Engine Flush Procedures

I’m new to diesels and new to boating year round in warm Florida water. I have a few questions on engine system flushing. I have a (new to me) 1998 Mainship 350 trawler with a 2008 Yanmar 6YLP-STC 370 hp engine. I was replacing the raw water impeller and decided to pull off the cover to the intercooler(?) and noticed a lot of debris; barnacle shells, rubber, even some old zinc pieces. Looks pretty clogged up. I have been reading a lot and watching YouTube but still not sure how to do this.

Here are a few questions:
Do I flush before the impeller or after? Please don’t tell me I need to remove the new impeller. I’ve seen BB (Barnacle Buster) use a funnel over the sea strainer. I don’t have a sea strainer for the engine, just a grate over the hull intake. Do I need to install one?

Some videos show it going into the strainer and thru the engine components and letting the solution sit in the system for a couple of hours then flush it out with sea water. Also have seen videos with a closed loop flush which I’m guessing is more effective. I can figure out a way to get it into the intake hose but where do I close the output of the loop on the exhaust or hot side or before it goes into the muffler?

Haven’t used the boat much since purchased earlier this year because I have been learning and retrofitting much of the boat. Every time I learn and fix something I uncover another issue. Yes I know, it’s a boat. Thanks in advance.

I have used barnacle buster in my engines once last year. My impeller on the starboard engine is just short of impossible to remove and replace so I did not want to do the recirculating method and instead went the suck it in and leave it for about 7 hours. I do have a strainer so I used a Sea Flush adapter to get the BB into the engines, very simple. My temperatures went down 5 degrees on one engine and 10 degrees on the other engine.

I'm a believer in Barnacle Buster. I used the recirculating method. I took a trip to the plumbing store and made a couple of hose adapters that connected from a spare bilge pump to the hose to the raw water pump and another adapter that connected from the hose off the output from the heat exchanger back to a 5 gallon bucket with the bilge pump in the bottom. Filled it with Barnacle Buster and let it run for about 5 hours. At the end of the process the heat exchangers looked like new.

I had the same engine on a previous boat. Looks like you have already cleaned out the debris on the exchanger inlet which is essential to assure good acid flow through all tubes. BTW that is the main cooling exchanger.


The next thing you should do is service the aftercooler which is on the starboard side of the engine. You need to remove, disassemble, clean both sides particularly the air side, reassemble with new o-rings and lots of grease and then pressure test it. The pressure test assures that there are no air side to water side leaks which could ruin your engine if you acid flush.


Then hook up a recirculation loop using a small bilge pump in a bucket. Hook up the pump's discharge to the main heat exchanger by removing the hose to the raw water pump and adapting with pvc fittings. Disconnect the water hose that normally goes to the injection elbow and use it as a return to the bucket. Remove all zincs and replace the brass plug and pinch off the raw water hose to the packing gland.


Circulate for a couple of hours using a 50/50 mixture. Then flush with fresh water, reconnect and run the engine for ten minutes to get the last of the acid solution out.


Here is a pic of the connection to the main heat exchanger:

Great, clear summary, Dave. I assume that terminating the flush point just before the injection elbow would allow the oil and gearbox coolers to be included in the flush for engines set up that way? Like Lehman’s?

Djoub said:

Here are a few questions:
Do I flush before the impeller or after? Please don’t tell me I need to remove the new impeller. I’ve seen BB (Barnacle Buster) use a funnel over the sea strainer. I don’t have a sea strainer for the engine, just a grate over the hull intake. Do I need to install one?

Some videos show it going into the strainer and thru the engine components and letting the solution sit in the system for a couple of hours then flush it out with sea water. Also have seen videos with a closed loop flush which I’m guessing is more effective. I can figure out a way to get it into the intake hose but where do I close the output of the loop on the exhaust or hot side or before it goes into the muffler?

Click to expand...

Can't speak to your engines, but I've flushed with Rydlyme using both methods: recirculate, or fill-and-wait. Didn't see much difference in outcome, but that may have been a function of going-in state, too...

