help - reversion on stock 454 MPI set-up?
 

I'm looking at a '97 Velocity 260 (later called 280) with a fresh 454 Mag MPI, stock Velocity thru hull exhaust, and tips in the standard Bravo configuration, I believe (see pics)

The motor was fully rebuild around the 450 hour mark. Comment on the rebuild invoice states "Water may have gotten in engine from the straight exhaust, we recommend putting flapper on external exhaust".

Motor has approximately 50 hours since rebuild. There was a tune-up (maybe 25 ish hours ago) and the receipt states "Replace plugs, cap and rotor. Rust on plugs 3,5,7. Needs new plug wires."

Rust on plugs 25 hours after a total rebuild? Yikes. Aren't cylinders 5 & 7 where you typically see reversion? The boats runs in brackish and salt, so I'm doubly concerned. I know stock Merc risers don't have much angle, but are Velocity's (of this era) with stock exhaust prone to Reversion?

If compression and/or leakdown (plus borescope?) are OK should I be concerned about reversion on this engine?

Boat is very clean, fresh motor, lots of recent receipts, and the price is right....but concerned about rust on plugs just 25 hours after a full rebuild.


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Cold be exhaust corroded and water leaking into engine. when was the last time the exhaust was replaced?

riser extension blocks prob needed - you need to do waterline testing ---- meaning freeboard to water level to bottom opening of exhaust of riser ----- per how your boat is loaded and full fuel tank. min distance needed is 15 inches

next - pressure test exhaust with air as they are on the engine.

check timing

any engine dieseling when engine is shut off

too high of an idle at engine shut off

valve overlap --- possible cam issue ??

Again it might need to install riser extensions and downward angle the thru exhaust. That is always the best option regardless on top off.

Party cove hanging out on the rear swim platform - man water reversion was common when extended swim platforms came around installed on alot of boats and everyone hung out on the platforms. Hence why you see alot of newer boats with tall risers from the marine engine OEMs.

OK thanks....I just got some new info.

The exhaust manifolds were not replaced during current owners 3 years of records....however....the same service report that stated Rust on plugs 3,5,7 also says Remove & replace both exhaust elbow gaskets with new.

Servicing Marina was not able to do a PPI today, however they were able to pull plugs 5 and 7 and report they are clean and dry. Service manager said exhaust elbow gaskets could have allowed water to leak back to cylinders, and replacement of exhaust elbow gaskets may have fixed the problem, since plugs are now clean. Does this sound plausible?

(I was not there to witness plug removal. Owner has spent lots of $$ here for storage and service. Hopefully they actually pulled plugs and statement is accurate)

I will try to observe recommendations above during sea trial today.

Cam is stock as far as we know. If I move forward with a PPI, trying to determine health of engine, given past evidence of rusty plugs (after rebuild)

- will ask if they have capability to pressure test exhaust
- check timing
- compression test, or leakdown preferred in this scenario?
- borescope helpful?
- Anything else to request (engine wise) on PPI?

If everything checks out and I move forward, sounds like taller risers, or new manifolds with taller risers would be a good investment.

and where is this boat located ? Servicing Marina ? so thats their customer boat ? get where I am going with this ?

yes, yes, and yes

owner has spent lots of $$ there for storage and service

so the boat is here in Texas ? would nt a 3 party not linked to any of this including linked to the the customer / boat / money paid / be best to have a check out ? See where I am getting at ?

yes that would certainly be the prudent thing to do...check your PM.

I would pass and no trailer in that price. rust is not good period Valves and seats prob comp in a bad way as well. Heck one can squirt some 50 w oil in the cyc and compression test can be good for that one test showing a buyer especially one a zillion miles away..

I'm going to take your advise on that. Thank you for weighing in.