4.5L Water in Oil, Bent Valve, O2 Hydrolock

[Mwc7805]

Have a 2018 210 spx Sea Ray with a Mercruiser 4.5L 200hp. Bought used in 2021 with 200 hours on it. Put 50 hours on it. Florida salt use.
Got o2 alarms from Hydrolock threat of water coming back up exhaust since no risers on this model year. Dealer replaced o2 post, pre, post sensors again over a year. Independent mechanic said engine has major internal issues. Dealer finally got Mercury to provide 4” riser parts and Sea Ray labor after some pushing from me. O2 pre alarm occurred again months later but dealer said not related to past damage pre riser replacement. Dealer lake test drove after o2 replaced…oil alarms now, water in oil, bad compression, bent valve. Dealer saying running boat on ear muffs over 5 minutes could have overheated it, or other failed gasket, etc…not Hydrolock damage from waiting a year plus to put riser on.
At 6 years old in salt with a damaged head plus potentially more, do you try to fix head(s) with pulling them off, verifying cracked, rebuilding at thousands in costs to start?
Or
Do you replace engine with new manifolds?

Oem or aftermarket parts and engine?

Don’t want to take huge valve hit in boat to sell broken. Also don’t want to keep an I/O for Florida salt use long term.

Appreciate any help.

 

[tpenfield]

Welcome to iBoats . . .

This is the engine (right?)
.

.
CAT Exhaust and basically no riser. If it is raw water cooled (red labels) and not the SeaCore version (blue labels), then it could be early mortality of the exhaust manifolds from the salt water. But . . . they are usually a bit more robust and last more than 5 years.

If there is internal engine damage, then it would be a tear-down of the engine. These engines are Mercury's in-house build, so they are not the GM-base engines, like the older engines.

It really depends on exactly what is damaged internally. Has the dealer shared the compression #'s with you?

Got any pictures of the engine to share as confirmation (serial number would be good too)?

A quick check is a new engine is about $10,000 + installation. Not sure a tear-down would be much less, since the parts would be all Mercury.

 

[dubs283]

6 years/250 hrs is considered normal use, maybe a touch on the light side.

Running exclusively in salt water you've reached average life span of the engine. With one bent valve it's likely other valves have suffered from failing exhaust manifolds and are no longer reliable

Complete repower time, otherwise patching the initial issues leads to patching the next issue to patching the next issue, etc......

 

[MarcelSydney]

"6 years/250 hrs is considered normal use, maybe a touch on the light side.

Running exclusively in salt water you've reached average life span of the engine."

C'mon dub283.
What? How on earth could that be true. 6 years and 250hrs is the average life of an engine?
You're trying to tell us that we should be expecting to replace our engine every 6 yrs! Especially that shiny looking one in the picture with the closed cooling.
Someone forgot to tell my 23 year old engine that it should have been replaced 4x already.
Who would buy a boat if that was true....

 

[Lou C]

My engine had run in 100% raw water cooled in salt water for more than 20 years. No idea on the # of hrs. In our salt water use the blocks don’t usually rust through even after that much time but the cyl heads can get thin after that much salt use. I would up replacing the heads on mine due to overheat damage & leaky head gaskets after 15+ seasons of salt water use. The engine has run fine since that repair (2017). Total cost of top end job parts cost was $800. Heads, gaskets & head bolts. And the same time I converted from the old one piece V6 manifolds to the later 2 piece units. This was done using Barr Marine aftermarket & Volvo Penta exhaust parts to mate the 4” exit elbow to the 3.5” Y pipe. It all fit perfect & no leaks. In this case you can use different height elbows in the event that you need more height above static water line. Mine was ok with the standard height elbows. This should definitely be checked in the OP’s boat.

If you look at parts diagrams of the Merc 4.5 you’ll see that it is not an original design but a slightly modified GM 4.3. The cyl heads look slightly different than the old 4.3. Block, crank, cam, balance shaft etc all look the same. Parts cost is crazy expensive. In this case I’d want to know the cause of the failure. Were the elbows too low relative to the static water line or did the elbows rust thru or did the gasket between the 2 fail? Replacing both heads, any suspect exhaust parts will get pricey. However not 10 grand. Knowing the cause is the main thing; this engine should be good for 1500-2000 hrs even in salt water.

 

[dubs283]

6 years and 250hrs is the average life of an engine?

Yes, exclusively salt water with raw water cooling five years is average

The engine pictured is not closed cooled btw

You may get more by being very diligent with cleaning, flushing, using proper products to prevent corrosion and basically maintaining every aspect of the boat before issues arise.

Most boat owners I deal with do not have the time nor patience to be diligent with maintenance. Their boat is a toy that can be replaced, ymmv

 

[tpenfield]

The only raw water cooled engine that I ran in salt (100% of its use) lasted about 20 years and then it was toast. (with jelly)

 

[dave8311]

Dang, I better not let my 30 year old, 5.0, raw water, salt water use only engine see this post.