For the recirculate method, I used several purpose-made hose/fitting combinations, and a transfer pump... and had to remove the impeller since I wasn't using the engine's raw water pump. This was coincident with time to change impellers anyway, so I just waited until afterwards to install the new one.

For the fill-and-wait method, I used some of the same hoses/fittings and injected solution (using the transfer pump) from a different point, didn't have to remove the impeller.

Dripless shaft seals can be a drain point, if you have those. I didn't figure out an elegant (read: easy) way to bypass ours, so I kept losing solution during the recirculate method. In fact. that's why I took the fill-and-wait approach on the other engine.

We have sea strainers, and Groco flush adapters just before the strainers... so during the recirculate method, that sea strainer got an extra cleaning, too. That was just coincidental, though; presence (or not) of the strainer was mostly beside the point when it came to flushing the rest of the raw water system.

I had to remove zincs, first, 'cause Rydlyme will eat 'em. I think BB will do the same. (I've used BB for AC raw water system, later, and it seemed to work about the same as Rydlyme.)

The point about aftercoolers needing periodic off-engine service is also specifically pertinent for our situation; flushing our raw water system is in no way a substitute for real aftercooler service... 'cause on-engine flushing does nothing for the air side of the aftercoolers.

-Chris

Dave’s flush method is spot on. Well worth the effort. Will work on all your friends boats with different hose size adapters.

I flushed with soda ash or baking soda to neutralize when done with the BB and before filling with coolant.

angus99 said:

Great, clear summary, Dave. I assume that terminating the flush point just before the injection elbow would allow the oil and gearbox coolers to be included in the flush for engines set up that way? Like Lehman’s?

Click to expand...

Yes, the main heat exchanger is the first element in the flow path after the r/w pump and the injection elbow is the last, so all in between will get flushed.

I forgot to mention that it is essential to remove the r/w pump to get to the elbow hose to the main heat exchanger. Sorry, I know it is a real PITA. Also if you look closely at the pic you will see where the r/w pump bolted up I put a small piece of vinyl siding shingle to keep any splashes out of the engine.


BTW a soda ash rinse afterwards is good but not essential. Running the engine for ten minutes at idle pumps dozens of gallons of r/w through the system which will get the last of the acid out.


David

Thanks everyone, this helps. I’m hoping that I can pop off the small 45 degree hose from the end cover of the main cooler and attach the input of the flush to it. I also saw a video where the person replaced the cooler cover with a piece of clear plastic and attached a small hose fitting to it. This avoided having to go thru the raw water pump removal and being clear he could see how it was working.
Guess I’m off to the boat to get some measurements and then to the plumbing store.
Thanks again for your help! I will post pics after the flush is done.

Replacing the heat exchanger inlet cover with a flat plate won't work. That is because there are baffles inside the cover that direct the inlet flow down one of three passages in the heat exchanger.

From the first pass the flow goes to the tranny cooler, the aftercooler, the lube oil cooler, then back to the main heat exchanger for the final two passes and then to the injection elbow.

A simple plate will not have baffles so the flow will be all screwed up. The rubber inlet elbow is the best way to hook up to acid flush that engine.

David

If you look at the MSDS on both one will be hydrochloric acid and one will be phosphoric acid.

Hydro is cheaply bought in hardwares as brick cleaner.
Phospho is cheaply bought as salt water pool filter cleaner.

Personally, if I had the end cap off I'd simply rod it out.

I was struck by the OP mentioning that he didn't have a sea strainer, but just a grate over the intake? That seems problematic to me, but I'm ignorant of all things internal combustion. What do your more informed folks think?

Here’s the link to an article on flushing, I think your same same engine, by Dave D. from the Forum Library.

http://www.trawlerforum.com/forums/...0196-cbf175b78c87ea5c6f62578ab279f840f2e174fa

Larry M said:

Here’s the link to an article on flushing, I think your same same engine, by Dave D. from the Forum Library.

http://www.trawlerforum.com/forums/downloads.php?do=file&id=71&act=down&actionhash=1542310196- cbf175b78c87ea5c6f62578ab279f840f2e174fa

Click to expand...

