Heat exchanger cleaning...

[MikeP]

Thought it might be interesting as I do my last maintenance on the boat to provide some info.

The pics below show the HEs as I pulled them today. They were last cleaned near the end of last season. The deposits are what occurred essentially over the winter EVEN though I flushed the HE's after each run prior to winterizing with fresh water through the zinc fittings.

First two pics are as they were when pulled. The third pic is what both looked like after approximately 60 seconds in the DD muriatic/oxalic acid/water mix. Since only 3 pics per post are allowed, and both cleaned HE's look the same, I figured one pic was sufficient.

Now actually, they "dirty" pics don't look all that bad BUT the thing to remember is that the little bit of deposits you can easily see, is duplicated throughout the entire HE, which internally is almost impossible to see or photograph. So that little bit of deposits probably reduces the HE capability by 20-30%. I admit I'm guessing about that but we all know that these DD cooling systems must be in almost perfect condition to allow WOT running for an unlimited period of time.

[Toolsntoys]

Thanks mike. When I did mine last spring I referred to your original post many moons ago. With the dd formula they came out like brand new in just a few min. Ok. It took a couple hours to pull them from the boat.

[bobk]

Mike, Please remind me, are they '92s or 71's? My 6V92's have been cleaned only twice (I think) in 11 years and I can run at 2000-2100 with out exceeding about 185F on the mechanical gages. I wonder if because the boat is moored in brackish water it makes a difference?

Bobk

[JonHupp]

Mike,

I honestly think you are one of the smartest 53 MY guys out there but I think you may have too much free time. If you are ever interested in crossing the bay and working on the Severn River, boy do I have a boat that needs some maintenance. All kidding aside, your posts are very, very informative.

Jon

[Mike in S Fla]

Thought it might be interesting as I do my last maintenance on the boat to provide some info.

The pics below show the HEs as I pulled them today. They were last cleaned near the end of last season. The deposits are what occurred essentially over the winter EVEN though I flushed the HE's after each run prior to winterizing with fresh water through the zinc fittings.

First two pics are as they were when pulled. The third pic is what both looked like after approximately 60 seconds in the DD muriatic/oxalic acid/water mix. Since only 3 pics per post are allowed, and both cleaned HE's look the same, I figured one pic was sufficient.

Now actually, they "dirty" pics don't look all that bad BUT the thing to remember is that the little bit of deposits you can easily see, is duplicated throughout the entire HE, which internally is almost impossible to see or photograph. So that little bit of deposits probably reduces the HE capability by 20-30%. I admit I'm guessing about that but we all know that these DD cooling systems must be in almost perfect condition to allow WOT running for an unlimited period of time.

Hey Mike getting ready to do mine is the acid a specific detroit formula or common muratic acid

thanks

[MikeP]

Thanks for the compliment, Jon. Being retired, all of my time could be called "free time," but working on boats/owning them) has dropped off my personal "free time" schedule.

Bob - The engines are 8V71TIs. I assume different water can make a difference in how fast stuff builds up in the HEs but I don't know anything about the difference between salt/fresh/brackish. It SEEMS to me that there it builds up faster here in the Ches bay than it did on Long Island Sound but I didn't really look scientifically at it. I just don't remember having to do it much up there.

I do know that even the slight bit shown on the "before" HE picture affects WOT temps of our engines when running for extended periods. When clean, as shown in the after Pic, I have run the engines at WOT for an hour out on the bay with the temps holding at around 178-180.

Yes, the cleaning using the DD method takes literally 2 minutes. Of course, the disassembly/reassembly takes a few hours!

[SEVEN]

I'm surprised the surveyor required a cleaning of the HE. They look better than most I've seen.

[Entonces]

Mike, thanks for the post. I will have to check mine when i get home off my ship. My SME has been running up on temp (Ok, I have not left the dock in a few months but hey, I'm intending to!) & unknown last time the HE was cleaned!

[MikeP]

As far as the acid mix, DD says 1/3 muriatic, 2/3 water plus 1/2 lb of Oxalic acid to each 2 1/2 gallons of the solution. 3 gallons total is sufficient in a typical 5 gal bucket but that will not cover the HE so you will have to lower the HE, wait a minute, then upend it, wait another minute. OR make 5 gallons of solution which will cover the HE completely.
I have to admit that I have cleaned them with and without the oxalic acid and can't see any VISUAL difference.

FWIW, the engine surveyor said the THE WAY to clean HE's nowadays is ultrasonically. Whether that's an environmental thing or an actual improvement in cleaning, I don't know. I suspect it's environmental; I can't see how ultrasonics could clean any better although if there are deposits that are not affected by the acid, ultrasonic cleaning could remove them.

[Dan Mapes]

So why pull them off the boat when you can circulate the mix with a small bilge pump? I can see pulling them every few years or so to paint but the "Genesis method" has saved me tons of grief plus it boils out all of the oil coolers as well.