Mercury 9.8 problem

Picked up a nice looking 1976 9.8 model 110 cheap the other day to use as a kicker on my 16' Lund. Owner said it started and idled but died when you reved it up. Took it to an experienced mechanic who has worked on many 9.8's and he spent hours trying to get it going right but finally called me the other day and said he had to give up on it. He checked it over and said compression was good and cylinders looked fine but one coil was bad so he replaced it. He cleaned and checked the carb and everything there seemed fine. It has spark to both plugs now but only the top cylinder has combustion. It will idle with the bottom plug disconnected but not with the top plug off. He tried every trick he could think of to get the bottom cylinder to fire but no luck. He said he has heard of this problem before from other mechanics and the opinion is the crankcase seal leaks causing the cylinder to fail to fire. I didn't understand his explanation so I hope I'm saying this right but I may have misunderstood him. In order to check that he would have to pull the powerhead which would cost more than the motor was worth. I'm no mechanic so I hope I have explained what he told me correctly. Does anybody here have an idea what is causing this problem and how it could be fixed? Thanks for any advice.

Bottom crank seals need replacing.

"Experienced mechanic"?


JEff

Is this difficult and expensive?