Can a bad crank seal cause rough idle in a mercury outboard boat motor

Question

I have a 1982 9.8 merc that just started running rough. The motor will run but I need to manipulate the choke to keep it from stalling. I had the carb rebuilt but I still have the same problem. I was told by a few people that a bad crank seal would cause this. Any suggestions or confirmations would be appreciated. Thanks

Answer 1

Check the transfer port lines on the side of the block first.  These are rubber 1/8 lines that run from one cylinder to the other, and do deteriorate over time. Cracked and leaking lines will give the same symptoms as a bad crank seal.

Answer 2

If it is a 2-cycle engine a bad crank seal most certainly will cause the the problems you are having.

Answer 3

check your wires and plugs first

Answer 4

Yes, it's rare but it can cause rough idle etc, but the problem you discribe sounds like bigger problems than a lesking crank seal.....Has this enging been "rebuilt?  When you say the carb was rebuilt, Did an outboard mechanic rebuild it, and set the float.  Can you blow air through all of the ports in the carb, it sure soundslike something is plugged up.  When the carb was reinstslled did you use new gaskets.  Just for the heck of it, Try starting the engine, and take a can of WD40 and spray around the carb, bolck, fluwheel etc. is if the engine reacts to the spray.  Other than that, It sounds like a n old mechanic needs to take a look.. The first thing I'd do past the above is pull the head.  Good luck!

Answer 5

check the water intake for clogs, take the prop off and check make sure there is nothing rapped around the base.  

Answer 6

Make use the carb was rebuilt correctly> friend had a 20 and after it was rebuilt 3 times it had the wrong primer pump gasket in it>