Logo
FULL SITE MENU

Help a long time outboard guy out......

Ply

Ply

Contributing Member
Hello all...

I am attaching a photo of one of my new to me 454 FWC engines.

As a humble man I was hoping someone could basically dumb down the cooling system "pathway."

I have an obvious general understanding of Marine cooling systems, but i'm not 100% sure of exactly what would be subjected to raw water in this system. Obviously the risers would be, but how about the manifolds in this engine?

Any explanation of the hoses running to and from the heat exchanger would be appreciated.....

I guess i'm wondering where the RAW water goes?? and doesn't go...

Picture will be on following reply as I'm having issues attaching it with text here... apparently i'm technologically challenged as well as cooling system challenged...lol....
 
Simply put, The raw water pump will cool the coolent that runs through your engine's heat exchanger and when it is done then it will go out your exhaust. The manifolds will be fresh water cooled and the elboes are raw water cooled. So you will end up having to replace the elboes at some point but not the manifolds themselves. If I have not described this quite right then some one will speak up which is the great thing about this site. Have a safe and merry Christmas.
 
By elbows you mean the risers? Or do you also refer to the actual cast elbows downstream of the engine?? or likely BOTH?
 
If you're OK with this, I'll be very elementary as though you know very little..... No offense!

Let's use the term Closed Cooling system in lieu of FWC.
Let's refer to the river/lake/ocean water as seawater.
With regard to exhaust, we'll have Manifolds, Spacers/Risers (optional) and Elbows. (you do not have spacers/risers)
With regard to the coolant.... let's use "E/G" (ethylene glycol) although "coolant" will work.



By elbows you mean the risers? Or do you also refer to the actual cast elbows downstream of the engine?? or likely BOTH?
Click to expand...
A very common misnomer.
Manifolds we all understand, but Spacers/Risers are often confused with Elbows and sometimes visa-versa.
Even some manuals and ads list them incorrectly.

Here's a spacer/riser.

Here's an elbow.


Ply said:
I have an obvious general understanding of Marine cooling systems, but i'm not 100% sure of exactly what would be subjected to raw water in this system. Obviously the risers would be, but how about the manifolds in this engine?

Any explanation of the hoses running to and from the heat exchanger would be appreciated.....

I guess i'm wondering where the RAW water goes?? and doesn't go...

Picture will be on following reply as I'm having issues attaching it with text here... apparently i'm technologically challenged as well as cooling system challenged...lol....
Click to expand...

OK.... I've marked up your picture to show which is which, etc.

Seawater is pumped into the shell and tube style Heat Exchanger, and passes through the tube bundle.
Your engine has ethylene glycol (coolant) being pumped through it, and additionally through your manifolds.
The hot E/G coolant returns to the H/E and sorrounds the tube bundle.

As the seawater passes through the tube bundle, it removes engine and manifold heat from around the tube bundle (the E/G side of the system), much like air does with a Car/Truck radiator.
So basically, the car/truck radiator has been replaced with a Heat Exchanger, and the air has been replaced with seawater.

The "spent" seawater is then directed to the exhaust elbows, where it then eventually blends with the exhaust gasses.
 

Attachments

  • Ply Crusader CCS.jpg
    Ply Crusader CCS.jpg
    66.1 KB · Views: 271
Last edited:
Ricardo you're amazing and NO offense taken. I do know the basics but that graphic sure was helpful!! It's posts like your graphic that will forever be archived on this site to continue to help others down the road who might be afraid to ask. Your input here is like no other i've seen. Thank you.

So back to my ignorance. I other question.

How about the actual exhaust elbow that is to the left of "I" between the rubber exhaust hoses.... That cast iron elbow... it sees sea water and exhaust gasses so how often do they typically need to be examined???
 
Ply said:
Ricardo you're amazing and NO offense taken. I do know the basics but that graphic sure was helpful!! It's posts like your graphic that will forever be archived on this site to continue to help others down the road who might be afraid to ask. Your input here is like no other i've seen. Thank you.
You are too kind, thank you!

