help 1972 merc

[safari12]

help 1972 merc

i have a 1972 650 merc thunderbolt ignition it wont idle and under load it just bogs out on wot, rebuilt carbs adjusted them while under load still no change the compression was#1-100psi,#2-120psi,#3115psi .I put in all new plugs and i pulled them after running the motor the top two had a little bit of oil residual on them but the bottom one is clean as it was out of the package is this water fouling the bottom plug, i am stumped if this is the problem is this motor fixable the serial #7003766.also ipulled the plugs and grounded them they were all firing good spark

 

[WillyBWright]

Re: help 1972 merc

Re: help 1972 merc

Welcome to iboats.<br /><br />Chances are your bottom crank seal is bad. Could be the bearing is bad too. I think you have to split the case to get either top or bottom end caps off, but I'm not sure. I know they fit awfully tight. Could also be reeds. That would definately require splitting the case.

 

[emckelvy]

Re: help 1972 merc

Re: help 1972 merc

You can pull the end caps off without splitting the case, if you're careful to use a proper puller and not try to pry them off the block. There are threaded holes in at least the bottom cap for this purpose, and you could use the stator mounting holes in the top cap for that purpose.<br /><br />Also possible it could be a leaking exhaust plate but with only the bottom plug wet chances are it's the seals. If the bottom of the crank is eaten away in the sealing surface area, you can get a speedi-sleeve assy from Mercury to tap over the rusted portion to provide a new seal surface.<br /><br />HTH............ed