Would flushing raw water side w/fresh H20 reduce corrossion?

[basssears]

Our boat does its fair share of sitting for long periods of time (2-3 months sometimes) as we are currently commuter boating. So I always think of the raw water just sitting in the raw water side of my (fresh water cooled w/heat exchanger) engine for months while we're gone.

Added to this, I am considering installing an oil cooler on our Hurth HBW10 transmission, and the cooler is basically just a raw water cooled heat sink that bolts onto the side of the transmission... best I can tell I would have to run this heat sink through the raw water side as the fresh water cooling circuit wouldn't be cool enough to do any real good drawing heat off the transmission. And the cooler is aluminum, so plenty of potential for corrosion and scaling etc. there.

My question is whether it would be worth the effort to run fresh water through the salt water circuit before we leave each time?

My thought would be to add a T with an inline valve to the raw water intake hose so I could close the raw water through hull valve, open the other "intake" valve that has a hose on it that goes into a 5 gallon jug of fresh water (with garden hose in it to keep it full in case I want to run for a few minutes), and run the engine while the fresh water flushes the existing salt water out of the system.

Potential upsides seem to me to be:

• No corrosive salt water sitting in the system, including new transmission cooler, while I'm gone
• Not hard to do the flush each time once I plumb in a second way to draw water into the raw water cooling circuit that I can use with fresh water (I don't want to pull the hose off the raw water through hull valve and stick it in a bucket each time).

Potential downsides seem to me to be:

• Maybe this doesn't help with corrosion anyway?
• Won't help with the scaling that happens when the raw water gets heated at the transmission cooler.
• Adding a t and a valve to the raw water intake circuit... I would use quality bronze Groco parts but still, more potential places for failure.
• Just introducing unnecessary complexity and another "to do" item when departing.

So does anyone flush the salt water out of their raw water circuit before leaving their boat?


As always, thanks in advance.


-- Bass

[barnaclejim]

I flush fresh water thru the raw water system when we are gone for prolonged periods by closing the thru hull fitting to the intake and running a hose thru the sea strainer with the engine running. I dont know if this prevents corrosion but especially in warm climes it prevents the salt and minerals from solidifying and plugging things up. Its easy to do and does not require another fitting. I also do this to the heads and it makes a big difference when we return , both in function and fragrance.

[Pitchondesign]

We leave our boat for 6 months and always fresh water flush. Definitely reduces the build up of scale and deposits. Salt water is more corrosive than fresh. Just look at boats used in fresh water compared to the ocean.

[basssears]

Originally Posted by barnaclejim

I flush fresh water thru the raw water system when we are gone for prolonged periods by closing the thru hull fitting to the intake and running a hose thru the sea strainer with the engine running. I dont know if this prevents corrosion but especially in warm climes it prevents the salt and minerals from solidifying and plugging things up. Its easy to do and does not require another fitting. I also do this to the heads and it makes a big difference when we return , both in function and fragrance.

Thanks... we already do this with the head and that's what got me thinking the engine might appreciate it.

Had been looking at the Groco SSCV inline valve to make this an easy process:
SSCV Safety Seacock
... but I hadn't thought of just flowing fresh water in the sea strainer... sounds pretty easy!

[SSgtPitt]

Would you guys mind "ess-plainin" this a little more...or directing me to a DIY site?
I'm on the boat every 6-8 weeks for 3-4 days and flushing my systems with fresh water never occured to me, but now seems like a why didn't I think of that moment.

[Sandibar]

I flush the raw water side every fall, before putting the boat on the hard for the winter. Easily done: close the seacock for the the raw water intake, then start the engine and pour water into the raw water filter/strainer. For winter maintenance I still pour in a 30% glycol solution after the fresh water rinse, so any retained water won't freeze and break the engine (not good for marine life, so the ejected glycol is best collected). Here's a video of how it's done, with some product placement Why Clean Raw Water Systems?

[Cheechako]

Originally Posted by basssears

Our boat does its fair share of sitting for long periods of time (2-3 months sometimes) as we are currently commuter boating. So I always think of the raw water just sitting in the raw water side of my (fresh water cooled w/heat exchanger) engine for months while we're gone.

Added to this, I am considering installing an oil cooler on our Hurth HBW10 transmission, and the cooler is basically just a raw water cooled heat sink that bolts onto the side of the transmission... best I can tell I would have to run this heat sink through the raw water side as the fresh water cooling circuit wouldn't be cool enough to do any real good drawing heat off the transmission. And the cooler is aluminum, so plenty of potential for corrosion and scaling etc. there.

