engine fresh water flush

[sail410]

I have a 315 Yanmar in my 28 albin 2002. It is equipped with a fresh water flush for the engine which I use religiously. I just read an article in the Boat US magazine tech questions section where they recommend not utilizing pressure water to flush but rather a hose into a bucket of water. the engine under question was Yanmar 18. I do the same with my generator and airconditioning. Is there a problem with this procedure? I close the intake valve, start the water, start the engine then open the valve. After running for about five minutes I close the intake valve, shut off the engine, and shut off the water. I then open all intake valves. Advice???
Thank you in advance, Bill

[furball]

Bill,
I found a good article on boatdiesel about this. I haven't done it but my understanding is this....
You don't want water pressure all the way to the water pump. Hose pressure is typically 60-80 psi. If you close the seawater intake and turn on the hose, you pressurize the system to the water pump impeller. The impeller may let water past, and with the engine not running, water ends up in bad places. The solution suggested placing the fresh water connection in between the seawater intake and the strainer. Leave the sea-cock open so any positive pressure will simply flow out the intake. No positive pressure can build in the system. I think some strainers have caps available that allow you to back flush the strainer at the same time. There was some concern about the ability of the hose to produce enough volume but at idle it should not be a problem for most systems. Easy to test, put the hose in the strainer and see if it keeps up.
Good luck.
John

[Carl]

I can tell you this, I have put the hose in the strainer while on the hard to run the engine for a few minutes before changing the oil. The strainer does not "overflow" with the hose on wide open. The water does come out at what looks to be a normal amount from both the exaust and the shaft seal. Also while winterizing with the pink stuff, you cant pour the gallon jugs in fast enough to make the strainer overflow. That pump moves some water!

[Drew]

We just sold a Shamrock and looking to buy a 28. We always flushed the engine after each use and only replaced the manifolds and risers after 8 years. My question...is the fresh water flush part of the standard equipment for the Albin? From what I have seen so far it appears it is not. If that is the case, any thought as to why not? And also, what seems to be the standard replacement time for manifolds and risers with salt water usage?

[Russell]

The manifolds and risers on gasoline inboard engines are made of iron which rusts in salt water. A fresh water flush delays their failure. Diesel engines use bronze heat exchangers and stainless elbows but some may use an exhaust elbow made out of iron. Every few years it is a good idea to treat with Rydlyme to remove the deposits in the heat exchanger but I see no reason to flush with fresh water after every use.

[JeffM]

Having a freshwater flush setup is a good idea. While the saltwater side of the engine is designed to handle seawater, eventually it will affect things. Better to have engine sitting with fresh water in it.

Need to have a properly set up freshwater flush and use it correctly. Where people get in to trouble when flushing an inboard is to have water flowing into the seawater side of the engine while the engine is not running. What happens is the water will flow past the seawater pump and can enter the engine through the exhaust valves. Water will fill up the engine before it exits the exhaust system because the exhaust elbow is normally at a higher elevation than the exhaust valves. In order to prevent this, never have water flowing into seawater side of engine under pressure without the engine running.

My freshwater flush is plumbed directly into the cap on the seawater strainer for both the main and the genset. The setup is such that a fitting is screwed into the seawater cap to which a ball valeve is attached. On the other side of the ball valve is the the fitting for the hose. I attach the hose to the freshwater flush and leave the flush ball valve closed and turn on the water. The seawater thruhull is open and I start the engine. After the engine is idling, I open the freshwater flush ball valve and close the seawater thruhull. I let is run for 5 plus minutes and then I turn off the water and after the water is off, I turn off the engine.

There is a brief period of time (from when you turn off the water and then the engine) when there engine is running with no seawater flow. The mechnaic I use told me this was ok and would not damage the impller. But this situation just did not feel right to me so I installed a ball valve in the middle of the garden hose I use and stand at the ignition when I turn off the water. I then immediately turn off the engine.

Even if you have a good freshwater flush system which you use, it is still important to maintain the seawater side of the engine. Every few years you should service the heat exchanger, after cooler and transmission cooler. Take them apart, clean the inserts and pressure test them. This will save money and reduce probelms in the long run.

Good luck

[jumpjet231]

http://www.pyacht.com/groco-engine-flush-kit.htm

I am thinking about installing the above kit. Does anyone have any experience with it?

[twomey]

I installed the groco engine flush two years ago. It works great for fresh water flushing and I also like the ability to use it as an emergency bilge pump. Because of the way my boat was plumbed, I had to install the flush adapter after the strainer, so I just close the seacock and make sure the strainer is full. Then I run a short length of hose from the flush adapter to a 5 gallon bucket. I fill the bucket as needed using a hose with a flow control valve on the end. This avoids any problems with too much water pressure, and also provides a visual indication of how much water is being pumped. That short length of hose stays in the bilge by the adapter so that in any emergency flooding situation, you can quickly drop that into the bilge and use the engine raw water pump as a bilge pump.

