Plumbing to flush the raw water system safely

[haydude]

Several times I thought that I would like to flush the raw water cooling (Volvo Penta with heat exchanger) more often than once a year. Ideally every time, to save having one day to replace the very expensive heat exchanger.

Ideally I could fit a Y seacock just before the raw water filter. Turned one end the system gets water from the saildrive seacock, the other end instead is fitted to either

a) a free end hose which I can plunge inside a bucket that I fill slowly with fresh water whilst running the engine
or
b) an hose with a garden hose attachment that I can plug directly to the fresh water hose.

However my concerns are:

1) if the Y seacock can let in even the smallest amount of air when turned to the position that takes water from the sea inlet (normal running position), the effectiveness of the cooling system will be severly impaired
2) in case of (b) if the water flow coming from the tap is greater than what the engine raw water pump can take, the exhaust will fill with water which will flood eventually a cylinder damaging the engine.

Has anyone ever done this and how?

 

[prv]

Not quite the same, but I set up my plumbing with a rodding opening above the seacock. It's normally closed with a blanking plug, but that can be replaced with either the rodding fitting (a clear tube up to above water level, containing a plastic rod long enough to poke out the seacock) or a hosetail and a length of clear tube for flushing.

With the flushing tube fitted, I can put the end in a big bucket of water on the cabin sole and it will happily suck water out of the bucket; the amount coming out of the exhaust looks the same as usual.

I don't think a pressure supply is a good idea, for the reasons you suggest.

I wouldn't expect a modern ball valve to leak.

Pete

 

[haydude]

One more question, would a descaler mixed with fresh water or an acid based solution damage any part like the impeller?

 

[VicS]

However my concerns are:

1) if the Y seacock can let in even the smallest amount of air when turned to the position that takes water from the sea inlet (normal running position), the effectiveness of the cooling system will be severly impaired
2) in case of (b) if the water flow coming from the tap is greater than what the engine raw water pump can take, the exhaust will fill with water which will flood eventually a cylinder damaging the engine.

Rather than a Y valve why not put a Tee piece between the water inlet valve on the saildrive and the pump.
connect a ball valve to the branch, with a hose tail to which a hose from a bucket can be connected. The hose or hose tail can be plugged when not in use if you wish.

It is unwise to take pressure from the water supply directly to the cooling system because as you say the pressure, esp if you did not turn it off as soon a s the engine was stopped, could flood the exhaust system.

 

[GrahamHR]

VP themselves fit a flushing port to their petrol engines from around 2003. It's a Y piece in the raw water pump inlet hose and has something like a 1/2" dia hose attached to it. The other end is fitted with a screw fitting (and blanking cap) to which a garden hose can be attached. I changed that part on mine to a stainless ball valve and a brass quick fit coupling (it's which is normally capped with a blanking cap). According to the manual it's not meant to be used above idle speed; it also back flushes the outdrive once the engine is stopped ( very little water gets past the impeller when it's not turning, it's easier for the fresh water to go back to the outdrive than to the exhaust manifolds and risers).

I find the anode in the heat exchanger on mine lasts about a season ( about half eroded each year)

Graham

 

[vyv_cox]

One more question, would a descaler mixed with fresh water or an acid based solution damage any part like the impeller?

No non-metallic components that I can think of would be damaged by hydrochloric acid at the concentrations and time of exposure that are likely. Worst affected by a long way would be a zinc anode. Iron (the engine), copper (pipework) and brass (pump, thermostat, etc) are virtually immune to attack by dilute HCl. You cannot buy concentrated HCl other than from chemicals suppliers.

 

[rogerthebodger]

When we was fitting out my current boat and when we wanted to run the engine before launch we used method b) and all was OK until my mechanic stopped the engine and forgot to turn the tap feeding the hose off which then filled the cylinders with water. We found out when we tried to restart the engine.

Fortunately the engine would not even turn over so no damage was done.

 

[haydude]

VP themselves fit a flushing port to their petrol engines from around 2003.[...]I find the anode in the heat exchanger on mine lasts about a season ( about half eroded each year)
Graham

1) Who has a petrol engine?
2) is there an anode in the VP heat exchangers (diesel)? Where?

 

[GrahamHR]

I have a petrol engine !!!! As they firted an anode to the heat exchanger of their petrol engines, I imagine there would be an anode in the heat exchanger of VP diesel engines as well. on mine, it's screwed into a brass or bronze hexagonal headed plug, something like 11/16" across the flats. I've seen photos of some VP anode holders that had a square section, rather than the hex.

Graham