Practical Boat Owner — November 2017

practical engine descaling

What is rydlyme?

DIY

and save

money

T

he venerable, hardy Yanmar

2GM20 on Triola, my much-

loved 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 sorry-

looking 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’.

Engine descaling

Mark Ryan demonstrates how he cleaned the raw water

passages on a Yanmar 2GM20 with the use of Rydlyme

Taking out the thermostat

The removed thermostat Waterways choked with 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

The general ideal of this jollop is to mix

it at a ratio of one part Rydlyme to one

part water and then pump it around

your raw water system. Before you

begin, you must remove all your engine

anodes as Rydlyme will gobble them

up. It is, however, perfectly safe on

most other materials, including (but

not limited to) the following:

Most alloys – The rule of thumb is

that if the alloy is designed for use in a

water system (aluminium engine block

etc), which most marine equipment is,

the alloy should be compatible. If in

any doubt, email Rydlyme’s technical

department (www.rydlyme.co.uk). Also:

iron; HDPE; copper; ceramic;

gelcoats; glassfibre; copper nickel;

PVC; steel; Teflon; plastic; titanium;

stainless steel; painted surfaces;

rubber (seals/gaskets).

I sourced the Rydlyme from the

good people at French Marine in

Brightlingsea, who suggested two

litres would be ample to do the job.

DescalIng an engIne

➜