Yanmar 4JH4 engine flush?

rbarkas · #1 (**permalink**) 04-12-2011

I've been thinking about some sort of system to allow me to periodically flush the raw water part of my Yanmar 4JH4 cooling system with fresh water while at the dock. I can envision something as simple as plumbing in a valve with a hose that I immerse in a large bucket that has a fresh water hose filling it.

The reason I may do this is to try to extend the life of the cooling system elbow and other parts that may be affected by salt. Also to try to avoid narrowing of the raw water system by salt/minerals.

Is this a good idea? I haven't heard much about people doing this with smaller Yanmars. If I do this should I consider using some kind of de-salting additive?

Pamlicotraveler · #2 (**permalink**) 04-13-2011

But as soon as you operate it the salt water will be right back in. I'm not sure there is any advantage to doing that kind of flush. Flushing the "fresh water" syatem periodically is advised, but I don't know about raw water.

mitchbrown · #3 (**permalink**) 04-13-2011

Hi there Rbarkus

A fresh water flush is a good idea especially when your boat is laid up for a period of time. I just installed 2 such devices on the 80 foot yacht that i work on (on the 20 KW gensets). All that is necessary is to put a Y valve on the inlet side of the strainer basket which is between the thru hull and the basket. then put a hose bib on one side of the y and the other side goes to the basket. All thats necessary is to connect the dock water hose to the hose bib and flip the Y valve turn the water on and start the engine. Always flip the y valve back when disconnecting the hose so the system is ready the next time you start the engine.

Mitch

treilley · #4 (**permalink**) 04-13-2011

Quote:

Originally Posted by mitchbrown

Hi there Rbarkus

A fresh water flush is a good idea especially when your boat is laid up for a period of time. I just installed 2 such devices on the 80 foot yacht that i work on (on the 20 KW gensets). All that is necessary is to put a Y valve on the inlet side of the strainer basket which is between the thru hull and the basket. then put a hose bib on one side of the y and the other side goes to the basket. All thats necessary is to connect the dock water hose to the hose bib and flip the Y valve turn the water on and start the engine. Always flip the y valve back when disconnecting the hose so the system is ready the next time you start the engine.

Mitch

Be very careful connecting unregulated pressure dock hose. The pressure in such systems can damage the seals in your raw water pump allowing water to get into the engine.

Better to feed the dock hose into a 5 gallon bucket and place a pickup hose into the bucket thus breaking the pressure from the dock hose.

JimsCAL · #5 (**permalink**) 04-13-2011

Pressurizing the raw water system with a dock hose and the engine not running is dangerous. You can back water up into the engine through the exhaust system.

mitchbrown · #6 (**permalink**) 04-13-2011

Good point treille. The pumps in these particular gensets have ceramic seals which are capable of high pressure and an air space before the shaft enters the engine. As far as i know most internaly driven pumps use a ceramic seal. If it is a rubber seal than it could be a problem.

Jim also has a good point. His issue can be handled by simply connecting the hose and turning it on then starting the engine on salt water before fliping the valve to fresh. It would be best to have a shut off valve on the end of the hose so the controls are close at hand. although its been my experiance that not much water gets by the impellar without the engine running. but even so you wouldn't want to leave it on for a long period of time without the engine running.

Mitch