Mercury 9.9 2 stroke water entering bottom cylinder

[Bluestream]

I have a 89 Merc 9.9 (not a Yamaha) That runs rough at idle and higher speeds. Lower plug always looks wet/grey emulsion and often small water droplets on

Compression good at 105 PSI in both, gas is fresh and 50:1
New plugs installed, both getting good spark. (has aftermarket CDI box)
Carb (has carb from an 8HP) was taken apart and was clean. Fuel needle/seat held pressure for 10 min, float set to 1 inch
Reeds appeared to be good and sealed tight
Float was good and main jet clean
Low speed jet at 11/4 turns out

Is there any way for water from cooling system to enter the cylinder? When I bough the motor, the impeller was shot, so it may have been overheated at one time...

 

[racerone]

Bottom seal on the crankshaft and exhaust cover gaskets need inspection.-----Pull exhaust cover first and have a look there.----Inspect pistons and rings with covver off.

 

[Bluestream]

I will have a look at the exhaust cover and report back..Are you referring to the powerhead gasket, or crankshaft seal when you say "bottom seal on crankshaft"?

 

[racerone]

I believe I mention SEAL and did not mention gasket !

 

[Bluestream]

You did, Im having trouble visualising how a crank seal is exposed to water flow, and could ingest water....

 

[Bluestream]

Had a look at exhaust cover gaskets and they seem fine. Cant post pics on this site for some reason, but will post some from external host.

Pistons and rings look to be in VERY good condition. I guess next step is to pull the powerhead??

 

[Bluestream]

Hopfully these pics show up...

 

[Bluestream]

anyone out there familiar with these 9.9's?

 

[racerone]

I own a number of them.---Last 2 ( nice looking ) were picked up for repair and were missing lower units.---Lower units are considered a weak link on these motors.-----Many shops are good at selling new motors when it looks like the labour / parts cost approaches 1/2 of a new motor.----These 2 are an easy fix for me.

 

[Bluestream]

Yes, I see a lot for sale needing lower units...Any change I just need a power head gasket? I guess at this point it doesn't matter, just pull it and see...

 

[Bluestream]

Update: I replaced the exhaust cover gaskets, just for fun and no change. Removed power head to look at the seal, and when I look in the PTO shaft hole, I can see in and the the crankshaft / connecting rod moving. Must have a hollow crankshaft at the output, splines for the drive shaft to mate with. How these engines ever seal pressure is beyond me. And how water can get in past the worn seal is also beyond me as the area is not exposed to water.

Anyway, any tips or threads on how the replace the lower seal? It looks like there is a plate on bottom of the case, but it does not want to move.

Any thoughts are appreciated...

 

[Bluestream]

Removed base plate and base gasket appeared fine. Dealer says he doubts its a lower seal. Any other ways water can be entering lower cylinder?