Another flush question ( Part 2 )

mnm99

Well-Known Member
Oct 2, 2015
2,445
Long Island
Boat Info
2004 340 SeaRay Sundancer
Engines
Twin 8.1 Merc
I thought I'd start another thread with my results and new setup I'm going to install. So was trying to figure out how to flush my engine without lifting the hatch and close the Seacock every time. My friend told me about a Hydrometer. The hydrometer measures the salt content in the water. Salt content near me is around 32-34. SO...What I ended up doing is install a Tee inline after the Seacock and before the strainer. The top part of the TEE is connected to a fresh water hose. With the water off I ran the motor for 5 minutes. I then tested the water leaving the side exhaust water outlet. Picture #1 shows the results. While the engine was running all I did was turn on the fresh water. Water pressure on the engine stayed the same. I then ran it for the same 5 minutes and picture 2 shows the results. I was amazed at what I found. The content read 0..!!!. I even tasted the water with my tongue and there were no traces of salt. That was good enough for me..This winter I'm going to install 2 Bronze TEE's with enough re-enforced hose to reach the locker. In the locker I'm going to install a valve with a cap so I can flush every time I come in. Let me note also. I pulled the hose feeding the transmission cooler. This hose is the first one after the pump that feeds the engine. I then turned the water on with the engine OFF and no water was coming out. This tell me I have nothing to worry about if I leave the hose on when the engine is off...
I am going to disconnect my Saltaway system also. When I pulled the TEE off ( shown in pic 2) I found a decent amount of goopy buildup near the injection point. I'm wondering if this is in my coolers also. Remember, I could also use my Saltaway mixer connected to the hose if I want.
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I tried to get an answer from Mercruiser Tech, but no luck. Maybe you can give me your thoughts. I have the built in flush connections on the top of my 350 MAG MPI engines. I'm also trying to avoid opening the hatch and closing the seacocks everytime I want to run Salt a Way through. Do you think I can hook up the Saltaway mixer/hose to the flush connections and run it through with the seacocks open as well? This would result in two water sources feeding the seawater pump (fresh and seawater). Is this potentially damaging or will the engine just pull whatever it needs in terms of flow from the pump, whether raw water or fresh water from the flush connection? Also, based on your experiments, do believe that the saltaway would work sufficiently with sea water in this scenario? Also wondering if the pressure from the hose/flush connection would override the seawater pressure resulting in a mostly fresh water flush?

Thanks!
 
Yes that's what I found. The fresh water overoad the salt water. I proved it with the hydrometer test. Not sure how your flush works. Using salt away may help too.
 
That's pretty interesting. Would have never guessed it.

The rubber impeller makes a pretty good seal and I guess the hose water took the past of least resistance and exited under the boat. I'd still be very cautious with running 40+ psi water towards the engine! Avoid at all costs!
 
That's pretty interesting. Would have never guessed it.

The rubber impeller makes a pretty good seal and I guess the hose water took the past of least resistance and exited under the boat. I'd still be very cautious with running 40+ psi water towards the engine! Avoid at all costs!

I would have never guessed it either. I'm going to go to the extent to have it tested local to see how much salt content they come up with. They have testers live pool chemicals and microscopes...LOL
When I turned the water on with the engine OFF I noticed water come out from the pickup at the bottom of the boat. I can't imagine any PSI at the impeller since the water hose inlet is only a foot away from the bottom of the boat.
 

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