rollercoaster
Contributing Member
1993 Mercury 4 cyl. bottom carb blowing out gas. Cylinders has compression and spark. Engine run on top 2 cylinders.
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Well put and dead on as always...jbSame motor that wouldn't fire on 3 and 4?
Gas blowing out the throat is almost always busted reeds (which would have also accounted for 3 and 4 not firing) - that really sucks on this model - have to split the block....
And cylinder compression has nothing to do with the crankcase - so yes, can have 125 lbs at the (head) and a big "hole" in the crankcase....
Is there a guide available to help me replace the reed valve?Well put and dead on as always...jb
Ps, if you keep cranking on it you won't have compression in 3-4 for much longer.
Yes, definately need, at minimum, a Seloc's manual but would be better off with a Merc factory manual (even though it's about 80 bucks compared to the $35 for Selocs).
And as Jeff notes, you don't have to completely pull the crankshaft out to get at the combination main bearing/reed cage, but there is a ton of stuff you do have to remove (including the flywheel, a good chunk of the ignition system, linkages etc, plus anything in the way of the crankcase bolts).
So alot of work on many different components just to get at one relatively small/easy to fix problem.
You will also need to replace any seal or gasket you disturb in the process (which is where the factory manual is superior in identifying, by part number, everything you have to touch or replace).
This is not a little job but it's not rocket science either. And if you are thinking "maybe a shop should do this", you can get some quotes but if you hear numbers approaching the 1000 dollar range that wouldn't be surprising...
And if ultimately you find that the lower reeds are stuck, the cause of that "came through the carb" in the first place - so "just because" I would clean and rebuild the carbs - otherwise you could be doing it and another reed job in the not so distant future...