Calcium buildup

[FLDAVE02]

I have a circa '93 Yamaha 75 hp two stroke. I'm having a problem with what appears to be calcium buildup in the cooling system causing the engine to over heat. I've removed the therostat cover and the ports are "rocked up". Scraped, brushed and blew out all I could reach. Tillted the engine up and poured Lime away in untill it was filled up to the PCV port. Left it overnight and ran the engine to blowout the crud. Put it all back together and ran the boat down the river. It took longer to overheat than before, but still over heating. I live on a canal off Crystal River (Which isn't anymore) in Florida and the water is quite hard.
Is there a industrial product I could use to desolve the lime and clean out the engine?


TIA, Dave

[robert graham]

You could run your motor in a 55 gallon drum of water with Saltaway or similar mild acid...trick is to dissolve the calcium/mineral deposits without dissolving the aluminum motor. And you don't want chunks or pieces of deposits breaking loose and possibly plugging small passageways in the motor. I spent 13 years in water treatment/acid cleaning/de-scaling of cooling systems, heat exchangers, etc., so it can be done, but there will always be a risk of damage to the metal parts. Check out that Saltaway for more information on flushing your system. Good Luck!

[FLDAVE02]

Calcium buildup

Thanks Bob. I work at a Nuclear Power Plant that uses once-through seawater cooling. We use a product called Chlor-rid for dissolving salt residue.
Because of the large crystal chunks of "scale" I found under the thermostat housing, I'm going to remove the intake and exhaust covers and "pick and clean" what I can reach. Then, let it soak with Chlor-rid. The funny thing is, I've had this engine since new '94ish and it's only been in the last year that this problem has developed. Just from observation about 75% of the folks around here run Yami outboards. No one else seems to have this problem.
So I'll just treat the symptom until I can determine the cause.

Again, thanks.

[robert graham]

Good luck removing those covers and hopefully none of the bolts break off from corrosion deposits. Might be a good idea to spray/soak all those bolts for a few days with a solvent like PB Blaster or similar to help them come off without breaking. Maybe add some heat to each bolt head with a propane torch?