Descale an en­gine

Mark Ryan demon­strates how he cleaned the raw wa­ter pas­sages on a Yan­mar 2GM20 with the use of Ryd­lyme

Practical Boat Owner - - Contents -

Mark Ryan cleans out his Yan­mar

The ven­er­a­ble, hardy Yan­mar 2GM20 on Tri­ola, my muchloved 30ft 1970s Al­bin Bal­lad, was in­stalled long be­fore I owned her, likely in the mid-’90s: I have never been able to track down the ex­act date. Through all sorts of chal­leng­ing con­di­tions, the en­gine has never let me down.

Ev­ery year, I du­ti­fully ser­vice the en­gine: how­ever, in those ser­vices I had never in­spected the ther­mo­stat. So, upon notic­ing some rust around the ther­mo­stat hous­ing, I fig­ured it was high time to get the ther­mo­stat out. On its re­moval, I was con­fronted by a very crusty and sor­ry­look­ing af­fair. Peer­ing down some of the raw wa­ter pas­sages, I noted that about 20% of the open­ings were blocked with salt and scale de­posits.

This can lead to poor cool­ing per­for­mance, even­tu­ally re­sult­ing in over­heat­ing and dam­age to the en­gine. Much Googling fol­lowed, as well as many posts to the beardy, sage and salty seadogs of the PBO fo­rums – and, as a re­sult, I dis­cov­ered Ryd­lyme. Ryd­lyme is a non-toxic, biodegrad­able so­lu­tion that uses some form of chem­i­cal wiz­ardry to re­move scale as well as ‘rust, mus­sels, bar­na­cles, ze­bra mus­sels, tiger shells and other wa­ter-formed de­posits’.

Fig­ur­ing out your cir­cuit

Now we have our Ryd­lyme, we need to fig­ure out the route we need to pump this through our en­gine, and make sure that the so­lu­tion reaches ev­ery part of the en­gine it needs to. The raw wa­ter flow­ing through our hardy lit­tle en­gine will take one of two routes. If the en­gine is cold, the ther­mo­stat will stay closed to help the en­gine get up to op­er­at­ing tem­per­a­ture and the wa­ter will flow through the by­pass.

Once the en­gine tem­per­a­ture rises, the ther­mo­stat will open and close as re­quired to let the raw wa­ter move around the en­gine to cool it down (and this is the area we want to descale the most).

With this in mind, sim­ply tak­ing out the ther­mo­stat and pump­ing the Ryd­lyme through the en­gine will likely favour the by­pass and not ac­tu­ally flow through our en­gine at all, re­duc­ing the ef­fec­tive­ness of the treat­ment dra­mat­i­cally. The so­lu­tion to this, once the ther­mo­stat is out, is to clamp off the by­pass hose to force the liq­uid through the en­gine it­self. I only had

a stan­dard G-clamp avail­able: how­ever, it is ad­vis­able to use a proper hose clamp as that will be less dam­ag­ing to the hose.

Pump the Ryd­lyme through your en­gine

Now that we have our plan and a method to pre­vent our Ryd­lyme by­pass­ing the en­gine en­tirely, it’s time to set up the cir­cuit. The Ryd­lyme is cir­cu­lated us­ing a small 12V sub­mersible pump. n Re­move both your en­gine an­odes (there is one in the head and one in the block) or else th­ese will get gob­bled up by the Ryd­lyme. n Re­move your wa­ter pump by un­do­ing the bolt and pivot bolt hold­ing the wa­ter pump on. (Pic­tured right) n Re­move the im­peller from your wa­ter pump by un­do­ing the tiny bolts on the back-face plate and tak­ing it out with ei­ther an im­peller re­moval tool or a cou­ple of screw­drivers, be­ing care­ful not to dam­age the hous­ing. Put the plate back on, mak­ing sure that you re­place the bolts in the cor­rect or­der. n Take the in­let pipe off the wa­ter pump and at­tach your hose pipe and lit­tle 12V pump with a Ju­bilee clip. n Re­move your ther­mo­stat. Be very gen­tle with the two bolts that hold the hous­ing on – if you shear them off, you will be in a world of pain. (This I know at first-hand!) n Re­place the hous­ing with­out the ther­mo­stat in it.

n Take the pipe off the top of the ther­mo­stat hous­ing which goes to the ex­haust el­bow (or, more likely, the anti-siphon valve) and put a pipe on here, with a Ju­bilee clip, back into your bucket. n Clamp off the by­pass. n You are all set! Your cir­cuit is com­plete. n Next, we mix up our Ryd­lyme: one part wa­ter to one part Ryd­lyme. I am in­formed that the tem­per­a­ture of the wa­ter has no bear­ing over the Ryd­lyme’s ef­fec­tive­ness. n Start pump­ing, mak­ing sure to keep an eye on your bat­tery lev­els! n If you have any other bits (such as your ther­mo­stat) that need clean­ing, pop th­ese into the bucket and watch them fizz away and clean them­selves up. I also popped my anti-siphon valve in the bucket as it looked as though it could do with some TLC. n Ryd­lyme sug­gest one to four hours, so I ran the so­lu­tion for two hours one way through the block, then re­versed the cir­cuit and ran it for two hours back the other way.

Startling re­sults

The re­sults were startling. All of the raw wa­ter pas­sage­ways were clear, and my old, grim and crusty ther­mo­stat, which I had as­sumed was be­yond any hope of res­cue (I had even pur­chased a new one from French Ma­rine), came up as good as new.

I was now con­tent that my boat’s raw wa­ter pas­sage­ways would be in a good con­di­tion for my sea­son ahead. Job done!

The fi­nal route our Ryd­lyme will take through the en­gine

Cool­ing wa­ter flow­ing through the block with the ther­mo­stat open

Cool­ing wa­ter us­ing the by­pass with the ther­mo­stat closed

ABOVE: By­pass hose clamped

Undo the bolt and pivot bolt

At­tach the hose and the lit­tle 12V pump

Tak­ing out the ther­mo­stat

Wa­ter­ways choked with de­posits

The re­moved ther­mo­stat

The cir­cuit com­plete and ready to start pump­ing. You can pop any other bits that need clean­ing (such as your ther­mo­stat) into the bucket of Ryd­lyme and watch them fizz Pump and re­turn in the bucket, ready to go I also dropped my anti-siphon valve into...

The treated ther­mo­stat next to the new one

The ther­mo­stat be­fore treat­ment

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