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  Topic Review (Newest First)
11-07-2011 09:42 AM
RichH RydLyme is a *buffered* hydrdochloric acid. The buffering agent prevents the reduction of the normally formed protective 'black' (ferrous) rust into destructive 'red (ferric) rust ... so that you can descale the carbonate formations ... and with minimal attack of the engine's base metal. Simple speak: RydLyme and other buffered descaling agents remove the 'insoluble salts' but not (much of) the 'metals'. Straight unbuffered HCl will bore through the carbonates, through the 'rust' and into the metal ... and since cast iron is typically a 'stratified' casting (like an onion) once you penetrate one of these 'onion layers' you promote 'slab rust' - large 'plateletts' of ferric rust that can loosen and migrate further into the engine and exhaust manifold and can cause partial or total blocking of the cooling circuit.

Oxalic is 'too weak' an acid to adequately react with the formed carbonates .... the 'reactivity' of oxalic vs. carbonates will require an immense amount of 'oxalic' or 'vinegar' to do the job.
11-06-2011 01:27 PM
mitiempo Rydlyme is hydrochloric acid based with added wetting and penetration agents. I will be trying it on my Yanmar in the near future.
11-06-2011 10:20 AM

Saildrives have a reputation for restricting cooling water flow due to growths
and need to be cleaned out from time to time.
11-06-2011 10:08 AM
LakeSuperiorGeezer Engine corrosion is complex. Look at this: Corrosion in Salt Water Marine Engines
11-06-2011 06:15 AM
Rydlyme for Yanmar cooling systems

Rydlyme is the preferred choice for Yanmar cooling systems.
Too strong an acid will eat the exchanger and you'll find yourself with an expensive part to buy.

The heat exchangers found on Perkins,Universal and Westerbekes are much more durable.

However more care is needed on Yanmar Heat Exchangers

I prefer to dissasemble the heat exchanger.
Physically remove all blockage then soak in Rydlyme.
Works every time
11-03-2011 03:58 PM
raranovich Just the answers I was looking for, I have the same problem in a Yanmar 2QM20 I am rebulding. Will try to descale it with oxalic acid.
11-03-2011 10:07 AM
jkimberly +1
10-29-2011 03:35 PM
Capt Len Good advice doesn't improve with age but neither does it deteriorate.I find these old threads a good read.
10-25-2011 05:28 PM
JimsCAL Ah well. Fooled again!!
10-25-2011 12:56 PM
Originally Posted by treilley View Post
Thread is over 8 years old. hopefully solved by now.
Good Point!!
This thread has more than 10 replies. Click here to review the whole thread.

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