the 454s in my sea ray cruiser had 1200+hours on them before rebuild but, one of them would loose oil pressure after about 10 minutes run time.ended up being a cracked crank that wiped out the center 3 main bearings.the valve guides wear and the valve leaks at the seat when they get a ton of hours and i,d bet that is what is causing the low cylinders.

The batteries were fully charged and all the plugs were out but the throttle blades were closed. Going back tomorrow with a leakdown tester and will try with a throttles open... seems very strange all cylinders are same except 5 and 6 on both motors... did it three times and numbers are same.

Those cylinders are on the back side of center riser exhaust and may see some reversion. Probably need a valve job. If taken care of and not ran hard the bottom ends may be fine.

I wouldn't bother opening the throttles. Did you notice any rpm difference last few times out last summer/fall?

I would open the throttle up maybe the number will come up a bit. Think he is looking to buy this boat.

Never thought of that but good point.

Yes I'm looking to buy.... have deposit just being thorough on inspection before sea trial.....I will do the leakdown and redo then low cylinders tomorrow with blades open. A warm motor may seal up another 10 psi. As someone mentioned, its just a cruiser and will only see 3000-3200 rpm...

True. May come up a little but with that said I'd make sure the choke isn't closed either. I've seen that lower some numbers but doubt 5 and 6 will be within 10 % of the others.

Has it always been a fresh water boat?

How much difference can you expect from the compression test being done on a cold engine vs a warm engine?

ok, whatddya mean by repower? new engines? or new rings and rod bearings? whose engines? meaning whose exhausts are on the engines? how many hours on the exhausts? my hatteras had new Indmars put in it in 92 or 93. bought it around 03 to 05 and the exhausts with 400 hours were rotted away even though manifolds had antifreeze in them. yeah mine was salt it's whole life, but lake Michigan has no corrosion inhibitors in it. I would budget for all new manifolds and risers. oh yeah; fuel tanks. still orig fiberglass tanks? if so, they gotta go. the ethanol eats the resin out of the glass and it acts like sugar in the gas tank and makes the valves stick in the guides.