fresh water vs raw water cooling

[hottoddie]

Great info, I am not in salt water, but guessing a fully closed cooling system would eliminate winterizing the motors.... which I would love to be able to boat earlier and later in the season without fear of freezing

You still need to winterize the sea water cooling side of the cooling system. It is just easier.

 

[Gallf1]

Any one has experience with FLUSHPRO from Perko ? my boat in saltwater all year round. - replaced last year manifolds, risers and elbows.. - would be good to flush the whole system time to time with " fresh " water ?

https://www.perko.com/catalog/underwater_hardware/62/flush_pro/

I looked at those when I was building a freshwater flushing system for my 454'

Any one has experience with FLUSHPRO from Perko ? my boat in saltwater all year round. - replaced last year manifolds, risers and elbows.. - would be good to flush the whole system time to time with " fresh " water ?

https://www.perko.com/catalog/underwater_hardware/62/flush_pro/

I looked at those when building a flushing system for my twin 454's and Gen Set. I didnt like the plastic body and electric set up so I went with Bronze 3-way full flow valves and quick connect hose couplers between the seacock's and strainers.

What i have is a 5 gallon bucket with a hose attached (via bronze fitting installed in the bottom of the bucket). After every outing, I shut off the seacocks (no salt water in), connect the bucket/hose (via hose quick coupler), fill the bucket with a running garden hose and open the 3-way valve to pull water out of the bucket. I then crank the engine and let it run for 4-5 minutes before I turn off the garden hose and quickly throw in about 4-5oz of Salt Away (recommended dilution). By the time the engine has pulled all of the freshwater/Salt Away mix out of the bucket, you will see some suds coming out of the exhaust discharge (you now know the mixture has made it all the way thru the engine) then I shut down motor and close the 3 way valve and remove hose. Salt Away mixture stays inside cooling system (beginning at the strainer all the way thru the water lift muffler).

This provides the benefit of a freshwater rinse and correct dilution of a Salt Away treatment to everything that is touched by raw water.

I know it is reducing rust inside the motors as when I crank the motors for the next trip, no rust comes out of exhaust and there is no rust staining on the hull. I have pulled risers several times when working on other parts of engine and there is minimal surface rust.

 

[Mark007]

Hey folks hoping you can help advise me similar thinking on this thread. I just bought a used 2005 Sea Ray 320 with Twin 350 Mercruiser (5.7L) MAG MPI Horizons V drive engines. The port side engine just failed with milky oil and salt water in engine. I ordered 2 new engine cores and we will reuse sea water pumps, alterators and other components. I really wanted to convert the new rebuilt engines over to full fresh water cooled heated exchangers. I have been looking at after market options but am concerned at the idea that the ECM needs to be replaced also. Does anyone have advice on if ECM can be reprogrammed or needs to be replaced? Can anyone comment on aftermarket dealer vs OEM? OEM per engine is $6300 CAD$$. That is about $4000 US per side!! Yes I know I can flush with hose kit everytime but there are times when I will not have a hose around for weeks at a time. Thanks.

 

[sbw1]

Hello all, should be an easy answer for a lot of people on this forum

I have a 2000 380 DA with the 7.4 Horizons. Fresh water cooled, always on a lake in middle USA

What does the freshwater cool, and what does the raw water cool?

Curious what, if anything, i need to plan for items like oil coolers for a boat that is in lake water...

Thanks in advance

Chris

There are raw watered cooled boats from west Michigan that have never had any cooling plumbing replaced and are not worn out. My 1986 WeekEnder still has its original engines which are nearing the end of their lives from high hours. It's manifolds and risers are still fine. The boat looks awful as the current owner fished it and did little cosmetically to keep it up. Probably skimped on the maintenance too but it still raises fish. Then there are the old wooden Chris Crafts with original Grey marine engines. So things last a longtime in fresh water if you do basic maintenance. I've boated for 50 years on the Great Lakes and have never heard of people replacing or even checking raw water systems that have been properly winterized. I have seen or heard about a number of improper winterizing projects that did not end well.

 

[Mavado007]

I looked at those when I was building a freshwater flushing system for my 454'

I looked at those when building a flushing system for my twin 454's and Gen Set. I didnt like the plastic body and electric set up so I went with Bronze 3-way full flow valves and quick connect hose couplers between the seacock's and strainers.

What i have is a 5 gallon bucket with a hose attached (via bronze fitting installed in the bottom of the bucket). After every outing, I shut off the seacocks (no salt water in), connect the bucket/hose (via hose quick coupler), fill the bucket with a running garden hose and open the 3-way valve to pull water out of the bucket. I then crank the engine and let it run for 4-5 minutes before I turn off the garden hose and quickly throw in about 4-5oz of Salt Away (recommended dilution). By the time the engine has pulled all of the freshwater/Salt Away mix out of the bucket, you will see some suds coming out of the exhaust discharge (you now know the mixture has made it all the way thru the engine) then I shut down motor and close the 3 way valve and remove hose. Salt Away mixture stays inside cooling system (beginning at the strainer all the way thru the water lift muffler).

