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engine flushing - FWC engine

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bobct

Advanced Contributor
I added Groco adapters my seacocks which allow me to easily do a fresh water flush to the raw water side of the system. I always do it at the end of a weekend where the boat is likely to sit until the end of the week. If I go out on consecutive days, I might skip it.

Does anyone else do this and does it make a difference in how long the risers/elbows last? It seems like the right thing to do but might be a waste of time. The heat exchangers are original (22 years) and the U coolers are new.

What do you guys think?

Bob
 
don't do it here and haven't had any issues. That said, we have s/s merc elbows and merc HX installed - OEM oil coolers.

It sure isn't a waste of time as it won't hurt anything....efficient use of that time is another thread's topic.
 
Mark,

Are those elbows mounted on the older log style manifolds or the center mount riser type....I might l;ike to try that
 
Al:

We switched over to the merc center riser manifolds/SS elbows when the first issue with the old log style elbow arose. We got the whole merc setup cheaper than just the log style risers & elbows. Probably saved 100#, too. another benefit was 4" hose vs the 3" on the log styled stuff. Sadly, you will have a hard time finding those elbows as they haven't been made for a long time. My understanding was the foundry merc got to make them wasn't making a profit so they wanted a price increase on the 'next contract'. merc (brunswick at the time, i think) balked and the s/s product died almost as fast as it was born....They are sweet as we haven't had to clean them since their original installation.
 
My experiments have shown that fresh water flushing does not improve the life significantly of the cast iron elbows. Good for 4 years flushed or not. However, I do think that the flushing helps avoid scaling of the heat exchanger, so I still do it.
 
Do you need to regulate intake water pressure down to a level that is what the boats system is build for? The pressure at my marina is 50 psi.

I remember that being a possible cause mentioned by a boat mechanic when a raw cooled system showed signs of water in oil. Gaskets breaching from higher psi then rated. Never found reason and boat was sold.
 
The Groco valve has a shutoff so I only open it about 1/2 way. I can see the water level stays about 1/2" from the top of the strainer so I know it's not too high. The 1st time I used it, I opened it all the way and water came out of the strainer cap so I knew it was too high.

I'm on my second year with riser/elbows. If you guys want to wait around for a couple of years, maybe I'll keep flushing and report back on how they look in 2013 :)

Bob
 
slauder said:
Do you need to regulate intake water pressure down to a level that is what the boats system is build for? The pressure at my marina is 50 psi.
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Bob, slauder poses a good question, although I must use theory over practical experience in order to comment on this.
I know that practical experience is much more valuable.... but bare with me! :D

A couple of things that I've learned over the years about this.
Salt Water corrosion (rust or Iron Oxide) is very difficult to arrest once the process has begun.
You may have even heard the phrase; "Salt Water corrosion never sleeps!"

A fresh water flush may not accomplish what some of the Neutralizing systems will accomplish.
I've not used any, but there is one kit called Salt-A-Way, whereby a Neutralizing chemical is introduced into the potable water that's used for the "flush". In fact, this system can apparently be used with Salt Water.
When introduced, it chemically changes and/or reduces the corrosive characteristics of salt water.
How well or how much.... I don't know! But the claim is that it works.

IMO, there's the caveat to these systems (depending on the sea water pump system where this is introduced):

** Some of these systems may continue to supply this flushing mixture into the system upon shut down, as per what I think "slauder" is referring to.
These may circumvent the RPM driven or regulated principle!
So for my way of thinking, this may cause more flow than what the exhaust system would normally require upon engine shut down. The risk being....... excessive water/mixture whereby we may undergo water reversion during those last few engine revolutions.
Of course this mixture would need to get past the impeller. Some say that it can..... some say that it cannot..... so this where theory comes into play on my behalf

** Some flushing systems connect in a way that simply allows for the Sea Water pump to "pull" it in, and I believe that this is a much safer means, since the normal sea water supply is RPM driven (regulated).
I think that the risk is reduced (upon shut down) with this type of flushing system.


Ideally, we'd completely shut off the sea water supply (flushing system) several seconds prior to actual shut down.
The exhaust and engine would not know the difference, but we'd eliminate any risk of reversion into an open exhaust port.
That would be my procedure if I were to use one of these flushing systems.


Just my two and a half cents worth. :D
 
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In my opinion....it won't make any noticable difference as to when you "should" replace the risors and elbows. Are you going to remove them just to inspect them and replace the gaskets and bolt kits every few years. I just got 12 years out of risors and elbows on a 454 Crusader that is only run 40 to 70 hours per year in salt water. Your mileage may vary.
 
two big ones come to mind:

1) corrosion 'parts' clog the raw water discharge into the exhaust stream - causes engine to overheat and can damage exhaust hose connected to elbow if enough reduction in water flow occurs.

2) corrosion may weaken the cast iron enough for the water injection point to 'move' and permit the raw water to enter the manifold's exhaust gas passage. if sufficient water accumulates, it will enter the cylinder with an open exhaust valve....hydrolock of engine is a likely outcome.
 
That 12 year life is something I have never experienced. I don't have risers, but my upper elbow slowly clogs after 4 years. I had a OEM crusader elbow actually suddenly plug shut at 5 years of life, during a fast cruise well offshore. No warning on the dash, my wife happened to be looking aft and said "is that smoke normal"? Very lucky we caught that before the exhaust rubber hose completely burned thru.
 
Ahhh, that's right, a hole in 4" exhaust is a very large hole in the boat since it under water line. I guess the rubber is melting hot until the boat is sinking.
 
diver_dave said:
NO, not when used in salt water. All salt water cooled jacketed iron exhaust hardware needs to go every 4 years.
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the picture is my crusaders. I thing i heard "log style" to describe my type of exhaust manifold. I have a S shape up after the manifold (is a riser?) and then the S shape down is the ehaust elbow? Just to confirm those two parts are on a 4 year cycle, correct? Aslo are these both called elbows and I dont have risers? I always thought we all had risers, but Dave you dont, so maybe this is same setup.
 

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You have the older LOG style. From the manifold's back end, you have a riser (upleg) and then the elbow (downleg where the exhaust hose connects). They look FWC'ed so there likely to be a blockoff plate between the manifold and the riser. A four year cycle should be hassle free; depending upon your use and the local wter composition, you may be able to get a couple more years out of a set.

The need for risers is driven the the particular hull and the engine's installation in it. There needs to be a certain vertical drop between the exhaust outlet and the manifold. (See the crusader installation manual for details.) Risers of different heights provide the means to achieve that minimum 'height'.
 
Not that I have yet to have more than 2 cycles of elbow changes BUT.... I am a volume reader and in the two forums I read religously, engine cooling issues seem to take the forefront of importance in people's boating lives. I am going to take a guess that 75% of these issues is poor flow of water thru one of the components and by failing to replace "X" part in a timely manner, the effect of the problem dominoes into more serious issues.

Having said that, when my elbows recently hit the 4 year mark, and reading DD's posts this year in response to others, and my temps rising a few degrees, I just changed the elbows ( aside form annual regular maintenance stuff over the seasons) and we are back to normal. It just seems easier that way rather than trying to stretch things out to a point of other component failures. Trust me, the economics of even simple replacements bites more these days but the value of reliability out weighs that.
 
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