OK – I am posting this in the hopes you may all take a look and find some flaw in my thinking, save me some grief if I put a lot of effort into it. So please don't hesitate to pick apart my idea and express what you may think are drawbacks.
This has to do with fresh water flushing of engines that are fresh water cooled with raw water heat exchange. I'm dumping thousands into replacing virtually every salt water element on both engines and so I really want to get the max life out of my new systems. That means fresh water flushing after every run (I'm in salt water).
Problem is I see some drawbacks to the traditional approach of fresh water flushing. Normally the approach is to install a T into the intake raw water line between the strainer and sea cock, or between the strainer and the raw water pump. Some guys just open the strainer and put a hose in there but that is effectively the same thing. Shut off the sea cock and run the engine on fresh water for half an hour. Agreed?
Here are some drawbacks to this flush:
1) You have to do the flush right after the cruise while the engine is warm. This is because if you wait a couple hours, days – whatever, you will be running a cold engine for half an hour and that is bad for many reasons. Bad for the oil, valves, rings and such. You should always bring your engine to full temperature with every start. Well – this may not be convenient! You come in from a dinner cruise and want to go home not spend an hour flushing. Or for whatever reason you just want to put it off.
2) The reason you have to run the engine at all is to drive the raw water pump – period. You aren't doing to circulate the fresh water per se, if you had an electric pump pushing the water it'd work just as well without the engine running. So you are adding a half hour of slow rpm time to each engine every time you flush simply to push water.
3) You have to access the engine room. That can be a pain in the butt, and with the various valves and moving the hose from one to the other you will be in and out of the engine room several times each flush. After a while of this you become more reluctant to flush and it gets skipped from time to time. (at least with lazy me…)
4) There is some argument that you may not be getting enough flow from a dock bib and garden hose to adequately cool the engine even at the lower (say 1500RPM) speed used for flushing. A typical bib and garden hose are rated at 500 gallons per hour full flow. I looked up the specs for my Sherwood raw water pump and at 1500 RPM it pushes around 750 gallons per hour. So it is arguable there may be hot spots in the engine that don't show on the temp gauge using a water hose.
Now – I ask – why do it this way? What if we install the T between the raw water pump and the oil cooler, at least in my configuration those are the two earliest points. A simple T and you bring a 5/8" hose back to the transom or wherever, attach to a good globe valve, a bit more hose to a Y fitting which has the other engine coming in the same way, and the final connection is through the transom to a threaded male that accepts the garden hose.
Now the advantages are many:
1) You don't have to run the engine at all! You are no longer dependant upon the raw water for circulation. You have 45 pounds of domestic pressure to force that water through your engine circulation system (one engine at a time for sure). It is true you will not be running fresh flush water through your raw water pump, but with brass, stainless and rubber construction I don't care. The only argument I can see here is that you are running cold water through a hot system. Not through the block though! So it may well be that there is no risk of shock or cracking and that is one argument I invite you to comment on.
2) You can flush whenever you want! Without having to run the engine you can do it a couple hours later, the next day or whenever because you don't have to start and run a cold engine. Since you don't have to drive that raw water pump you have eliminated the only reason for running an engine during flush.
3) No trips to the engine room! You open one valve at the transom to allow the fresh water to flow into the system under pressure. The rubber impeller is plenty stout enough to prevent the flow of water to go beyond the pump into the strainer, so you don't have to close the sea cock. Simple! And conversely, once done and you secure that globe valve it will hold against the delivery of salt water when normally underway. Of course I'd use good heavy salt exhaust hose throughout.
4) You don't even have to leave the boat attended. No way would I walk from my boat at the dock with the engines running during a flush. But with a hose pushing water and no moving parts – all systems down – I'm free to run up to shore and take care of other chores.
5) You don't risk overheating the engine during fresh water flush for obvious reasons.
I see this installation as simple but no doubt several hours of careful routing and quality workmanship to do it right. Still it is very simple. And the output nipple on my Sherwood pump is threaded so I can remove the straight pipe and install the new threaded T right there – very simple indeed.