I am the author of the referenced article above. I had forgotten about it (hey senior memory) and post #4 above is a quick summary. If you can't get there by clicking the link, and I can't because it gives me a security token error message, click on Library at the upper right of this page and the Misc section to find the article.

David

dhays said:

I was struck by the OP mentioning that he didn't have a sea strainer, but just a grate over the intake? That seems problematic to me, but I'm ignorant of all things internal combustion. What do your more informed folks think?

Click to expand...

I have always had internal strainers on my boats and once paid extra to have it installed on a new boat- Mainships didn't include them as standard. But I wouldn't swear that it does any good. The passages on the underwater strainer are small enough to trap anything that would affect the r/w impeller or get clogged up downstream. I have rarely picked up anything in the inside strainer that the external strainer didn't trap out.

But it does seem like a good idea. Also it is an easy place to hook a fitting for a fresh water flush or to introduce pink antifreeze in the top when winterizing your engine.

David

You need a strainer. Sea grass, especially likes to come in and ruin your impeller. If it gets by the impeller then it clogs the heat exchanger. Bigger boats use dual strainers so you can switch and clean while running.

There is someone on the forums that put a strainer after the sea water pump to catch broken impeller pieces. Not a bad idea.
The easy way to flush is to install fittings that are plugged or valved off when not in use. Also hot solution works much faster and better than cold.

I prefer Rydlyme. It works as well as others and is biodegradable, so is legal to pump over the side in most places. Rydlyme is good to 180°F, so I do it hot with the engine idling and watch coolant temps. And I pull my engine zincs.

Don't forget to do the coolant side flush every few years. Some people never do it and chase overheat problems in the sea water side when it's the coolant passages that are the problem.

OK, one step forward, one back.

Dave, we have the same engine but different boat. Found the article in library, thanks.
Yes to the baffle on the cover, when reinstalling it the gasket looked weird, like it was puffed out in places? is this the baffling you refer to? Also the V sticker just below the zincs looks like an alignment mark for the cover. Being round and a single bolt I would think there would be some sort of “key” but couldn’t find anything other the the V and a mark on the cover side. BTW, I like the strainer you have in the article picture, is that a fresh water flush adapter?

I purchased 2 90 deg, 1 1/2 rubber elbows to attach to the exchanger, adapters to connect them to the bilge pump in the bucket. Still need hoses, I have some new leftover sanitation hoses, will these work until I find something more permanent?

As far as the strainer goes, I thought it was weird not to have one for the engine. I have 3 smaller ones for AC, gen, head(not used). It would be easy to install one and I would also add another valve before the strainer as the sea cock is pretty hard to get to, almost in the rear bilge of the engine room. Wouldn’t want to try to get to it at sea with a hot spewing engine. This will be a future project.

One last item, this tee and valve is on the output of the exchanger before it goes into the exhaust elbow. Small stream of water goes to a port thruhull. Someone said it was installed to adjust/maintain back pressure and temperature in the muffler. This won’t be in the flush loop but just curious what it is for.

“The more I learn, the more I realize how much I don’t understand” Einstein.

I would also want a strainer. Some boats only have the exterior screens and get along ok, but it would be my luck that I would suck a bunch in through the screen. A straine will catch the stuff.

Don't know what it's for, but a brass gate valve doesn't belong on a boat.

On a related note, is a Barnacle Buster flush harmful to impellers?

BB doesn't seem to have harmed the impeller in our AC raw water pump... and Sew Clean (another Trac product, same acid, slightly different dilution, recommended for sanitation hoses) didn't seem to bother anything in our toilet (including the "rubber" joker valve, etc.)... but those are the only things I've used the stuff in.

-Chris

It didn’t seem to bother mine.

