Volvo Penta 740B raw water cooling

[GCMarine]

Hi. I have a 1993 VP 740B. We installed an aftermarket closed cooling system and started running the boat in salt water 5 or 6 years ago. I just learned that the boat has stock coolers for the oil and power steering fluid that are mounted on the raw water intake circuit so they are not protected by the closed cooling system. I'm guessing that, after 5+ years in salt water, those two coolers are probably on borrowed time, so I'm planning to replace them. Can anyone tell me if these are constructed with any kind of salt protection - or if they have fittings for anodes or some other protection? Is it advisable to re-route the closed cooling to incorporate these two coolers? Or do others just run them for a few years and replace them? Thanks for your help.

 

[Scott Danforth]

If you flush, the coolers are fine

 

[GCMarine]

Thanks for your reply, Scott. I forgot to mention that the boat is moored in salt water for ~4months each year. Does that change your answer at all?

 

[Lou C]

Here’s my answer:
I have the original power steering cooler on my 1988 OMC Cobra that has been run & moored in salt water for about 20 years (6 month season) it hasn’t leaked yet. But I do have a spare just in case. It only gets flushed at the end of the season.

 

[Scott Danforth]

Thanks for your reply, Scott. I forgot to mention that the boat is moored in salt water for ~4months each year. Does that change your answer at all?

no, the copper coolers are the same design as your heat exchanger you added to the engine.

at most, you need to defoul them as little critters (barnacles ) tend to grow on the raw water side

you should be running barnacle buster once a year as maintenance

 

[bruceb58]

I had an oil cooler fail on my 7.4L Volvo Penta but was likely just metal fatigue rather than corrosion that caused it to fail.

 

[Lou C]

no, the copper coolers are the same design as your heat exchanger you added to the engine.

at most, you need to defoul them as little critters (barnacles ) tend to grow on the raw water side

you should be running barnacle buster once a year as maintenance

OK got a question for you Scott, what would be a good (safe) procedure for using the Barnacle Buster?
I have this as an idea let me know what you think...
I have one of those winterizing tanks I never used for winterizing (only would have if I had closed cooling) I turned it into a flush tank for my drum brakes, it has a live well pump to pressurize the flow. So, how about using this to pull in the BB, then after its more or less full (approx 5 gallons I figure based on the amount of antifreeze I use to winterize it by back filling it) leave that in, for the amount of time recommended by BB, then flush with fresh water....thoughts?

 

[Scott Danforth]

on the VP's and bravo's, we recommended a plastic immersion pump, a large tub, pull the impeller and use a set of muffs as the pratice

the immersion pump pumps the BB thru the system, and comes back out the exhaust and idle reliefs back into the tub. let it run for a half hour, then dispose of per your local regulations.

on your cobra, you can pull the impeller easy enough to do the same thing

 

[Lou C]

Sounds good, I have wanted to do this for a long time, based on my usage you get barnacles for sure in the lower unit, in fact I wound up having to remove that plastic screen OMC put in there (actually was the same as what was used on the OMC V6 outboards) because it was getting constantly fouled with barnacles despite painting with Trilux-II.

 

[GCMarine]

This is all super-helpful. Can't thank you all enough!

 

[Scott Danforth]

Sounds good, I have wanted to do this for a long time, based on my usage you get barnacles for sure in the lower unit, in fact I wound up having to remove that plastic screen OMC put in there (actually was the same as what was used on the OMC V6 outboards) because it was getting constantly fouled with barnacles despite painting with Trilux-II.

bud of mine's company makes a cavitation gun for the navy. it uses seawater and a high-pressure pump. what comes out of the nozzle is a stream of bubbles. as they burst, they explode the barnacles. the video is cool as heck.