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Engine Flush Systems
https://www.smwebhead.com/phpBB3/viewtopic.php?f=6&t=3151		 Page 1 of 1
Author:  kenxq5471 [ Sat Apr 04, 2009 10:13 am ]
Post subject:  Engine Flush Systems
I have a 03 268 Vista with a 6.2 mercruiser. I use this boat in saltwater so engine flush is vital after every use. I installed a neutra-salt system but I am not convinced it works properly, always pumping in the salt neutralizing solution. I am getting tired of climbing down the swim platform ladder to stretch and put muffs on the outdrive while my boat is hanging on the lift. Has anyone else installed an engine flush system and could you recommend a solution here. I would like to have a system that would let me just open the stern locker and hook up my garden hose to flush the engine instead of having to open the engine hatch or crawl down the ladder.

Thanks
Author:  wkearney99 [ Sat Apr 04, 2009 10:37 am ]
Post subject:  Re: Engine Flush Systems
From what I've read the plastic Perko flush unit is something to be avoided. The few that I've heard about have suffered engine overheating when the unit failed. The basic idea seems good, the unit has a spring and a valve in it that shuts off the incoming seawater when pressure comes in from the garden hose hookup. Making it a hands-off operation, other than the hose hookup, of course.

I read there's a Mercruiser flush system for their engines, but haven't heard much more than that.

I've also read about people putting a Tee in their incoming seawater line and then fitting a valve onto that, with a hose running out transom for a shore hookup. You have to manually open and close the valves. Shut off the seacock first, then open the valve to the hose and then run the engine at nothing more than an idle. Any higher RPMs and the suction of the engine impeller will pull so hard it'll collapse the hose.

Flushing the engine isn't always a trivial exercise as there are issues with how the water is routed with the thermostat.

While it's a hassle using the muffs you're at least SURE the water is coming in from the same place as always. In theory that means the fresh water is going to the same places as the seawater. But when that colder fresh water hits the thermostat it'll close, potentially leaving seawater in the engine. That's the real point of a thermostat, to only open when the engine gets warm enough to operate properly, not to "cool" then engine. The thermostat isn't smart enough to know that cooler water is intended for flushing. It closes and all your fresh water goes right overboard instead of continuing through the engine block.

I wouldn't mind having a flushing feature on my 6.0L Crusaders inboards. But the hassles of manual valves, or worries about an automatic one failing have left me a bit unsure about the idea. If it wasn't such a pain in the ass to get down into the engine compartment I guess the manual valves would be my preferred solution.
Author:  Graham R [ Sat Apr 04, 2009 10:44 am ]
Post subject:  Re: Engine Flush Systems
If you have a Bravo drive, you could consider fitting the engine flush system fited to later VP drives; it's basically a T piece that goes on the inlet side of the raw water pump. The parts diagram is on the Doug Russel web site.

The Neutrasalt solution is not actively injected in, it is sucked in by the raw water pump. Depending on the year of your Neutrasalt system, there could be a filter between the reservoir and the solenoid valve ( on mine it's a grey thing around 3" long). Things like to live in the Neutrasalt solution and at the end of last season mine stopped working and I found the reservoir ( plus filter) full of a black slimy stuff!. I recently changed my riser and manifold gaskets; there was remarkably little rust in the risers or manifolds after 4 seasons use in salt water, so the Neutrasalt certainly seems to do something

Graham
Author:  kenxq5471 [ Sat Apr 04, 2009 1:33 pm ]
Post subject:  Re: Engine Flush Systems
Thanks guys. My neutra-salt system was just installed when I bought the boat in 2007. The engine already had 350hrs but had been rack stored and flushed after every use. I thought the investment in the neutra-salt system was a good one. I found that the system was somewhat unrealiable. I made a mark on the reseviour and sometimes it seemed that the solution was making it to the engine and sometimes it wasn't. That is why I decided to not only use the neutra-salt, but also afterward I also would fresh water flush. I like the idea of being sure that the engine was being flushed out and not relying on just the neutra-salt system. I agree that the muffs are a bit failsafe but it is a chore reaching the outdrive, and it is a bravo III, to put the muffs on. It is everything I can do to avoid falling in the canal.
I wonder if there is a way to be able to install the bypass without having to get down in the bilge to operate the valves. The 268 bilge is a tight fit with the 6.2L, generator, water heater and macerator. Beautiful boat, just a small engine compartment for a big guy. Tried to sell it for the last year to get something bigger and with the boat market being what it is the highest offer I got was 32k and they didn't have good credit. A cash buyer was there at 29k but I am just not going to sell such a nice boat at a firesale price, even if I do want a bigger boat.
I will just continue to take excellent care which is what was leading me to searching for an alternative flushing approach.