This provides the benefit of a freshwater rinse and correct dilution of a Salt Away treatment to everything that is touched by raw water.

I know it is reducing rust inside the motors as when I crank the motors for the next trip, no rust comes out of exhaust and there is no rust staining on the hull. I have pulled risers several times when working on other parts of engine and there is minimal surface rust.

Not havind easy enough access to do this

 

[Fernando Ruarte]

Hello All!
I am super happy. I just bought a 1999 Sundancer 310 with 350 MAG MPI (Bluewater Inboard) With V -drives . I love the wider beam of the older models.

It is raw water cooled. I understand the differences between the RWC and FWC.

The boat lived in lakes in AZ all of its life and dry stored during winter. Engines have 400 HOURS.

I tested it for 3 days in a Lake before buying it. The engine runs like a charm. Compression is 165 on all cyls.

It will be kept in the San Francisco Bay in Salt water.

My old boat was a 2005 Glastron 279 with a volvo penta 5.7 RWC and inboard/outboard. I replaced the manifolds and risers right away by myself for $900 bucks (the old ones were close the 90% clogged after the boat sat on a dock for 3 years). The engine had 150 hours when I bought it. I never had a problem with the engine in the 18 months I owned it. Temp stays locked at 155 even after a 6 hour ride non stop to Sacramento.... The local Volvo shop told me that the engine was solid and as long as I used it regularly a couple of times a week, I didn't even need a flush system. He said that my radio would rust faster than the engine... But I spent the cost of the boat on issues with the stern drive...

Since then I learned my lesson... SALT WATER = INBOARD ONLY FOR ME

I do acknowledge that a lot of fisherman use RWC engines in salt water with no problems as long as they maintain them well.

Now, back to my question:
I considered installing a FWC system kit on my Sea Ray 310 with 350 MAG MPI (Bluewater Inboard). Part number 710-860427a 5. Each kit is about $2000 and the mechanics would charge $1500 on each engine.

One of the top shops in the bay questioned my choice... he said that a 20 year old engine is not worth the money of the FWC system investment. He said that I could just install a good flushing system and leave it alone. At some point, I should change manifolds and risers and that would be it. He said that on a boat that old, the resale value of FWC vs RWC is not worth the investment in the FWC conversion...

I read a number of forums about FWC vs RWC. There are pros and cons of each and many well fundamented beliefs of do's and don't do's.

I literally considered launching the boat in the river, installing the the FWC kit and ONLY THEN going to the bay.... but the logistics of my transport are leading to getting the boat on the Bay's salty water next week...

My Kid is really into this boating thing so we'll definitely go out a few times a month and probably run the engine for 2-3 hours each time.

I would appreciate some guidance on what you would do if it was your boat.
1. Would you just install a flush kit , make sure i flush it after each use and leave it alone?
2. Would you run it on the bay in salty water till the end of the season and spend the $7K upgrading to FWC after doing a good flush of the cooling system?
3. Should I just run it and inspect manifold and risers at the end of the season?
4. Other ideas?

I found it cool that a reputable Merc mechanic shop told me to leave it alone instead of selling me a huge project...

Any comments, ideas and food for thought are appreciated.

Thanks
Fer

 

[Gallf1]

Hello All!
I am super happy. I just bought a 1999 Sundancer 310 with 350 MAG MPI (Bluewater Inboard) With V -drives . I love the wider beam of the older models.

It is raw water cooled. I understand the differences between the RWC and FWC.

The boat lived in lakes in AZ all of its life and dry stored during winter. Engines have 400 HOURS.

I tested it for 3 days in a Lake before buying it. The engine runs like a charm. Compression is 165 on all cyls.

It will be kept in the San Francisco Bay in Salt water.

My old boat was a 2005 Glastron 279 with a volvo penta 5.7 RWC and inboard/outboard. I replaced the manifolds and risers right away by myself for $900 bucks (the old ones were close the 90% clogged after the boat sat on a dock for 3 years). The engine had 150 hours when I bought it. I never had a problem with the engine in the 18 months I owned it. Temp stays locked at 155 even after a 6 hour ride non stop to Sacramento.... The local Volvo shop told me that the engine was solid and as long as I used it regularly a couple of times a week, I didn't even need a flush system. He said that my radio would rust faster than the engine... But I spent the cost of the boat on issues with the stern drive...

Since then I learned my lesson... SALT WATER = INBOARD ONLY FOR ME

I do acknowledge that a lot of fisherman use RWC engines in salt water with no problems as long as they maintain them well.