My question is whether it would be worth the effort to run fresh water through the salt water circuit before we leave each time?

My thought would be to add a T with an inline valve to the raw water intake hose so I could close the raw water through hull valve, open the other "intake" valve that has a hose on it that goes into a 5 gallon jug of fresh water (with garden hose in it to keep it full in case I want to run for a few minutes), and run the engine while the fresh water flushes the existing salt water out of the system.

Potential upsides seem to me to be:

• No corrosive salt water sitting in the system, including new transmission cooler, while I'm gone
• Not hard to do the flush each time once I plumb in a second way to draw water into the raw water cooling circuit that I can use with fresh water (I don't want to pull the hose off the raw water through hull valve and stick it in a bucket each time).

Potential downsides seem to me to be:

• Maybe this doesn't help with corrosion anyway?
• Won't help with the scaling that happens when the raw water gets heated at the transmission cooler.
• Adding a t and a valve to the raw water intake circuit... I would use quality bronze Groco parts but still, more potential places for failure.
• Just introducing unnecessary complexity and another "to do" item when departing.

So does anyone flush the salt water out of their raw water circuit before leaving their boat?


As always, thanks in advance.


-- Bass

I had a little trawler for a while that was set up to do a fresh water flush. It's simple if you set it up, just a 3 way valve on the water intake with a hose fitting. Prior to that I did it by opening the top of the raw water strainer and putting the hose end in the strainer, allowing a bit of overflow if necessary.

[roverhi]

Flush with the engine running. Hooking up a hose to the salt water side of the cooling system without the engine running can/will back flow through the system filling whichever cylinder's valves are open with water. Even fresh water will rust the rust up rings, etc. if left in the cylinder for any length of time.

[Cheechako]

Originally Posted by roverhi

Flush with the engine running. Hooking up a hose to the salt water side of the cooling system without the engine running can/will back flow through the system filling whichever cylinder's valves are open with water. Even fresh water will rust the rust up rings, etc. if left in the cylinder for any length of time.

Mo Debbley!

[mikequig]

I installed a T-fitting with a shutoff valve in the line after the raw water seacock valve but before the strainer. To that valve I attached a 10-foot length of stainless braided washing machine hose. Now to the female end of the washer hose you can attach a garden hose to flush the engine with fresh water (closing the sea water seacock and opening the t-valve). The washing machine hose is just long enough to reach out of the engine compartment and up to the cockpit. A better method is to attach a SaltAway rig to the washing machine hose and flush with a mixture of SaltAway and fresh water.

[mikequig]

Here's a photo.

[michaelratinter]

I fill a 5 gallon bucket with fresh water and 1/4 cup of Saltaway and use it to flush the raw water system after every use. The PO built the boat with a tee and ballvalve to make the procedure painless.

[basssears]

Thanks everyone for the replies and mikequig thanks for the pictures, that's pretty close to what I was thinking of building out. Is that just a variety of Groco parts put together to make up the T and valve portion?

I also came across this "all in one" part Groco makes, I don't have any real interest in it as an emergency pump system because that idea seems to have been beaten to death, but I might just put one of these inline between the through hull and sea strainer and be done with it:
SSCV Safety Seacock

[basssears]

Originally Posted by Sandibar

I flush the raw water side every fall, before putting the boat on the hard for the winter. Easily done: close the seacock for the the raw water intake, then start the engine and pour water into the raw water filter/strainer. For winter maintenance I still pour in a 30% glycol solution after the fresh water rinse, so any retained water won't freeze and break the engine (not good for marine life, so the ejected glycol is best collected). Here's a video of how it's done, with some product placement Why Clean Raw Water Systems?

Thanks for the Sea Flush link, that looks like another good option. In my mind there are pros and cons to both permanently installed solutions like the one in the mikequig's post (the easier it is to do the more likely it will happen) and to non permanent installations (less up front effort and fewer permanent components to fail, valves to exercise etc)

I appreciate everyone's input should put me on the right track.

[Compass790]

We fresh water flush thru a v/v & tee whilst running engine when we return to marina just allowing raw water pump to suck out of bucket which is being replenished by dock hose. It seems to reduce buildup of deposits & extend anode life. We use plastic/composite v/v's & fittings everywhere except where heat is a factor & have no trouble with them. They seem to cope with not being operated much better than metal ones.