So back to my ignorance. I other question.

How about the actual exhaust elbow that is to the left of "I" between the rubber exhaust hoses.... That cast iron elbow... it sees sea water and exhaust gasses so how often do they typically need to be examined???
Click to expand...
Good question.

If you are speaking about the part to the left of the "I", that joining elbow looks to be fiberglass, and can be removed and inspected.

If you are speaking of the actual cast iron exhaust Elbow (where you see the rubber exhaust coupler connecting to it) ...... just inside of this area is the seawater mixing chamber.
There will be a small port or series of ports where the spent seawater blends with the exhaust gasses (shown by the arrows).
These will eventually rust up and become restrictive, and when they do, we typically begin to see over-heating issues.

Sometimes these ports can be cleaned and cleared, yet often in salt water it's a lost cause and requires replacement.
I'd suggest that you periodically pull the elbows and inspect them.
However, in your scenario you'll likely not need to replace your manifolds.

On open systems (raw water cooled) the seawater transfer ports also become rust restricted, and again we typically begin to see over-heating issues.



.
 
Last edited:
Yes I was referring to the elbow to the left of the "I" which appears to you to be fiberglass... Basically it's the BLACK Colored elbow i'm asking about

I never realized they used Fiberglass in the exhaust system... So towards the stern there is another exhaust elbow is that likely fiberglass as well??

(This boat is new to me and still out of state otherwise I could go outside and touch it and know...lol...)
 
Somewhere in your raw (sea water) water circuit you should also have an oil cooler. This will be either immediately before or immediately after the raw water pump. This small heat exchanger either cools the engine oil, or has double circuits so it can cool the engine oil and the transmission oil. It is one of those many things on a boat that few worry about (until it fails...).

You did not say how old the motors are. For the most part service on the raw water side is a function of time (not engine hours). The raw water pump has a rubber impeller and many boaters change them every year, or two years at most. Long periods of idle (like winter) are hard on them and some boaters remove during layup. There are threads on the subject on this forum. You should also check the pumps regularly to insure they are not dripping (bad shaft seal). If they drip the salt will get on the pulleys leading to rust and belt wear. Pumps can be rebuilt to replace seals but I find it simpler and not much more expensive to just buy new one.

The cast iron elbows are also a regular service item. As has been noted if they clog cooling flow is reduced and that will be evident. But the real issue is if holes rust though in the cooling passages, then when the engine is not running salt water can drip down into the exhaust manifold and into the engine though an open exhaust valve. There are many threads on this, but the results of the leak can range from annoying to total engine destruction. So you want to change them out before they leak. The particular sea water you are in seems to be the biggest life factor so talking to others at your marina may be a good idea. Four years between changes seems pretty typical (assuming you buy a reputable brand elbow) but one hears reports of failure in three years, or perhaps going ten years without a problem. My first leak was at four years so I am down to three between changes.

Other than service the zincs in the heat exchanger (and oil cooler if it has zincs) most boaters wait until there is a cooling problem or evidence of a leak to do anything else on the raw water side.
 
All great points, CaboJohn.... The motors are 95's with low hours (Which really is a mute point like you said when it comes to raw water issues).....

Thank you again guys!!!
 
CaboJohn said:

1...... Somewhere in your raw (sea water) water circuit you should also have an oil cooler. This will be either immediately before or immediately after the raw water pump. This small heat exchanger either cools the engine oil, or has double circuits so it can cool the engine oil and the transmission oil. It is one of those many things on a boat that few worry about (until it fails...).

2..... You did not say how old the motors are. (a) For the most part service on the raw water side is a function of time (not engine hours). The raw water pump has a rubber impeller and many boaters change them every year, or two years at most. (b) Long periods of idle (like winter) are hard on them and some boaters remove during layup. There are threads on the subject on this forum. You should also check the pumps regularly to insure they are not dripping (bad shaft seal). If they drip the salt will get on the pulleys leading to rust and belt wear. Pumps can be rebuilt to replace seals but I find it simpler and not much more expensive to just buy new one.

