Muriatic Acid Flush for 315 Yanmars?

[CHolgerson]

Hello Faithful,

It has been a while since I have posted last but I am constantly lurking. Dad still has the boat and has been using her a lot since his retirement to Delaware. I just recently got married and am in the process of rebuilding a 1975 23' Chris Craft Lancer with my father in law, back on Long Island, NY.
My Dad is running 6LP-STE 315HP Yanmars in a 31 Bahia Mar. He has around 800 hours on them and about 5 seasons. He noticed that they are running a little bit warmer than normal (200 deg). He replaced the raw water pumps last season. Is it normal maintenance to flush the heat exchangers with muriatic acid and if so are there any gaskets that need to be replaced after the flush? Thanks for any help.

Best Regards,
Chris Holgerson
"Priceless"

[Bruce]

chris,
Yes they can be flushed but do it off the engine.

There are the two end cap gaskets that are rubber and should be replaced along with the zinc pencils.

Pull it off and give it to a radiator shop that does heat exchangers. I don't do my own anymore.

I drop it off, they clean it, pressure check it, replace the gaskets. All I have to do is paint it. They do it for less than a couple of my labor hours, much less than I can do it for and I don't have to worry about messing with muriac acid or how to dispose of it properly.

Don't forget the other two raw water coolers on that engine, the oil cooler and the inter cooler. If ones dirty, the others will be also.

Hotter than normal oil and intake air will reduce power and engine life.

Oil cooler has gaskets like the heat exchanger, inter cooler uses orings.

[Brewster Minton]

Not that I really know very much but also check the air cleaner to make sure it is really clean and does not have a lot of dust on it.

[Bruce]

If its the factory foam filter, they usually fall apart before they get clogged.

Yanmar fell asleep in the air filter design class.

Those foam filters just plain suck and for the 12 bucks cost, they get replaced every year.

[CHolgerson]

Thank you Bruce, I was hoping that you would reply.

Brewster,
When are we going to go out and kill some fish together? I am ready for another session with the tried and true fish club :)

[Bruce]

Btw if the oil and inter cooler are removed also, there are two gasket for the inter cooler, one for where it mounts to the intake manifold and one underneath that is used as a spacer that two bottom bolts go thru. Its a 1/2 wide and about 4 inches long. Don't forget that one.

Watch also how the intercooler tube bundle comes out. The end caps are not interchangable as one end of the tube bundle, remove from housing for cleaning, has a flange.

Also on the oil lines to the oil cooler, use two wrenches when removing and installing the lines. The soldered flanges will not hold up to the torque and will crack without two wrenches.