Rydlyme cooling system clean

[Jon Tallis]

Thought I'd share my experience of cleaning the cooling system of my 2001 150HPDI with Rydlyme.
Engine is flushed religiously with fresh water after every use but on removing the thermostats I noticed there was s significant buildup of salty crud.
Having done a bit of research on cleaning methods (vinegar, citric acid etc) I opted for Rydlyme - largely because this is precisely what it is formulated to deal with.
I did the job when the lower unit was off for its annual impeller & oil change.
Cleaning setup involved a plastic tub under the engine leg with a 50% mix of Rydlyme & fresh cold water (would have preferred hot water but couldn't figure out a way to achieve this. 1400lph submersible pump from Amazon in the tub, connected direct to the engine water tube. Thermostats removed and tell-tale tube blocked up (intermittently un-blocked to get then flushed too). Thermostats dropped into the plastic tub to get those clean too.
Circulated Rydlyme for 4 hours, then flushed twice with fresh water for 1 hour each.
Very impressed with the results - cooling passages are now pretty much like new and the plastic tube collected a good 1/4 of a cup of solids (sand etc).
Rydlyme is pretty costly (£65 a gallon), but I recon this is something I'll defintely repeat every year or two to keep the cooling tip-top.
I didn't take any "before" photos :-( but have attached some after photos including a borescope photo down one of the cooling passages and a photo of the pump I used

[beamishken]

You do realise Rydlyme is basically hydrochloric acid (brick acid) which you can buy off ebay & dilute yourself for a 1/10th the cost?
Check out the msds sheet & it tells you the concentration less than 5% iirc

[Limecc]

Thanks for the write-up I'd never heard of it.
Don't forget Saltaway's main ingredient is Sulphamic acid.

Citric acid or acetic acid/white vinegar (as you say) could also work nicely, also Oxalic acid which although more expensive, doubles up to be used on a fibreglass hull to bleach and remove discoloration and mud stains.

An acid is needed to dissolve metal salts that are insoluble in fresh water. I think de-ionised water would be a good flushing agent, but not as effective or cheap as using an acid.

All acids easily obtained via Amazon.

[Jon Tallis]

Originally Posted by beamishken

You do realise Rydlyme is basically hydrochloric acid (brick acid) which you can buy off ebay & dilute yourself for a 1/10th the cost?
Check out the msds sheet & it tells you the concentration less than 5% iirc

I do, but it also has corrosion inhibitors added and is formulated as a marine engine descaler hence I was happy to pay the premium for a purpose designed product.
Brick acid (HCL), citric acid etc are all much cheaper options but all will attack metal components to a greater degree than the same product with a corrosion inhibitor added, which is what Rydlyme (and others) are.
The MSDS contains safety-relevant data only, not an exhaustive list of ingredients