Now, back to my question:
I considered installing a FWC system kit on my Sea Ray 310 with 350 MAG MPI (Bluewater Inboard). Part number 710-860427a 5. Each kit is about $2000 and the mechanics would charge $1500 on each engine.

One of the top shops in the bay questioned my choice... he said that a 20 year old engine is not worth the money of the FWC system investment. He said that I could just install a good flushing system and leave it alone. At some point, I should change manifolds and risers and that would be it. He said that on a boat that old, the resale value of FWC vs RWC is not worth the investment in the FWC conversion...

I read a number of forums about FWC vs RWC. There are pros and cons of each and many well fundamented beliefs of do's and don't do's.

I literally considered launching the boat in the river, installing the the FWC kit and ONLY THEN going to the bay.... but the logistics of my transport are leading to getting the boat on the Bay's salty water next week...

My Kid is really into this boating thing so we'll definitely go out a few times a month and probably run the engine for 2-3 hours each time.

I would appreciate some guidance on what you would do if it was your boat.
1. Would you just install a flush kit , make sure i flush it after each use and leave it alone?
2. Would you run it on the bay in salty water till the end of the season and spend the $7K upgrading to FWC after doing a good flush of the cooling system?
3. Should I just run it and inspect manifold and risers at the end of the season?
4. Other ideas?

I found it cool that a reputable Merc mechanic shop told me to leave it alone instead of selling me a huge project...

Any comments, ideas and food for thought are appreciated.

Thanks
Fer

My opinion...
A RWC boat that lives in saltwater should be flushed after every use (when feasible) so as to prolong the life of the exhaust manifolds, risers and elbows. With a flushing system and a salt removing product (I use "Salt Away), you can can greatly extend the time frame of replacing these items.

If money is not an issue, then dont flush and just plan on automatically replacing those items every 2-3 years like clockwork.

On my system (that I installed), you close the raw water intake seacocks and open an inline valve that is between the seacock and the strainer. The valve is connected to a short piece of reinforced hose that you drop in a 5-gallon bucket kept full of fresh water by a running garden hose from the dock. Crank the motor and let the engine pull the fresh water from the bucket for 5 mins or so....when you are ready to shut down, turn off the garden hose in the bucket and quickly dump 4oz of Salt Away to the bucket. Shut down the engine when the bucket is empty (but dont let your impeller run dry!!).
With the Salt Away product you should see some suds/foam come out of your exhaust water outside the hull. Then turn off your flushing valve and leave the fresh water/Salt Away mixture inside the engine.
You have now rinsed out any salt water from your cooling system and greatly reduced internal corrosion.

Anything cooled by seawater needs to be inspected at around 100 hours regardless of flushing in my opinion. I installed new OEM elbows and manifolds 3 years ago and have been flushing after every use. I know my flushing process is working as I dont have any rust stains on the hull by the exhaust ports and when I crank it before going out, the water comes out clear with the Salt Away mixture (no rust in water). My first inspection will be this winter before our trip to the Dry Tortugas off of Key West.

 

[Christo]

Dumb question here, but how do you know if your engine is RWC or FWC cooled? Mine is a 2004 Mercruiser 5.0 MPI Bravo 3, I’m in freshwater. Is it in the manual?

 

[Chip S]

Dumb question here, but how do you know if your engine is RWC or FWC cooled? Mine is a 2004 Mercruiser 5.0 MPI Bravo 3, I’m in freshwater. Is it in the manual?

If the engine is FWC you'll see a metal tube (heat exchanger) on the engine. If it doesn't have a heat exchanger it is RWC.

 

[Christo]

Gotcha, thanks Chip

 

[northern]

Our engines in salt water with antifreeze system have 3,500 hours on them the risers rust out every 5 years. I assume the engines would rust at the same rate. 2,000 seems like a good price but low. The heat exchangers are cost about 1,000 each.

 

[Fernando Ruarte]

Our engines in salt water with antifreeze system have 3,500 hours on them the risers rust out every 5 years. I assume the engines would rust at the same rate. 2,000 seems like a good price but low. The heat exchangers are cost about 1,000 each.

wow!

How often do you go out?

 

[Fernando Ruarte]

My opinion...
A RWC boat that lives in saltwater should be flushed after every use (when feasible) so as to prolong the life of the exhaust manifolds, risers and elbows. With a flushing system and a salt removing product (I use "Salt Away), you can can greatly extend the time frame of replacing these items.

If money is not an issue, then dont flush and just plan on automatically replacing those items every 2-3 years like clockwork.