The cast iron elbows are also a regular service item. As has been noted if they clog cooling flow is reduced and that will be evident. But the real issue is if holes rust though in the cooling passages, then when the engine is not running salt water can drip down into the exhaust manifold and into the engine though an open exhaust valve. There are many threads on this, but the results of the leak can range from annoying to total engine destruction. So you want to change them out before they leak. The particular sea water you are in seems to be the biggest life factor so talking to others at your marina may be a good idea. Four years between changes seems pretty typical (assuming you buy a reputable brand elbow) but one hears reports of failure in three years, or perhaps going ten years without a problem. My first leak was at four years so I am down to three between changes.

3.... Other than service the zincs in the heat exchanger (and oil cooler if it has zincs) most boaters wait until there is a cooling problem or evidence of a leak to do anything else on the raw water side.
Click to expand...

John makes some good points!

1..... Your oil cooler is to the right of my "F" (in the marked up photo), and I believe this is what the guys refer to as a U-cooler!
Seawater enters the cooler at the lower area in the picture, and exits from the upper area in the picture, and heads toward the Heat Exchanger's port "I".

2..... Several great points here.

3.... As for anodes, yes..... listen to John. Keep these renewed.... sometimes multiples times annually.
And be Pro-Active..... don't wait until signs of failure begin to show up!


Ply said:
All great points, CaboJohn.... The motors are 95's with low hours (Which really is a mute point like you said when it comes to raw water issues).....
Click to expand...
I agree..... low run time hours are rather moot when it comes to Old Father Time.



And more importantly..... Merry Christmas to you guys.

I got up early so that I could speak with Santa..... but so far I haven't seen him!

.
 
Last edited:
Ricardo:3.... As for anodes, yes..... listen to John. Keep these renewed.... sometimes multiples times annually.
And be Pro-Active..... don't wait until signs of failure begin to show up!

God I feel stupid asking this but the heat exchanger zincs...(Pencil zincs??) where inside of the exchanger are they located? I guess i'm wondering how you access them?? from the sides? How about the anodes in the u-cooler?

and yes, MOST importantly, Merry Christmas to all!!!

Santa managed to avoid me as well.... maybe I stumbled in a little late for him
 
Last edited:
Ply, technically these are "anodes", or more properly "sacrificial anodes".
Anode material can range from Zinc to Aluminum or to Magnesium...... depending on what's being protected and what water (i.e., fresh or ocean)

Yes.... the term "pencil anode" is correct.

As Kim showed us...... some pencil anodes for heat exchangers do offer replacement anodes that thread into the brass fitting. When they have given up all of the anode material, we simply R&R the pencil portion, and re-install.

However, you'll see that some of pencil threads are Metric and some are US.

When you buy your pencil anodes, it's best to buy a butt load of replacement pencils at the same time.

.
 
Last edited:
Ricardo, I like the idea of buying a butt load (Yes that is an international unit of measure by the way :) ) WHEN I find the right ones...

What is the rule of thumb when looking for the pencil zincs?? obviously I will match the thread and actual bronze NPT threads for the head of the zinc...

BUT how deep?? What is safe? Is it basically just NOT touching the coils inside??
 
Ply said:
Ricardo, I like the idea of buying a butt load (Yes that is an international unit of measure by the way :) ) WHEN I find the right ones...

What is the rule of thumb when looking for the pencil zincs?? obviously I will match the thread and actual bronze NPT threads for the head of the zinc...

BUT how deep?? What is safe? Is it basically just NOT touching the coils inside??
Click to expand...

When you buy your new Pencil ANODES :D :D, they will be of the standard length and diameter.

The base threads should be 1/4" tapered pipe.
The anode itself threads into the sea water side of the shell. It won't penetrate the ethylene glycol side.


.


.
 
Back
Top