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Descaling Yanmar 2cylinder raw water system

Avi

.
Sep 23, 2018
24
S2 9.2c Palacios tx
I need to descale my 1979 yanmar 2qm15 . I have a raw water cooling system. How exactly I do it? Can anyone explain to me the process?
Can I use a mix of vinegar or it has to be a specialty marine descaler solution.
Thanks
 
Aug 12, 2020
51
Lancer 36 Pago Pago
I used muriatic acid on mine, but i had the head off already, and mine was completely plugged due to the previous owner ("when was the last service done?" "Huh?") If you drain your system using the draincocks , then pull out your thermostat and pour in a 25% muriatic solution with water and let it sit for a while (15 min or a bit more) with the seacock closed, then reinstall the thermostat, connect everything, open the seacock, and run it until the engine is warm, it will flush it out. Repeat as needed; I think the operations manual says once a year. If you can find the operators manual online it will have the exact procedure which the above should be similar to.:cool: Use eye protection when mixing the acid; vinegar is too weak imo, and the pro descalers are overpriced compared to muriatic.
 

BobM

.
Jun 10, 2004
3,269
S2 9.2A Winthrop, MA
If you are on the hard, leave the thermostat out until you are done flushing, as you won't be able to run the boat all that long. Some pH paper is handy to be sure you are back to neutral too.
 

Avi

.
Sep 23, 2018
24
S2 9.2c Palacios tx
Thanks for the advise I already did it, I think it’s successful, haven’t used the engine much yet