I tell you boys it's genius – pure genius.
Isn't it???
This has to do with fresh water flushing of engines that are fresh water cooled with raw water heat exchange. I'm dumping thousands into replacing virtually every salt water element on both engines and so I really want to get the max life out of my new systems. That means fresh water flushing after every run (I'm in salt water).
Problem is I see some drawbacks to the traditional approach of fresh water flushing. Normally the approach is to install a T into the intake raw water line between the strainer and sea cock, or between the strainer and the raw water pump. Some guys just open the strainer and put a hose in there but that is effectively the same thing. Shut off the sea cock and run the engine on fresh water for half an hour. Agreed?
Here are some drawbacks to this flush:
1) You have to do the flush right after the cruise while the engine is warm. This is because if you wait a couple hours, days – whatever, you will be running a cold engine for half an hour and that is bad for many reasons. Bad for the oil, valves, rings and such. You should always bring your engine to full temperature with every start. Well – this may not be convenient! You come in from a dinner cruise and want to go home not spend an hour flushing. Or for whatever reason you just want to put it off.
2) The reason you have to run the engine at all is to drive the raw water pump – period. You aren't doing to circulate the fresh water per se, if you had an electric pump pushing the water it'd work just as well without the engine running. So you are adding a half hour of slow rpm time to each engine every time you flush simply to push water.
3) You have to access the engine room. That can be a pain in the butt, and with the various valves and moving the hose from one to the other you will be in and out of the engine room several times each flush. After a while of this you become more reluctant to flush and it gets skipped from time to time. (at least with lazy me…)
4) There is some argument that you may not be getting enough flow from a dock bib and garden hose to adequately cool the engine even at the lower (say 1500RPM) speed used for flushing. A typical bib and garden hose are rated at 500 gallons per hour full flow. I looked up the specs for my Sherwood raw water pump and at 1500 RPM it pushes around 750 gallons per hour. So it is arguable there may be hot spots in the engine that don't show on the temp gauge using a water hose.
Now – I ask – why do it this way? What if we install the T between the raw water pump and the oil cooler, at least in my configuration those are the two earliest points. A simple T and you bring a 5/8" hose back to the transom or wherever, attach to a good globe valve, a bit more hose to a Y fitting which has the other engine coming in the same way, and the final connection is through the transom to a threaded male that accepts the garden hose.
Now the advantages are many:
1) You don't have to run the engine at all! You are no longer dependant upon the raw water for circulation. You have 45 pounds of domestic pressure to force that water through your engine circulation system (one engine at a time for sure). It is true you will not be running fresh flush water through your raw water pump, but with brass, stainless and rubber construction I don't care. The only argument I can see here is that you are running cold water through a hot system. Not through the block though! So it may well be that there is no risk of shock or cracking and that is one argument I invite you to comment on.
2) You can flush whenever you want! Without having to run the engine you can do it a couple hours later, the next day or whenever because you don't have to start and run a cold engine. Since you don't have to drive that raw water pump you have eliminated the only reason for running an engine during flush.
3) No trips to the engine room! You open one valve at the transom to allow the fresh water to flow into the system under pressure. The rubber impeller is plenty stout enough to prevent the flow of water to go beyond the pump into the strainer, so you don't have to close the sea cock. Simple! And conversely, once done and you secure that globe valve it will hold against the delivery of salt water when normally underway. Of course I'd use good heavy salt exhaust hose throughout.
4) You don't even have to leave the boat attended. No way would I walk from my boat at the dock with the engines running during a flush. But with a hose pushing water and no moving parts – all systems down – I'm free to run up to shore and take care of other chores.
5) You don't risk overheating the engine during fresh water flush for obvious reasons.
I see this installation as simple but no doubt several hours of careful routing and quality workmanship to do it right. Still it is very simple. And the output nipple on my Sherwood pump is threaded so I can remove the straight pipe and install the new threaded T right there – very simple indeed.
I tell you boys it's genius – pure genius.
Isn't it???