Tim

[sail149]

Re :exhaust manifold life.
Some time ago I was doing some wok with Osco mfg who make/made replacement manifolds for gas engines. I asked why none for diesel engines. They said the corrosive gasses , temperaturers and by products of a gas engine destroy the manifolds over time but the diesels do not .
Both manifolds would typically be made of cast iron by the way.
warren

[Russell]

I am not sure that guy knows what he is talking about. If the exhaust gases were the problem the exhaust manifolds would have a short life in cars too. The problem is the blistering hot salt water circulating around the exhaust manifold that eats it up. You must replace them every few years but then you find the bolts rusted into the block where they shear off causing even more problems. The Crusader brand of gas engines circulate the antifreeze engine coolant around the exhaust manifold but they still use seawater on the risers. Diesel engines that I am familiar with do not circulate salt water around the exhaust manifold.

[JeffM]

The reason to install a freshwater flush is not necessarily to protect the exhaust manifold. Most inboard diesel engines do not curculate seawater through the exhaust manifold. To the extent the exhaust manifold is cooled, it is done with the engine coolant. I know this is how a Cummins b and c are set up and most other modern diesels. Seawater is only mixed with exhaust in the exhaust elbow.

The main reason to have a freshwater flush is to protect the heat exchanger, aftercooler and transmission cooler and other parts of the engine. The salts in seawater can act as an electrolyte allowing for electricity transfer. Fresh water does not have the ions that can act as a conducter. Through seawater, your engine is connected electrically to all other metals on your boat that are in contact with the saltwater and possibly other boats on your dock through the shorepower ground. It may also be connected by the bonding system on your boat (if it isn't, I believe it should be). Seawater in the saltwater side of the engine can facilitate galvanic corrosion in various parts of the engine, especially if an issue arises with the zincs or bonding system. Fresh water does not act as an electrolyte like seawater meaning less corrosion issues are possible. Seawater often has little critters living in it and can result in gunk forming in the seawater elements. I recently had to remove a tube worm from the strainer. Things like the seals in the seawater pump will also last longer if not constantly exposed to saltwater.

If you have a cast iron exhaust elbow, it eventually may go due to the corrosive effect of the hot seawater. A freshwater flush is not necessarily going to eliminate this. When it does go, just replace it with a stainless elbow. This is what I did with my 450c.

Fresh water flush is a nice way to show a little love for your engine and possibly your wallet.

Jeff

[jruesr]

I am hearing a lot of talk about stainless steel exhaust risers. My Cummins 370 was installed with a stainless steel exhaust riser. I have seen several different designs of risers and mine may be unique. I have a salt water jacket that is continuous from the attachment point at the turbo to the exhaust hose connection with water injection into the exhaust at that point.

Salt water enters the jacket right at the turbo outlet. Some other designs only inject salt water near the exit point to the exhaust hose, and are thermally insulated at the point where it connects to the turbo.

My stainless riser burned a hole between the salt water jacket and the exhaust passage. This caused a huge series of problems. I took the riser to DeAngelo in Ft Lauderdale Florida. They make exhaust systems that will not fit through my front door. I mean thousands of horsepower units. According to them, my system failed because the portion of the pipe where the hot exhaust is on one side of the exhaust pipe and the salt water is on the other side of the pipe cannot be stainless steel. It must be inconel. On my systems design this point is right at the turbo. My new exhaust riser is completely inconel. This cost several hundred dollars more but compared to the problems that I have had this was a small price to pay.

We also added a drain fitting in the new riser so I can drain the water from the riser. I do not have a fresh water flush but will be adding something soon. I like the five gallon bucket plumbed into the strainer idea the best.

See photo of failed riser attached. It looks like someone patched the riser before I owned the boat (see weld patch) so this was likely a repeat failure and a cheep repair. Buyer beware.

John
1990 Albin 32
Passages III

[sail149]

For what it's worth I stand by my orriginal comment. Gas engines in Boats do eventually destroy their exhaust manifolds, Diesel engines do not. As ,I think Russell, pointed out the higher temperature gas engine exhausts are cooled by raw water, Diesel are not. A fresh water flush sounds like a good idea but I suspect most of the corrosion ocours when the engine is running, the high temperatures will speed up the chemical reaction or corrosion. Oscoc Motors http://www.oscomotors.com/ is in the business of making replacement gas engine exhaust manifolds because they do wear out. They did not make Diesel manifolds as there was no demand.
sail149/warren

[Dave]

The only time I use a fresh water flush is when I am getting the engine ready in the spring and the boat is on shore. I disconnect the seawater intake hose from the outlet side of the strainer, attach a 1" hose to it and put the hose in a 45 gallon drum of fresh water, start the engine and that little pump drains the drum in 4 to 5 minutes. I use the same method to winterize the system with about 6 gallons of the pink enviromental anti freeze.