number stamped in the side 17081060 which correlates with mercury number 1351-8480. but the odd thing is the Merc service manual states this carb # is for an MCM 140R ....... My motor is a 140MCM not a 140MCMR , would this be the problem? Anyone know what the proper carb for this motor should be motor serial # 6319412?

 

[achris]

By that serial number your engine is a 140R, not that it make much difference. The 'right' carb for your engine is 17081060, (1351-8480A2), so you have the right carb.. You also need to check the manifold is the right one.

Here's the table from the service manual...

 

[fishrdan]

I've been know the McGyver things, but that carb is a hatchet job...

For the fuel dumping/pouring out of the carb, there are a couple of potential causes, stuck inlet needle/seat in the carb, a sunken float, or the fuel pump is delivering too much fuel pressure. Fuel pressure should be somewhere around 3-6PSI.

Since the carb is a hack job, I would also check to make sure the engine has the correct manifold, maybe it's the correct (hacked-up) carb and wrong manifold. Rochester 2GC carbs have 2 bolt patterns and then there is the Mercarb. Your manifold could be for the bigger bolt pattern carb, and maybe someone hatcheted a small bolt pattern carb onto it... Either way, you will need to verify you have the proper manifold, and/or the proper carb for your manifold.

A rebuilt carb is going to run $250+, or you could find a decent rebuildable used carb off Ebay and rebuild it, carb kits are $25-40.

 

[wiwrestler]

Lol thanks. That's what I thought when I pulled the carb. What a hack job. Previous owner said the gas pump was recently replaced. I have some investigation to do , thanks for the insight!

 

[fishrdan]

Even if it's a new pump, I would verify that it's giving the proper output pressure. While it "should" be the proper PSI, it's a known problem that some new 3.0 fuel pumps were delivering overpressure fuel and the manufacturer's solution was to use a thicker gasket. And those were Mercruiser pumps as I remember.....

 

[achris]

Also check it's a proper marine pump. After seeing the hack job on the carb, I wouldn't trust ANYTHING on that engine (or the whole boat for that matter!)....

 

[fishrdan]

^^^ I completely agree with Chris on the possibility of an automotive fuel pump. Post up a pic of the fuel pump so we can see what's on the engine and let us know if there is any rubber fuel line between the pump and carb, or a plastic fuel filter in the system anywhere..

Off subject, also post up a pic of the alternator too, or let us know if it has "screens" on the front and back.