Hi all. First time on here. I've got a Nordic 21 Cabin Cruiser with a Bukh DV24 (raw water cooled). Runs nice a smooth but overheats at half throttle. My guess is it's pretty gunked up with salt etc (old bloke I bought it off 6 months ago didn't use it much). I've read a few good posts on here about guys using Rydyme, HCl, SaltX to flush it out... so I plan on doing that in the next few weeks. But first I had a couple of questions:

1. Which method would you guys recommend... the pump it through method, or the pour in and let it sit method?

2. Bukh say there's a rubber o-ring wet-liner for the cylinders and anything more harsh than vinegar may damage it. Has this ever actually happened to anyone and is it a real concern? It seems to be mentioned a bit but I can only find posts from people saying they've used acid to flush and haven't had any issues afterwards.

Thanks in advance for any help!

I've used vinegar and it worked. After the engine was warmed up (i.e. end of weekend) I took off the inlet hose and put it to suck up vinegar - a few minutes and no more than 2 - 4 litres, and then turned off the engine. Vinegar is a mild acid. Maybe I did that treatment a few times over the course of a month or 2.
Rydlyme, from what I've read, is also mild and works. Others here use common products from Bunnings, but I forget the names.

Do a search on Youtube for BarnacleBuster videos. Barnacle Buster is just a phosphoric acid mix sold to boaters at exorbitant prices! I use Metal Gleam made locally. It is just a cheaper version of barnacle buster, about 1/5 the price. Rydyme is just another expensive phosphoric acid mix. CLR is another readily available weak phosphoric acid mix. I have done a comparison test using sea shells in mixtures of Metal Gleam, CLR and vinegar and that's the order they performed. The vinegar was particularly slow! Metal Gleam mixed at 5:1 with water was far superior.

Phosphoric acid has no effect on O rings etc.

Phosphoric acid will etch aluminium but everything else just ends up very clean!

Goff,
I have a DV24 too. Had a similar problem. I had a dive under her, the outside of the hull strainer looked clean, barnacle free but found the inside of the hull strainer full of barnacles. Cleaned out, problem gone. The thing is, I didn't notice any difference in the cooling water flow from the exhaust before or after the clean.
Glen from Bukh Taren Point, has recommended the vinegar method to me previously.
Mike

Drop a sea shell into some vinegar and see how long it takes to dissolve!

Did read somewhere that cleaning vinegar is 2 percent more acidic than table vinegar, making it 20 X stronger than table vinegar.
Bunnings sell it

After I get back on my mooring each time I just fill a bucket with fresh water from the flexible shower lead then clip a hose (using Bunnings camlock fittings) to a T valve that I have installed in the intake line whilst closing the water intake cock and suck the fresh water through the motor. Bit of a pain but hopefully it will pay dividends and make the old DV24 last a lot longer.
Installing the T valve also ensures that I could use this same setup as a bilge pump if required.

More preventative than an immediate solution to your problem although would probably clear mild salt deposits over time.

I'll also be interested to see how the cooling system sacrificial anode looks after using this set up since I replaced this (totally disappeared) pencil anode about 9 months ago

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julesmoto said..
After I get back on my mooring each time I just fill a bucket with fresh water from the flexible shower lead then clip a hose (using Bunnings camlock fittings) to a T valve that I have installed in the intake line whilst closing the water intake cock and suck the fresh water through the motor. Bit of a pain but hopefully it will pay dividends and make the old DV24 last a lot longer.
Installing the T valve also ensures that I could use this same setup as a bilge pump if required.

More preventative than an immediate solution to your problem although would probably clear mild salt deposits over time.

I'll also be interested to see how the cooling system sacrificial anode looks after using this set up since I replaced this (totally disappeared) pencil anode about 9 months ago

It's not salt build up you have to worry about but calcium. Cool saltwater running into hot metal causes the calcium build up. Fresh water wont stop it or clear it. Raw water cooled engines will have it around the thermostat area. freshwater cooled will get it in the tubes of the cooler. It will take acid to clear it in both cases or poke through the tubes of the heat exchanger.

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Ramona said..

It's not salt build up you have to worry about but calcium. Cool saltwater running into hot metal causes the calcium build up. Fresh water wont stop it or clear it. Raw water cooled engines will have it around the thermostat area. freshwater cooled will get it in the tubes of the cooler. It will take acid to clear it in both cases or poke through the tubes of the heat exchanger.

Thanks very much for that. I seem to get slow appearance over time of a white deposit all around impeller housing on the outside of the gasket. It does seem to have reduced since I have been flushing the engine but not totally eliminated.
Is this also calcium or is it salt? A bit puzzling as there doesn't seem to be a lesk although I guess there might be some wicking through the gasket.

