Mercruiser 5.0 1(a) - MPFI Single Point Drain Cooling System (Complicated)

In this video I describe how water flows through a single point drain system on a Mercruiser 5.0 MPFI marine engine. It’s so complicated that I had to document the system before disassembly or I would struggle putting it back together. Hopefully this helps those who may have gotten a boat in pieces to put it back together.

[mikedodd]

great video, I learned a lot. Looks just like my 350 MAG MPi.

[BellavistaPEI]

Very informative video! Thanks for taking the time and posting it!!!

[TaylorTaylor-yiqd]

Thank you for explaining the cooling system. I having a hell of a time tracking down a coolant issue. At idle it runs around 170 get on plane jumps up to around 200. Risers are cold to the touch but the thermostat housing is hot to the touch. New long block with new thermostat and circulation pump (one that car guys call a water pump)

[danielbodurian]

Good video. Just don't trust that single point drain for winterization though. In addition, You have to open the blue drain plugs (between 5-7 of them) and stick a tie rap into the holes to un-crust the rust so that the water will flow freely. Then you need to get MARINE antifreeze (not the pink stuff) into the block. Now some guys use the muffs to do this others disconnect the hoses on the front of the engine thermostat and pour it in there. Its up to you. Also, there is alot of debate as to whether leave the antifreeze in or drain it. Again, do your research. I prefer to leave it in because it has corrosion inhibitors built in that will help prevent issues over the cold winter months. Also, if you live in Florida or have an outboard consider yourself very lucky because you can ignore all this!

[juhavehnia]

Great video! Some of this stuff is really hard to see while the engine is installed.

[juvehill]

also does water go through manifold through top riser hose as well? and leave the manifold drain? if not then i dont see how the manifold can ever be flushed with fresh water through muffs ect..

[juvehill]

question.. if i connect a garden hose right to the fitting a bottom of exhaust manifold, how much water should come out elbows or risers, im trying to check flow through manifolds but when i connect to bottom of each there is just back pressure (if drain is plugged ect. )

[carmencordero]

Another great video can i convert my single point system to a regular kind to simplify the system to many hoses for little gain.

[cecilhillier]

Great Video, thank you for doing this, at 4:32 you show the Y fitting that feeds the main engine water pump, is the other part of the Y fitting also filled with water feeding the thermostat housing (thermostat closed) does this water entering the thermostat housing flow out to cool the exhaust manifolds. Am I understanding correctly that when the engine is running, the engine water pump is always flowing through those two holes and returning through the block drains, then when the thermostat opens we get water flowing through the block and engine head returning through the thermostat housing and back through the Y fitting to mix with other raw water to feed the engine pump again.

[billybolt]

how do you remove the fuel cooler on these engines? Thank You for the videos

[donschlegel]

Thank you very much for explaining that I appreciate it I have the same engine and my water distribution housing is leaking is that not that’s not normal right appreciate any help thank you

[Kiikonic]

Hello, how are you, thank you for video extremely helpful.
But I need a help, instead of a handle I have a long rubber tiny tube/pipe attached on the top of water distributor housing, and I can not understand is that for draining? Because this tube was placed all the way up and thrown on top of my engine and on another engine it's just hanging down from distributor housing.
If you can please explain point of that rubber tube and how to properly place it😊 mercruiser 6.2 horizon
Thank you again

[raulfernandez]

Does the exhaust manifold check valve come apart? I can see in the parts diagram that you can buy an oring and a little ball that go inside. Does it just twist open?

[cavalrylogisticsllc]

hi the hose that's on bottom of raw water pump what its for. Thanks

[beaverml]

I got the same system on my boat I have a question about the way to fill the block and the manifolds. Right next to the thermometer off to the right is a bolt kinda of on a angle a bit could that be removed and filled with coolant and it would fill the block and manifold?

[hookedonboating]

Do the small hoses that run from the block to the drain manifold also have quick connects at the manifold like they do at the engine block connections?