Knissone,

This. Do you smell the oil burning in the exhaust or see it in a rainbow on the water behind the boat?

Thanks. Brad.

Oil is cheap, keep dumping it in until it no longer runs!

The bright side is you never need to do an oil change since it's all one big oil change lol

I disagree with the consensus here. I would pull it out and fix it. Rebuilding a 454 isn't rocket science and it isn't expensive. It gets expensive when it kicks a rod out the bottom because you forgot to put oil in it one day.

Sounds tired to me, but if it still performs well and is not fouling any one plug, I'd think about installing a pcv valve in one vc and a breather in the other. if that seems to help with the fumes, and assuming you are running n/a, run a little higher octane gas and keep topping off crankcase vigilantly. When I did this, I went to AutoZone and picked out a pcv valve speced for 454 truck engine and it worked great. Clearly a band aid, but it might get you down the bay a bit farther before biting the bullet on the sb 540 idea, which I'm sure would be more satisfying . Good luck.

BT

I used to run the old Merc 7.4 454 in my parasail boats and other than rebuilding the gimbal assemblies and replacing risers and after 2 years the exhaust manifolds I never had a problem with the motors over 4000 hours.

Only replaced them with a new motor package after 3 years because it was the right thing to do tax and practically wise.

I have to ad that we ran a PTO off the front dampener to run the pump for the hydraulic motor for the winch system for parasailing. That probably drew 60 hp under load and was on an electric clutch that was shut off and on constantly throughout a working day . A lot of loading and unloading on the crank and running almost wide open for 4-5 minutes at a time to get heavy flights up in the air was common on dead wind days.

Those motors took some abuse and as long as you kept the exhaust watertight and oil fresh and didn’t overheat them they were almost bullet proof.

Greatest money making motor package out there

Motors barely ever wear out in the marine world if they are a proven model. Down here in saltwater bad manifolds and risers kill most of them and right behind that lack of use and Overheating.

My buddies 79 crew cab dually with a 454 and 4sp manual had over 500 thousand when he sold it after buying it new.

My neighbor has a Eco Ford pickup with 400 thou on it and never wrenched on.

My 1997 simi truck has a million 375 on its 12.7 Cummins with no loss of power or blow by with nothing more than rebuilt heads at 900 thousand and some new main and rod bearings rolled in . One owner never Lugged never overheated and always maintained.

If you do happen to ever overheat a motor nurse it home after preventing further overheating and solve the problem than Change the oil and filter.

I know most out there knows this but just putting it out there for the OP.

I'm siding with checking your coolers. The odds of them leaking is actually fairly high being that old. And you'll never see it coming out the back because they may only significantly leak under higher oil pressure while cruising. There's also a chance it is being sucked into the intake manifold due to a bad intake gasket. Really no way to test that one though. And of course it could be sucking up through the rings. If it's that you'd have noticed a gradual increase over the years. And it'll take more years to it to get so bad you can't live with it.