I just brush it off periodically with a toothbrush. Hopefully it's not an indication of electrolytic activity.

This might not be applicable to you, but I once had a build-up of some sort of minerally-looking stuff within the bore of the CW intake thru-hull.
I had changed everything (impeller, thermostat, hoses) and finally in desperation opened the thru-hull ball valve and stuck a long screwdriver down there. Then, shiver timbers, seawater gushed in bringing with it lots of bits of hard white mineral-like stuff. Very happy engine (and skipper) after that. But ymmv.........

Cheers, Graeme

Thanks all!

I'm going to give it a try with Rydlyme. I know Bukh recommend vinegar but I tried cleaning strength vinegar to remove the salt and calcium from the stuck thermostat a few months ago... it would've taken a month to clean it, so I don't reckon it's got much of chance on the (likely) more gunked up inner workings of the cooling system.

I'll check the intake when I next get a chance, but it was clear 6 months ago, so shouldn't be too bad yet.

@julesmoto I imagine the fresh water flush would help prolong the intervals between acid flushing but I think they're still imminent. And good idea... I might do the same "T" idea and get myself a deck wash!

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goff said..
Thanks all!

I'm going to give it a try with Rydlyme. I know Bukh recommend vinegar but I tried cleaning strength vinegar to remove the salt and calcium from the stuck thermostat a few months ago... it would've taken a month to clean it, so I don't reckon it's got much of chance on the (likely) more gunked up inner workings of the cooling system.

I'll check the intake when I next get a chance, but it was clear 6 months ago, so shouldn't be too bad yet.

@julesmoto I imagine the fresh water flush would help prolong the intervals between acid flushing but I think they're still imminent. And good idea... I might do the same "T" idea and get myself a deck wash!

Rydlyme is now Solverbio and the scale breaker is Hydrochloride-based Descaling Compound and not good for stainless steel. If you use a phosphoric based cleaner you will be able to use it for hull cleaning etc as well. It's also half the price.
Putting fresh water into the system after use wont do anything. The scale comes from hot metal meeting salt water.

I see you are in NSW. If your on the South Coast swing by and I will give you some Metal Gleam. I have used this stuff for more than 40 years.

shop.nowchem.com.au/shop/heavy-duty/metal-gleam/

Excellent for scrubbing down the decks and topsides, shining up SS, passifying SS welds, removing rust and descaling engines.

Because it's dangerous goods Metal gleam 5l delivery cost to Sydney metro is $40 in addition to the $42 cost. Not cheap!

Google phosphoric acid, brew shops sell food grade almost neat. You will have to water it down. Or rust buster from the big green shed, but metal gleam delivered would beat rust buster for value. Tilers use it to clean off grout, that maybe an effective way to buy it. I think I previously posted about using phosphoric acid to remove the remnant zinc from the bronze plug in engine/ heat exchange anode so a new zinc can be simply screwed in

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Ramona said..

goff said..
Thanks all!

I'm going to give it a try with Rydlyme. I know Bukh recommend vinegar but I tried cleaning strength vinegar to remove the salt and calcium from the stuck thermostat a few months ago... it would've taken a month to clean it, so I don't reckon it's got much of chance on the (likely) more gunked up inner workings of the cooling system.

I'll check the intake when I next get a chance, but it was clear 6 months ago, so shouldn't be too bad yet.

@julesmoto I imagine the fresh water flush would help prolong the intervals between acid flushing but I think they're still imminent. And good idea... I might do the same "T" idea and get myself a deck wash!

Rydlyme is now Solverbio and the scale breaker is Hydrochloride-based Descaling Compound and not good for stainless steel. If you use a phosphoric based cleaner you will be able to use it for hull cleaning etc as well. It's also half the price.
Putting fresh water into the system after use wont do anything. The scale comes from hot metal meeting salt water.

I see you are in NSW. If your on the South Coast swing by and I will give you some Metal Gleam. I have used this stuff for more than 40 years.

shop.nowchem.com.au/shop/heavy-duty/metal-gleam/

Excellent for scrubbing down the decks and topsides, shining up SS, passifying SS welds, removing rust and descaling engines.

Thanks Ramona. I appreciate the offer. I'm in Lake Macquaie and already bought the Rydlyme. I've gone with that option because they claim it won't damage rubber at all, and I'm concerned about the rubber o-ring wet liners for the cylinders in the Bukh. They've also got some good info on flushing inboard diesels on their website. The bloke on the phone in WA was actually very helpful too.

Hopefully will get some time in the coming weeks to give it all a crack! Will report back :)

Why would you ever run strait seawater into a cooling system?? Silly Idea bound to fail. So, is there a thermostat? Check that. Otherwise it's a lot of build up, corrosion, and gid knows what. I know nothing about these motors, replace the lot, it would be easyier on the wallet and a lot more reliable.

