I have twin 2017 250 Yamahas, and hate climbing all over to attach/detach the hoses to flush them after running. My question is whether anyone has ever simply run a couple hoses to the onboard fresh water system? Maybe plug the hole where the outboard flush hose attaches, and permanently keep the flush hose on there? From what I understand, the flush hose run is not a closed or important system for cooling, so it should be fine, no? Any thoughts are appreciated, as I haven't researched the outboard interior....
Marlin outboard flushing question
- Thread starter baldraver
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I keep a Flexilla flush system always connected with the hoses lying in the transom well. I have a 2nd "Y" adapter attached with a longer (?5') Flexilla hose for the 3rd engine on my 360 Express. When I run.. I keep all the splitter valves off and the engines run normally and water comes out of the "pee hole" normally. When I'm done, I hook up one hose to the system and open one port at a time. Still have to wait to flush each engine individually as it is all manual, but it eliminates leaning over the back or crawling around one tilted engine trying to unscrew the flush hoses, etc... and breaking my back. I'll send a pic next time I am on the boat. The Flexilla hoses aren't pretty sitting in the transom well (all the other control tubes are black), but it sure saves a backache leaning over to connect when the boat is in the water. https://www.flexzilla.com/water/marine-flush-kit/
Ekea
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this was done on a 330, but should be a good starting point for you
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Poor Man's Reverso
Getting close to wrapping up my Semi-Auto Engine flush on my 330. - I tee'd into the feed line for the Transom shower. it's a 1/2" vinyl reinforced hose. - Ran that under deck to transom area in generator compartment (There is no generator there at the moment) I tee'd it again to [2] 12v...
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Hookup1
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So you keep the flush system on there the whole time? Just laying on the transom? Do you have a pic?
Yes like Hookup1 said the male connection side is a dead end… certainly is on my ‘06 F250 model. You can feel it goes nowhere with your finger. Here is how it looks. I just hooked it up last weekend. Also put a salt-away mixer on it that I use sometimes. (When I do, I refill for each engine). Going to add some zip ties. Also have to be careful the screw ends on the Zilla hose don’t jam into a steering rod when tilting. 
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I find that the Melnor quick connects last two, maybe three seasons before the internal metal springs corrodes. They are cheap enough though to buy extras as spares.
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I would avoid using the fresh water off boat tank as you most likely use some chemicals to keep it "fresh". I also did see in some literature not to do that.
I am lucky to always have boat in wash rack after each run so no issue standing behind boat and connecting the hose. I also have the onboard quick flush but I feel it does not give enough of a water flow through it. Also you have to move attachment from motor to motor in cockpit.
I did get a 3 engine flush kit with Y connections and valves for each leg but it turned out the simplest is to just use the hose connection on each motor.
It is a dead end hose at the attachment so all above systems work and do not disturb normal cooling as long as the valves are shut when running.
U can make your own with garden hose couplings and valves, no high pressures involved or desired I believe. On my 2011 F300's I did have a reading for water pressure as I recall, have not seen that on the current 2019 ones.
I am lucky to always have boat in wash rack after each run so no issue standing behind boat and connecting the hose. I also have the onboard quick flush but I feel it does not give enough of a water flow through it. Also you have to move attachment from motor to motor in cockpit.
I did get a 3 engine flush kit with Y connections and valves for each leg but it turned out the simplest is to just use the hose connection on each motor.
It is a dead end hose at the attachment so all above systems work and do not disturb normal cooling as long as the valves are shut when running.
U can make your own with garden hose couplings and valves, no high pressures involved or desired I believe. On my 2011 F300's I did have a reading for water pressure as I recall, have not seen that on the current 2019 ones.