procedure to manually flush non-running 4.3 engine?

[ShoalSurvivor]

Is there a procedure to manually flush salt water out of the engine without a running engine?
I really don't want salt water sitting in there until I can get it running!

I know I can pull the blue plugs to drain, but can I remove the hoses from the thermostat housing and force fresh water through? IF so, which ones?

thank you!

2001 Mercruiser 4.3L 225hp 4bbl Quicksilver repower

 

[ScottinAZ]

without knowing exactly what setup you have, what I would do is get to the main water inlet from the transom and hook a hose up to it directly (if needed cut the hose and put a "hose repair fitting" on the end to connect easily, just replace the hose when you recommission the engine) and flush the engine. Removing the t-stat may help get water more thoroughly through the block, heads and out the exhaust. Let it run for a while, and its likely flushed as best you can at that point. Drain block when done as with winterizing to prevent freeze damage until you get it fired up again.

 

[dubs283]

How does a non running engine with raw water cooling get salt water in the cooling system? Asking for a friend

 

[ShoalSurvivor]

How does a non running engine with raw water cooling get salt water in the cooling system? Asking for a friend

It started up in seawater for 30 seconds or so then stalled out.

I couldn’t get it started for more than a few seconds when I got home to the muffs

 

[dubs283]

It started up in seawater for 30 seconds or so then stalled out.

I couldn’t get it started for more than a few seconds when I got home to the muffs

Bummer

Not to impugn your method but a quick run on freshwater muffs isn't a bad choice for a discerning sterndrive operator prior to launch


With as many people pro and con on this forum considering salt water use I'd say you're either 100% fine or it's time to replace the entire engine/running gear and move to a location that provides decent fresh water boat operation, ymmv

 

[Lou C]

Ahhh well don’t tell my old 4.3 that. Salt water 20+ years. If you wanna flush it & it won’t run, I might consider how the water flows thru the system normally. Water enters the thermostat housing and then gets sucked into the block by the circulating pump. It passes thru the block, then the heads then exits the stat housing. So I might make up a wood disc that will fit the diameter of the big hose between the stat housing & circ pump. Drill a hole in the center of the wood disc for your garden hose. Remove the stat housing remove the stat and replace the housing. Attach the big hose to the circ pump. Put the wood disc in the end of the big hose. Stick the garden hose in the center hole in the wood disc & turn on the water. Water Should come out the thermostat housing.
Just so you know you’re worrying about nothing my engine has salt water in it 6 months each year while the boat is out on the mooring. Still haven’t rusted thru. Wanna worry about something? Guess what fresh water rots transoms much faster than nasty old salt water. Salt water pickles wood fresh water rots it .
What job would you rather do? Replace a set of manifolds & elbows? Or a transom?
I rest my case. Salt water won’t destroy a cast iron block for a LONG TIME.

 

[dubs283]

Ya dude, congrats on the longevity of your old salty. It's neat, but can confirm your situation is unique.

Simply because one old cobra 4.3 has survived (with I'm guessing constant observation/repair) does not include the other guessing between 20,000 and 37,000,000 other cobras out there.

It's cool you have an old wheezer that still putts but performance issues have changed since 1987

Take a peek at boats slipped at a local marina with salt water. Inform me of the average age of boat and how often maintenance is required

 

[Scott Danforth]

Pull hose from outdrive to t-stat housing.

Pull t-stat out of housing, replace cover

Hook hose up to t-stat housing and turn on hose

 

[ShoalSurvivor]

Bummer

Not to impugn your method but a quick run on freshwater muffs isn't a bad choice for a discerning sterndrive operator prior to launch

It ran for 10 minutes on muffs, two days in a row. no problem..
when I hit the bay, this started.

 

[ShoalSurvivor]

Just so you know you’re worrying about nothing my engine has salt water in it 6 months each year while the boat is out on the mooring.

thanks. I have replaced the exhaust manifold and elbows twice. I'm prepared to do it again. I always rinse well with salt-away to minimize the impact.

 

[Lou C]

Ya dude, congrats on the longevity of your old salty. It's neat, but can confirm your situation is unique.

Simply because one old cobra 4.3 has survived (with I'm guessing constant observation/repair) does not include the other guessing between 20,000 and 37,000,000 other cobras out there.

It's cool you have an old wheezer that still putts but performance issues have changed since 1987

Take a peek at boats slipped at a local marina with salt water. Inform me of the average age of boat and how often maintenance is required

Are you in salt water or fresh?
Before 4 stroke outboards became popular about 1/2 the boats in local harbors here were raw water cooled I/Os. So just so you understand it’s not just my experience just about all the boaters I know all had them, none were new, most 10-15 years old. As long as you changed the exhaust when needed you got 15+ years out of them.
And guess what….the preferred 4 stroke outboard lasts about the same raw water cooled in salt. Yes you don’t have to change the manifolds etc & easier to winterize. 90% of the boats in my harbor are 10-25 years old. Salt water is not death to boats & engines. If you don’t believe me I’ll take pix these boats are far from new and get used all season….

 

[dubs283]

Are you in salt water or fresh? ..........If you don’t believe me I’ll take pix these boats are far from new and get used all season….

I'm in fresh water, have been for a majority of my life/career.

