1GM Yanmar Scale buildup and Prevention questions

[Skipjack]

I've got a couple of questions.

My engine is raw water cooled and has built up some scale around the cylinder head. Its not a problem right now but I just want to have a clean bill of health for my Yanmar. How do I remove this scale? I did some research online that suggested an acid treatment. A buddy at the marina said that was a huge mistake however he couldn't defend when I asked why or the logic behind it?

As far as I am concerned I had planned to take some samples of the scale and make some acid solutions at home and see what dissolves the scale and then just let the acid sit overnight in the water cooling passages.

(1st Question)
Is there a good process for removing scale in a raw water cooled engine?

(2nd Question)
To prevent scale buildup do you think it would be worth it to rinse the engine with fresh water after every use?

I could install a tee into my freshwater tank line with a valve to open or close fresh water that would divert fresh water into the cooling system. When I got back to the dock, just open the fresh water valve and close the sea cock and run fresh water through the engine for a little bit with the engine running. I am already down in the engine room to close my seacock anyways?

Probably would be an effective way to turn over my fresh water in the fresh water tank. Sometimes that fresh water may sit for 2 or 3 months without use.

[Joe Myerson]

(1st Question)
Is there a good process for removing scale in a raw water cooled engine?

There are a number of de-scaling products on the market. One of my former associates (now the editor of Practical Sailor) suggested that I use one of them at the end of the year, running it through the cooling system and then flushing it with water before winterizing my 1GM. I have never done so to date.

(2nd Question)
To prevent scale buildup do you think it would be worth it to rinse the engine with fresh water after every use?

I've never thought about doing this, but it certainly couldn't hurt. After all, outboard manufacturers advise flushing their cooling systems with fresh water after use in seawater. (I'm not sure how many outboarders actually do this on a daily basis.)

Good luck.

--Joe

[Duncan]

Is there a good process for removing scale in a raw water cooled engine?

I believe there are quite a few, in fact, but I have heard that citric acid offers the best blend of effectiveness with low toxicity. Muriatic acid is also suggested, but this can be quite strong, depending on how much you dilute it.

To prevent scale buildup do you think it would be worth it to rinse the engine with fresh water after every use?

My (YSE8) engine is set up this way. I haven't been flushing it, since I am on a mooring and in fresh water. I imagine this might be a good idea, though, for someone in a slip on salt water.

[Ray Garcia]

I've read two sides to the story on descaling a raw salt water cooled engine. One it is very beneficial to keep those cooling passages clear so they can do there job. On the other hand the engine can be rotted from the inside out over time with too harsh descaling treatments.

Here is what I do. I winterize my YSM8 with a thorough flush of clean water and then the antifreeze. In the spring time a few weeks before launch I start the motor and flush with fresh water. I then introduce white vinegar into the motor though a bucket with a hose attached to the water inlet on the engine. Once the vinegar is in there I remove the zinc plug and call it a day and go home. The bubbling starts immediately and I know the carbonate is being broken down. If you do it yourself make sure you let that CO2 gas vent. Not sure I would want to find out what could happen if you don't. The following weekend I go back and flush the motor with fresh water, replace the zinc and finalize my tasks before launch.

Does it help? I guess I really won't know until the motor is pulled and disassembled. But I know it can't hurt. The YSM motor is designed to run cooler than a closed heat exchange cooling system. With this design you definitely do not want to run the motor over its optimal temperature range. The scale will precipitate faster from the hot water in the cooling passages when you do. With all the motoring I've done, overheating has been the least of my problems.