Rinker 330 (Merc 5.7 EFI , Fresh Water Cooled) - How to Flush Cooling System

pistole

Hi. Am new here and just got a Rinker 330 powered by twin Merc 5.7 EFI engines driving Bravo3 outdrives. The engines are fresh water cooled.

I did a search and could not find anything (although I wouldn't put it past me to have missed some of the threads here) , apologies if this has been discussed before.

I was told by the former owner that the engines could be flushed with fresh water with a hose after use and pointed out a hose (or a pair of hoses) beside each engine which (as far as I can see) leads to a valve.

1. Is there any literature out there about how this flushing is to be done ? If none , is there some information here ?

2. I understand that the flush would push out the raw sea water from the heat exchanger and the manifolds/risers and was worried that I may inadvertently fill up the Y exhaust pipes with fresh water and then drown my engine. Is this possible if the flush is done without a running the engine ?

3. From the diagram of the Bravo3 outdrive , there isn't a water pump in there ? Would that mean that the raw sea water cooling of the engines relies entirely on the raw-water pump driven by belt at the engines which feeds from a thru-hole in the hull ?

Thanks in advance.

zaverin1

Raw water pump is engine driven but water still gets sucked in thru the drive 

Handymans342

The pump sucks the raw water thru the drives to cool them and thru the thru hull to cool the engines. I have the same setup so I hook a garden hose to the valve, close the thru hull for the engines and flush that way

reneechris14

Yes it is possible to flood engine if not running. When water mixes exhaust as it exits the riser the distances is not far enough apart. The air folw from the exhaust pushes the water out.
 A 1/2 inch hose can only carry 3.5 gals per min,from what I've read the pump pumps 7 gals per min at idle, so I feel that you could starve the pump.this is just my opinion.

randy56

To add to zaverin1 the water pump is not in the outdrive, it is attached to the engine block, 

jme097

He is referring to FWC not raw water cooled. I am assuming he has the shell and tube heater exchangers that he is wanting to flush

zaverin1

Don’t confuse raw pump with engine circulating pump.

jme097

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pistole

Handymans342 said:

The pump sucks the raw water thru the drives to cool them and thru the thru hull to cool the engines. I have the same setup so I hook a garden hose to the valve, close the thru hull for the engines and flush that way

Thanks. If the raw water thru Hull valve is closed and a garden hose is at attached for flushing wouldn't the raw sea water pump also draw seawater from the outdrive during the flushing? 

Handymans342

If the boat is in the water, yes

randy56

Zav, You are correct I can see how he may  get confused. Here's a diagram,
There is a sea water pump, as well as water circulating pump.
One more thought: Don't forget to flush!

https://www.perfprotech.com/blog/wp-content/uploads/2014/02/fwc-flow-diagram-copy.jpg

rasbury

I thought similar discussion was here before on two different fresh water cooled system, one being 100% and one being only 50%. I know I had a lot of issues with my water pump when I first got my boat. I had understood that some boats like mine were a 1/2 FWC system in that I have a heat exchanger/circulating pump similar to a car system and then a raw water pump that cools the heat exchanger as well as the heads and the risers. Also, I understood, some boats have the pick up thru the foot only and others have a thru hull as well- one thing for sure if your out of the water and your running on muffs and the thru hull is not turned completely off, you will toast the raw water pump....