On my system (that I installed), you close the raw water intake seacocks and open an inline valve that is between the seacock and the strainer. The valve is connected to a short piece of reinforced hose that you drop in a 5-gallon bucket kept full of fresh water by a running garden hose from the dock. Crank the motor and let the engine pull the fresh water from the bucket for 5 mins or so....when you are ready to shut down, turn off the garden hose in the bucket and quickly dump 4oz of Salt Away to the bucket. Shut down the engine when the bucket is empty (but dont let your impeller run dry!!).
With the Salt Away product you should see some suds/foam come out of your exhaust water outside the hull. Then turn off your flushing valve and leave the fresh water/Salt Away mixture inside the engine.
You have now rinsed out any salt water from your cooling system and greatly reduced internal corrosion.

Anything cooled by seawater needs to be inspected at around 100 hours regardless of flushing in my opinion. I installed new OEM elbows and manifolds 3 years ago and have been flushing after every use. I know my flushing process is working as I dont have any rust stains on the hull by the exhaust ports and when I crank it before going out, the water comes out clear with the Salt Away mixture (no rust in water). My first inspection will be this winter before our trip to the Dry Tortugas off of Key West.

Thanks for the deep insight!

more questions;

1. I have seen some strainers with a cap that is built so you can easily hook a hose into to connect the salt away type system. Has anyone seen those?

2. some systems allow you to plug a hose directly and then get the water pressure from the city water. I have read about concerns that too much pressure could push beyond the sealing capability of some of the gaskets and seals in the system surrounding the raw water pump. Does any one know what is the maximum PSI that system should be exposed to? how much volume of water does the raw water pump really suck?

3. If i install a T with a valve between the seacock and the strainer to inject the salt away, what is the best way to make sure it never gets air into it? I read that a little air while running or when stopped can cause many issues

 

[northern]

wow!

How often do you go out?

2 to 3 months in the spring/summer and all of September.

 

[northern]

Thanks for the deep insight!

more questions;

1. I have seen some strainers with a cap that is built so you can easily hook a hose into to connect the salt away type system. Has anyone seen those?

2. some systems allow you to plug a hose directly and then get the water pressure from the city water. I have read about concerns that too much pressure could push beyond the sealing capability of some of the gaskets and seals in the system surrounding the raw water pump. Does any one know what is the maximum PSI that system should be exposed to? how much volume of water does the raw water pump really suck?

3. If i install a T with a valve between the seacock and the strainer to inject the salt away, what is the best way to make sure it never gets air into it? I read that a little air while running or when stopped can cause many issues

On our jetboat I did "T" and it provides enough cooling to run the boat on land. I did it because one winter we took boat to Mexico and left it in ocean for 4 months. I have no idea if flushing it did any good. New engine is 20K installed if they will do each engine for 2K it seems to me like a good idea. We never flush the salt water system on the SeaRay and the risers last 5 years.

 

[Brite Idea]

So I'm going to give you my opinion and you can go from there but backed up by my experience. My last boat was a lake boat that I added closed cooling to but only a half system because V6's can't pump enough water for a full system. This meant I had to do risers and manifolds every five years, period. The boat served me well for 17 years in saltwater and the boat sold last year for 10K more than the NADA suggested price. I asked the buyer how come he bought it and he said that he had looked at much newer boats that didn't come close to how good mine looked. I asked how so? He said the engines looked almost new. Look at most raw water cooled engines in saltwater and they're rusty everywhere.
I then went out and bought a bigger lake boat raw water cooled and over the winter had closed cooling installed. My mechanic and I had the conversation about flushing vs. closed cooling and his experience is most people get tired real quick of the hassle of flushing. Also since I'm cooling the manifolds they should the life of the engines.
So if I bought the boat that you bought I'd install a full closed cooling system and you'll have extended the life of your current engines possibly for as long as you will own the boat.

 

[Pirate Lady]

Hey Fernie,i read this twice see if i got this right. Tell me if i wrong.
$7k to convert to FWC.
$900 to replace mans & risers.
So you can replace the parts 7 times and still be less then the conversion.
Replace every 4 years, ya they dont get eaten faster than that, you’re looking at 28 years and still haven’t recovered your FWC investment.
Planning on saving the boat for the grand kids?

 

[northern]

Hey Fernie,i read this twice see if i got this right. Tell me if i wrong.
$7k to convert to FWC.
$900 to replace mans & risers.
So you can replace the parts 7 times and still be less then the conversion.
Replace every 4 years, ya they dont get eaten faster than that, you’re looking at 28 years and still haven’t recovered your FWC investment.
Planning on saving the boat for the grand kids?

The block will corrode at the same rate as the risers in salt water probably in raw water system

 

[Pirate Lady]

The block will corrode at the same rate as the risers in salt water probably in raw water system

Uh, no. Replaced mans risers over the 30 years on this engine, original block, by your logic i need to replace the block every 5 years like the exhaust parts.

 

[northern]

Uh, no. Replaced mans risers over the 30 years on this engine, original block, by your logic i need to replace the block every 5 years like the exhaust parts.

Thicker = longer life for block I would expect. Cast iron sewer pipe is good for 50 years but it is not under pressure and not in salt water