I would love to see recent (2023) pics of any salt water marina/harbor that contains at least 50% 30+ year old raw water cooled engine/boats that are turn key operable

 

[Lou C]

If you're in freshwater where are you getting your info about how long raw water cooled engines last in salt?
As far as excessive maintenance/repair in salt water here's what I can tell you that I learned from 3 very good salt water mechanics and my own experience:
With an I/O you have to do what the manufacturer said, winterizing, springizing and the drive R&R yearly. Bellows last approx 10 seasons here at least on the Cobra and Volvo SX models, and these don't have the shift cable bellow failures that Mercs can
Extra maintenance over that in the manuals?
the only thing is changing the exhaust system every 5-7 years.
Want to know how many repairs I've done to the Cobra drive in 20 years?
Zero mechanical, a few seals replaced when I bought it in 2002. Trim lines replaced, 15 years ago. That's it. Original trim rams, trim & tilt pump, no repairs to transom assembly, no water leaks original Y pipe etc.
the only major repair was due to an overheat if that didn’t happen I might still be running the original heads. However judging by the cooling passages of them 6 years ago they could have rusted thru by now. So you run 20 years in salt & then put on a set of reman heads. That job cost $800 in parts.
The other extra work is bottom paint & drive paint. No way around that.
BTW there’s a mechanic over at the hull truth who’s located in the Mediterranean Sea. He has often posted that Many many I/O boats there too some with diesels survive very well. Yes it takes more maintenance. Where I draw the line is cat converter exhaust. No way I’m having an inboard boat with that heat generator bolted onto it, and $6500 parts cost to replace. IMO they are a hazard!
Salt water is not the death of boats. All the rot my boat had is from rain fresh water!
Next boat for sure will be 4 stroke outboard only because I will not under any circumstances have cat exhaust in a fiberglass boat that depends on a rubber impeller. No, No and NO!
My ultimate boat is a Steiger Craft 21 Miami with a 200 hp outboard.

 

[dubs283]

You own a Wednesday package, and that's awesome. Keep it sound and it will continue to perform until it doesn't

I've worked near the west coast and in my current area I routinely see saltys brought up from Florida (mainly) that the owner "couldn't pass up such a sweet deal" to get a boat. Many of these boats spend a majority of the first couple seasons on the trailer or in a service slip. It takes much time and patience with the right tools and information to properly repair these vessels. Aside from a complete repower including controls, wiring and associated rigging these boats never return to a reliable condition. I have a customer that only uses the axius joystick to pilot his boat because aside from replacing the entire dts system there's no clue as to where the corrosion that's causing a fault is located

It's not difficult to verify that a boat has been in salt water, even for just one season. Boats that spend their entire life in freshwater have enough issues, add salt to the equation and all bets are off ime

Still waiting on pictures of the multiple (guessing at least 2 dozen) 1993 and older boats run only in saltwater with limited maintenance that afford turnkey reliability from your harbor

I fear this thread has drifted from the main issue and expect a moderator to close it soon. That said, if you want to continue this conversation you can PM me. Otherwise, take good care of your cobra package. When they're top shape they do perform well

 

[Lou C]

I’ll get you pix but even then you can’t know if those boats, old as they look were repowered like you can with outboards. A common sight here is a 40 year old Whaler with a shiny new Merc/Yam/Zuk/Honda on the transom. Outboards seem to go 15-20 years before corrosion becomes a problem....
There’s salt, and then there’s salt. Now I’m not going to say that Long Island salt water is the same as Fla, or even S. Cal Pacific coast. Those regions may have higher salinity that what we have here, who knows. LI Sound is technically an estuary fed by the ocean, as well as the Hudson River & rivers on the southern coast of Ct, RI and Mass.
The only other things I did that some might not:
After flushing & draining fill engine & manifolds with the best PG antifreeze I could find, now I mix up my own with Sierra PG antifreeze it’s cheaper than West Marine. -100. That & spray the oil pan & timing cover with Corrosion X each fall, I think Merc recommended this in their manuals but as I’m sure you know many people do the bare minimum.
All 3 mechanics I asked had never seen a block rust thru & they were mixed on whether closed cooling was worth it on a re power. Personally I think it is…

 

[dubs283]

I think it's okay you believe engine blocks, primarily gm do not suffer from salt water destruction. I do believe this as well

That said, it's the accessories and lack of routine salt water maintenance that causes engines to fail within 5-10 seasons

Number one failure I've seen is via the exhaust system. Water intrusion to the combustion chamber will destroy an engine rather quickly, running or static

Your practice of maintenance is rare and I feel it is not a valid argument about salt water usage not being detrimental to an engine as a majority of salt water use boats get set in a slip after use with little/no inspection of fundamental propulsion systems.

The operator is quite often surprised when a catastrophic failure occurs and will often blame the manufacturer when in fact it is their own lack of pragmatism that led to the failure.

My argument is based solely on this information. I have no quarrels about any marine engine manufacturers design/quality in regards to salt water use. If the operator performs proper routine maintenance in regards to raw salt water cooled engines they will last a lifetime. Most do not as the practice often supercedes the leisure time spent using the vessel and their pocketbook will salvage any necessary repairs

 

[Lou C]

Agreed. I guess I’m a bit over the top with regular maintenance. Sometimes I felt like I was wasting money taking 6 year old exhaust manifolds to the recycling place. But never had that failure!

 

[Lou C]

 

[Lou C]

including mine here’s 6 boats moored behind my house that range in age from 25-35 years old.
When I head over to the local gas dock I could take many more prob 25-30.

 

[KM7]

I run my 92 4Winns Horizon 200 primarily in salt water in Alamitos Bay, near LA. I had been flushing it out before I left the ramp but my hose sprang a leak so lately I rinse the motor after returning home. Sometimes that is the next day if I get home late at night. How effective is rinsing the next day compared to at the ramp? Since I'm home, I could rinse with fresh water, then with Salt Away. Before all the Salt Away gets flushed out, kill the motor. That is the recommendation from Salt Away.

Any thoughts on this?

Years ago I had a Wellcraft W/ the Cobra I/O and 4.3 L that started overheating and had to replace the exhaust manifolds. I had to come up with a creative solution because the stock manifolds were either not available or very expensive. It all worked.