5.7 Mercruiser flushing options

[pursuit2460]

Just got done replacing the exhaust manifolds, elbows and raw water pump. I currently have the Mercury flush kit that t’s into the main water pump hose. So I ran the engine and noticed that the starboard side manifold runs cool, 100* the port runs around 135-140*. By the way I have a closed cooling system. Anyways, decided to do an experiment to see if both manifold would run the same temp. I taped off the lower unit water pick up holes and removed the mercury flush kit and connected the water hose straight to it. Both manifold ran the same temp and also ran about 5* cooler(95*). So apparently the mercury kit doesn’t give enough water flow to keep both manifolds at an even temp and when throttled up it collapsed the hose. I have never had an issue with muffs but then again I have never owned an inboard. Should I run muffs or adapt some fittings to allow full water flow when flushing out the engine?

 

[alldodge]

A hose will almost never supply enough water to keep system "full", so one side will always run a bit hotter.

To use a flush kit the seacock must be closed so all water from hose goes to motor and nothing goes out strainer

 

[pursuit2460]

A hose will almost never supply enough water to keep system "full", so one side will always run a bit hotter.

To use a flush kit the seacock must be closed so all water from hose goes to motor and nothing goes out strainer

Mine has no sea ****. I have a Bravo3. The hose coming from the LU is where the T is spliced in for the flush kit. That’s why I was wondering if muffs would provide a better flow through out the system. Don’t ask me why but it just doesn’t sit well with me to have a 30-40* temp differential on the manifolds.

 

[alldodge]

With a B3 drive you have a I/O and not a

I have never owned an inboard.

Do run it off muffs and not the flush fitting.
If you do have dual water pickup (holes at nose of drive) tape or seal them up when using muffs

 

[pursuit2460]

With a B3 drive you have a I/O and not a


Do run it off muffs and not the flush fitting.
If you do have dual water pickup (holes at nose of drive) tape or seal them up when using muffs

Well as you can tell I haven’t got use to saying I/O. As always thanks for the help.

 

[QBhoy]

Manifolds and risers are consumable parts. No big deal. Even raw water cooled versions have managed to survive half a century by now…more damage is done to them by leaving them empty and not filled with a protective medium over storage or winter lay up. As some on here once told me ( might have been @Bondo ) there’s yet to be a known recorded case of one of these rotting right through by the hands of salt water corrosion, in terms of the block itself. That’s how Harry they are. But manifolds and risers are consumable and expect to have to change then out every now and then. Longer lasting if flushed and left filled with antifreeze over winter though.