I've noticed what appears to be a little splashing/whipping of oil under my port 1994 454 mag, just behind the harmonic balancer is I believe where it's coming from. I notice in this link part 26 is an oil seal. What's involved with changing this out? I'll need a puller for the balancer, what after that? Is this oil seal my problem?

http://www.mercruiserparts.com/Show_...ND+FRONT+COVER

Maybe a seal puller, but that's about it. It may also be necessary to have an impact gun to get the balancer bolt loose when you start. Pop the new seal in and torque the bal bolt to spec.

Seal puller works if you have one, If not a wood screw and some channel locks work great. 15 minute job tops.

WAIT. If the seal is leaking the more than likely the balancer has a groove cut in it from the seal. There are balancer repair kits to cover the groove then put it back on. It would also be helpful to use a balancer puller/Install tool.

should also have a balancer puller and installer

Yep, the installer is a must have. NEVER beat a balancer on, you will destroy the thrust bearing that seats crankshaft endplay. You should also never use the bolt to suck it in becuase you can rip the threads out of the crank that way. It's an easy job just make sure you have the right tools.

Posts #4,5 and 6 have it right in my opinion. Another catastrophic negative to pounding the balancer on is that you could break the elastomer bond between the inner and outer ring of the balancer. They have been known to come apart or crack and come apart.That's bad enough in a race car, but that shrapnel going through the bottom of a boat would not be pretty. Use the installer to put the balancer back on. Some folks have used a high quality,longer than stock bolt to pull the looser balancers on but it's not recommended.The stock bolt is too short to do this without stripping some threads. In a prior life when I'd have these things apart frequently, you could very carefully hone out the ID of the balancer to give less of an interference fit. Safety wire the bolt and a little Loctite and it was a snap to get this stuff apart. Just another opinion...

Thanks everyone!!! Think I'm good to go...

Just going to add this to my winter project list which is continually growing.... Present project is to finish my new garage and get the boat under cover!!!

May also be seeping past the keyway slot

US1 Fountain makes a good point. Its hard to tell from post #1 exactly how aggressive the leak is, but the keyways do weep. Lots of folks put a dab of sealant on them. It's worth a try.