1985 7.5 rebuild case seal question

I am reassembling a1985 7.5 hp after changing rings due to running hot.
on dissembling it appears that there is no sealant used between the two crankcase halves
Is this correct or should I use some kind of sealant?
Is there any specific prep for the two block halves needed to assure a good seal?
The surfaces appear polished and fit together very well but I am concerned about leaking
thanks

Facts for you.--------This is a precision " metal to metal " joint.-----It has to be to properly clamp the reed block and bearings.-----A sealer was used.-----So make sure you scrape it all off.------Since it is a metal top metal joint MOST if not all the sealer squeezes out.----You will find that it had a very thin coating of sealer as in less than 0.001" .-----Make sure this joint is absolutely clean and free of any bumps and burrs.-----Use the proper sealer ( no filler content ) and Loctite 518 is one sealer you can use.

Right on, Racer. Use your finger to spread the Loctite very sparingly but evenly.

???-----You use a 1/8" bead of sealer.------And no I do NOT spread it around with my finger !

Okay. Not one failure for me in 52 years. Starting long before Loctite 518 was even conceived. But what do I really know? Only what works for ME! Like I said before, my advice is out there for those that want to use it. The choice is theirs. You and I may use different techniques, but the ultimate goal is to repair the motor and I stand behind my work with a 1 year warranty.

From what I've seen, those particular Mercs need crankcase sealant far more that larger ones. I've actually witnessed smoke leaking out between the joints when one of them backfired a few times.

You'd be surprised at what internal forces are involved when a backfire occurs inside the crankcase. Lots of surface area there. Larger displacement Merc have proportionally far more and larger bolts holding the crankcase together.

Jeff

I need some help,
After running my 7.5 hp with a failed water pump, I did compression test and got about 45 psi, review of other posts from this forum suggesting that I overheated and required new rings from loss of temper.
i rebuilt the engine replacing rings and honing cylinders.
old rings appeared fine.
My issue is that post rebuild appears to have compression only a couple PSI greater than before, maybe 48 psi.
i haven’t run the motor yet, all readings cold motor in my shop using a harbor freight tester. I crudely calibrated the gauge by putting the blow nozzle from my compressor on the end and get close to tank pressure.
The motor ran ok but didn’t idle very well and lower plug fouled some.
Thanks

Were pistons scored ??-----Perhaps a better gauge is in your future.-----Plugs do not foul without a reason.------Test for spark that jumps a gap of 3/8" on both leads , on a proper test device.----I say perhaps the motor was running on one cylinder.-----Any other trouble shooting done ?------Checked the plastic cam follower on top of carburetor ?

Probably will see improved compression once it's run awhile. Did it idle well before the overheating?

That's horribly low compression.

Jeff

That is low compression.-----Due to a bad gauge.----Poor technique.----Motor that is junk.-----Hard to explain this to a novice sometimes.