Larry M said:

Here’s the link to an article on flushing, I think your same same engine, by Dave D. from the Forum Library.

http://www.trawlerforum.com/forums/...0196-cbf175b78c87ea5c6f62578ab279f840f2e174fa

Click to expand...

Larry, I wasn't able to use this link because "a security token was invalid" (?)

Heron said:

On a related note, is a Barnacle Buster flush harmful to impellers?

Click to expand...

No, the impeller is rubber which acid won't hurt. It does have a brass spline insert but the corrosion rate is too small to be noticed.


But a raw water pump with the impeller in place won't let much acid through. You need to pull it if you plan to hook up a circulating pump upstream of the r/w pump. If you plan to let the engine drive the pump then the agitation might do some corrosion damage to the brass insert.


You didn't ask about the r/w housing which is bronze and acid won't hurt it much. But the shaft might corrode a bit as it is SS.


All in all, it is better to hook up after the r/w pump.



David

Heron said:

On a related note, is a Barnacle Buster flush harmful to impellers?

Click to expand...

No, the impeller is rubber which acid won't hurt. It does have a brass spline insert but the corrosion rate is too small to be noticed.


But a raw water pump with the impeller in place won't let much acid through. You need to pull it if you plan to hook up a circulating pump upstream of the r/w pump. If you plan to let the engine drive the pump then the agitation might do some corrosion damage to the brass insert.


You didn't ask about the r/w housing which is bronze and acid won't hurt it much. But the shaft might corrode a bit as it is SS.


All in all, it is much better to hook up after the r/w pump.



David

DDW said:

Don't know what it's for, but a brass gate valve doesn't belong on a boat.

Click to expand...

Why no brass gate valve? I think I read something about this in another post. Is it the valve getting clogged or corrosion?
I don’t want to mess with it now but could be a future project.

Ken E. said:

Larry, I wasn't able to use this link because "a security token was invalid" (?)

Click to expand...

For some reason it didn’t copy right.

It’s in the Forum Libray, up right corner on any page, Miscellaneous Category, title: Acid Flushing Your Engine. Credit goes to Djmarchand.

Djoub said:

Why no brass gate valve? I think I read something about this in another post. Is it the valve getting clogged or corrosion?
I don’t want to mess with it now but could be a future project.

Click to expand...

Same thing with the reducers on the bronze tee that appear to be machined brass. If they're bronze, they'll be cast, not machined. Additionally, the brass gate valve is inappropriate for use in that application. It should be a ball valve, and it should be bronze or non-metallic.



Never put brass in contact with seawater. Brass is an alloy of copper, tin, zinc, and lead in varying ratios. If you're familiar with electrolysis, you know that very rudimentally it's the corrosion of dissimilar metals in an electrolytic solution. The seawater is the electrolytic solution. With brass in seawater, the different alloys that comprise the brass itself become the dissimilar metals, the seawater is the electrolyte. The less noble metals, namely zinc are dissolved out of the alloy. At some point, it loses structural integrity and simply crumbles. If it's below the water line, use your imagination.



Any corrosion or verdigris that's pinkish is a telltale for dezincification. It can occur without a lot of outward evidence, and progression of the process can vary with the alloy. So, mess with it now, get rid of the brass!

So quick update post flush,
After everything was hooked up, I ran straight water thru the loop, maybe 3 gallons in the bucket. Then added almost a gallon of consentrated BB to the bucket. Within a few minutes it started to foam and overflow the bucket. Don’t know if it was a reaction or if it opened up passages that were clogged. It did subside after a while. The flush also opened up a draincock that I couldn’t get to stop dripping. A pencil worked good to temporarily plug the hole until after the flush. All zincs were removed except one, it was tough to get to and I was running out of daylight. I removed and replaced it the following day and it was pretty deteriorated.
As you can see in the picture, a big difference. Can’t say the impact on the cooling tempature since I haven’t had the boat long enough. I also did the AC strainer, although I did not circulate. Much bigger stream on the output.
Thanks for the guidance and information.

Here’s the pics