boat ran outstanding for the first 2 hours then it developed a miss. pulled the plugs and cylinder number eight has massive carbon build up. it consumed about a quart of oil also. back of boat has black suit only on the side with the bad plug. plugs were new before this ride. boat sat for 2 years before i bought it last fall this was the first trip out. im going to do a comp. test tomorrow.
not sure what my next step is... thanks in advance for any input. its a 454 bored over .030 msd ignition lightning headers holly double pumper

Blow-by in # 8 . Could be a stuck oil control ring from sitting orrrr from there we get mo seriousaaaa . Do a leak down test and maybe shoot some WD penetrate in that plug hole and let er soak . Get some good oil in her . Let us know what you discover .

I would run a leak down as it sounds more like a broken ring if it is using oil and only on one cylinder.

Yup, 2+yrs old fuel. Probably hypercracking pistons,,,wallah.

Pull that carb apart too when you rebuild the motor.

I take it you are not a fan of the ultra brittle hyperutectic pistons? personally I would rather run a cast piston if it is not performance and running forged but the current trend seems to be toward hyper in most things.

Emissions.

High ring placement leaves less area for unburnt fuel / hydrocarbons to hide.

Tighter piston to wall clearances too. Less blow by because of less piston rocking.
I bored an import block once that had a piston to wall clearance spec of .000”-.0005”! I'm thinking "really? No clearance?. I finish honed to .0005" ...couldn't do zero...

i am going to do a compression test tonight i will let you guys know

Yup, unfortunately this doesn't leave much metal near the crown, and any detonation breaks the piston pretty easy

i removed all the plugs and started my compression test on cyl. #2. as the engine was being rolled over it shot some water out of cyl. #6. and one of the plugs on the other side of the engine had water/milky oil on the end of it. all cylinders were between 160 and 175 psi. except for #6 had 190 to 200 psi. assuming because it had the most water in it.cylinder #8 had the nasty build up on the plug but had good compression.the oil on the dip stick seems fine, doesn't appear to be milky at all. i am going to try and pressure check the lightning headers next. any input or tips in the next step i should take are greatly appreciated. thanks again.