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Tikker said..
Why would you ever run strait seawater into a cooling system?? Silly Idea bound to fail. So, is there a thermostat? Check that. Otherwise it's a lot of build up, corrosion, and gid knows what. I know nothing about these motors, replace the lot, it would be easyier on the wallet and a lot more reliable.

Well mine is 34 years old. Try that with a Yanmar!

Outboards still do it

Like I said, I dont know about these motors. But how is it possible? As with most things there is always something to stuff it up. Low power for the weight maybe, always so gremlin. Anyway, things improve. Electric is the go. And no reason not to, besides the cost. Not exactly true. At least with this motor you can service, electric?

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Tikker said..
Why would you ever run strait seawater into a cooling system?? Silly Idea bound to fail. So, is there a thermostat? Check that. Otherwise it's a lot of build up, corrosion, and gid knows what. I know nothing about these motors, replace the lot, it would be easyier on the wallet and a lot more reliable.

Never heard of raw water cooling??

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julesmoto said..

Tikker said..
Why would you ever run strait seawater into a cooling system?? Silly Idea bound to fail. So, is there a thermostat? Check that. Otherwise it's a lot of build up, corrosion, and gid knows what. I know nothing about these motors, replace the lot, it would be easyier on the wallet and a lot more reliable.

Well mine is 34 years old. Try that with a Yanmar!

I accept your challenge: my Yanmar 2GM is 40 years old.

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woko said..
Outboards still do it

Good bit of lateral thinking. They are supposed to be flushed with freshwater however after each use. Presumably all the passages are aluminium as well rather than more stable cast iron.

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wongaga said..

I accept your challenge: my Yanmar 2GM is 40 years old.

My rash statement stands corrected :-)

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julesmoto said..

woko said..
Outboards still do it

Good bit of lateral thinking. They are supposed to be flushed with freshwater however after each use. Presumably all the passages are aluminium as well rather than more stable cast iron.

Yes I know the standard is to flush them with fresh water after every trip, and I did. Now I see pro fishers and semis ie boat on river bank chase crabs or outboards used for transport, then there's the outboards on cruising vessels tender, hire boats at the marina, the list goes on . All of the above never flush the motor ?????

Yeah,, I believe it's a myth . I worked on tuna and mulie boats , never was an outboard flushed.
Same goes with my tender outboard ,,never flush it. I set up my Yanmar inboard so I could flush it with fresh water during a vulnerable moment but what a load of ****ing around so I pissed that system off ,, full of compromise to the cooling system. May be if you where to de Commission the engine it may have a very minimal benifit ,,,, may be the benifit is your mental wellness. I have even heard of idiots adding diesel to the flush.

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julesmoto said..
Because it's dangerous goods Metal gleam 5l delivery cost to Sydney metro is $40 in addition to the $42 cost. Not cheap!

... which might be why you can't get it interstate. You won't find it in QLD, for example.

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wongaga said..

julesmoto said..

Tikker said..
Why would you ever run strait seawater into a cooling system?? Silly Idea bound to fail. So, is there a thermostat? Check that. Otherwise it's a lot of build up, corrosion, and gid knows what. I know nothing about these motors, replace the lot, it would be easyier on the wallet and a lot more reliable.

Well mine is 34 years old. Try that with a Yanmar!

I accept your challenge: my Yanmar 2GM is 40 years old.

Bukh, DV36, in its 42nd year of raw water service and still going strong having never been out (4400hr). I used Metalgleam in it 3months ago to give her an internal clean out (didn't know Metalgleam was considered too harsh). My major restriction was internal calcium build up at the flexible hose leading to the exhaust elbow. Didn't want metal gleam in the exhaust so just changed that hose.

A true marine motor, but twice the weight of an equivalent marinised Kubota.

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EastCoastSail said.. (didn't know Metalgleam was considered too harsh).

Who said it is too harsh?

Metal Gleam mixed with water 5 to 1 is not harsh in anything except aluminium. It will etch aluminium at that ratio but is fine for scrubbing aluminium boats if you don't leave it too long. In a Bukh it would last 100 years!

There was a statement above that the Taren Point Bukh distributors recommended against it, due to the wet sleeve liners and the o ring seal for them.
I did about a 25% mix of Metalgleam on a cold engine. Blocked off exhaust discharge and intake, used the calorifier pump to pump through.30 mins and at the end I couldn't see through the clear hose.

Planning to do again soon, as soon as my impeller puller arrives. Also need to tap the thread thread into the block for the anode plug as the thread in the cast iron block is getting worn after 42yrs.