Thanks Again
Author:  Graham R [ Sat Apr 04, 2009 5:09 pm ]
Post subject:  Re: Engine Flush Systems
The VP flush set up is very simple and has no valves to shut off. The hose is simply attached via a standard hose attachment ( I changed mine to a quick fit coupling) . Any excess water from the water hose that the engine is not calling for exits via the outdrive.

Graham
Author:  kenxq5471 [ Sat Apr 04, 2009 8:20 pm ]
Post subject:  Re: Engine Flush Systems
Graham,

Do you have the actual website for the Dave Russel website. I did a search and came up with everything but what I was looking for.

Thanks, ken
Author:  Graham R [ Sun Apr 05, 2009 3:29 am ]
Post subject:  Re: Engine Flush Systems
The Doug Russell website is:

http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=group&type=volvo&group=

I can't find the diagram on that site, I was sure it is on there somewhere! It is on this one though;

http://www.marinepartsexpress.com/VP_Schematics/GAS/5.OGXi-F_5.OGXi-FF_5.0OSi-F_5.0OSi-FF/COOLING%20SYSTEM/Seawater%20Pump%20and%20Hoses.pdf

Graham
Author:  wkearney99 [ Sun Apr 05, 2009 10:11 am ]
Post subject:  Re: Engine Flush Systems
There's two hoses coming into it: #17 and #19, with 19 presumably being the raw water intake. But if that's a plain Tee fitting (or a wye as per that picture) then how does it restrict seawater from coming into it from #19?
Author:  Graham R [ Sun Apr 05, 2009 2:53 pm ]
Post subject:  Re: Engine Flush Systems
Basically, it relies on the fresh water pressure from the hose being greater than the water pressure due to head of the salt water. So, the fresh water's higher pressure prevents salt water entering.

From memory, a head of 33' salt water results in 1 atm/ 14.7 psi pressure (above atmospheric pressure). So, the typical depth of water above the inlet hose of about 2' max would give rise to about 0.9psi, well below normal fresh water hose pressure. OK, once the flush is complete and if the boat is still in salt water, sodium chloride etc would diffuse into the fresh water, my physical chemistry lectures are far too many years ago for me to remember how to calculate the rate of concentration rise!

Graham
Author:  wkearney99 [ Sun Apr 05, 2009 3:47 pm ]
Post subject:  Re: Engine Flush Systems
Ah, thanks for the explanation. I can't say with certainty, but on the 348 there's not a lot of the engine cooling plumbing that's below the outside water line. At least not with a freshwater (antifreeze) setup. So it's not like there's going to be a lot of pressure exerted once the engine is shut off. The amount of salt water mixing would still probably end up being less than without any flush at all.
Author:  Beer-garita [ Sun Apr 05, 2009 11:27 pm ]
Post subject:  Re: Engine Flush Systems
Graham R wrote:
Basically, it relies on the fresh water pressure from the hose being greater than the water pressure due to head of the salt water. So, the fresh water's higher pressure prevents salt water entering.

From memory, a head of 33' salt water results in 1 atm/ 14.7 psi pressure (above atmospheric pressure). So, the typical depth of water above the inlet hose of about 2' max would give rise to about 0.9psi, well below normal fresh water hose pressure. OK, once the flush is complete and if the boat is still in salt water, sodium chloride etc would diffuse into the fresh water, my physical chemistry lectures are far too many years ago for me to remember how to calculate the rate of concentration rise!

Graham


Forget the old chem lectures. You just blew my mind with the water pressure stuff!! Your memory is fine!!!
Author:  Graham R [ Mon Apr 06, 2009 2:11 am ]
Post subject:  Re: Engine Flush Systems
Another thing to bear in mind; the static pressure in the fresh water hose is not the most important thing, it is the pressure that is maintained in the hose as flow is occuring. The faster the engine is running, the more raw water the pump is trying to pass through. Depending on the fresh water supply hose diameter/ length, if it is restrictive to flow you may come to a point where the effective pressure becomes below that of the salt water head pressure. In which case, salt water will also enter. For this reason, it's best just to flush at idle speed.

Graham
Author:  wkearney99 [ Sun Apr 12, 2009 12:48 pm ]
Post subject:  Re: Engine Flush Systems
Graham R wrote:
For this reason, it's best just to flush at idle speed.

Graham's absolutely right about this. I can recall seeing a buddy's sterndrive setup pulling enough vacuum that it sucked the hose flat if he throttle up even a few hundred RPM above idle. I'm sure others with trailer boats have seen the same thing when using the muffs.
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