Volvo Penta D4 (& D6) Fresh water flushing

[trialframe]

I recently sold my single D6 powered boat & will shortly be getting another powered by twin D4's.
The main weakness of these engines (in my opinion) is the tendancy of the salt water cooling circuit to
build up internal salt deposits over time. Eventually these work their way out through the O rings & can lead to salt water dripping on the starter motor etc.
Has anyone fitted a system that would allow a fresh water flush just before shutdown (or an injection of 'Salt Away' etc) - that could prevent the problem occurring?

 

[GrahamHR]

I recently sold my single D6 powered boat & will shortly be getting another powered by twin D4's.
The main weakness of these engines (in my opinion) is the tendancy of the salt water cooling circuit to
build up internal salt deposits over time. Eventually these work their way out through the O rings & can lead to salt water dripping on the starter motor etc.
Has anyone fitted a system that would allow a fresh water flush just before shutdown (or an injection of 'Salt Away' etc) - that could prevent the problem occurring?

I was thinking about this as well; the Volvo Penta V8 petrol engine in my previous boat had as standard a flushing set up; basically a T piece in the water inlet before the raw water pump. There's no reason why such a set up wouldn't work on the D4 ( and why it's not standard, heaven knows !). I'd have fitted one already but I just don't know the inlet hose size.

 

[trialframe]

Yes since I haven't got my new boat yet,obviously need to know inlet hose size. Would be nice to hear from someone who's got this up & running though - even on a different type of engine.

 

[volvopaul]

Yes, I have fitted a system for an owner before plumbed from the boats own on board system.

 

[Sdpaddler50]

A friend with dual 8.1 Merc, Gas, fitted his own system for this. He spent about $100 to tie in a connection to flush the manifolds. If you google it, you can find others, and perhaps more details and some schematics. You need to be careful its a robust system, wont break, and you open/close the valves in the right order, or you can create some big problems.

I also had the 8.1 Gas on our previous boat, and was going to do the flush, but we sold the boat. We now have the D6, and the local vendor here said he can do it, but not something he has done before, and i was not sure it was something i wanted to mess with every time. if you end up implementing, please post some pictures and a schematic.

 

[trialframe]

Any chance you could post some details of the system you fitted? Thanks

 

[volvopaul]

Every install depends on engine make and intake set up as to what valves are required.

 

[GrahamHR]

Every install depends on engine make and intake set up as to what valves are required.

Isn't the raw water inlet hose to the pump on the D4/6 a standardized size in terms of ID ?

On the later VP petrol V6/V8 engines, the flush set up is very simple; a simple T piece in the water inlet hose. As standard, it terminates in a US garden hose coupling/ cap. I put in a stainless ball valve and a Gardena type quick release coupling and cap. Once the engine is switched off, it backflushes to the outdrive. So simple and incredibly cheap for the OEM, I guess the Swedish VP guys has the "not invented here" syndrome and wouldn't accept what their USA VP colleagues had done !

 

[Anders_P42]

I have single D6-370. Doesn't fresh water flush pose more of a risk of freezing in winter?

Does the above leaking issue effect newer engines or only older models?

 

[GrahamHR]

I have single D6-370. Doesn't fresh water flush pose more of a risk of freezing in winter?

Yes, if you leave fresh water in there. The same flush inlet though can be used to introduce an antifreeze/ water mix. That's what I used to do with the V8; a bucket with a hose out of the bottom, above the top of the engine; it was easier for the engine water pump to suck that mix in from the bucket than it was via the outdrive inlet/ muffs, which was much lower down.

 

[GrahamHR]

As a matter of interest, I looked at the parts schematic for the raw water system. There seeks to be a "T -piece" in the water inlet hose already (at the opposite end of the hose that connects to the water pump; part # 3584430). The drawings don't show what the side connection connects to, if anything as standard; it looks a to be small diameter though in the drawing.

 

[Anders_P42]

Yes, if you leave fresh water in there. The same flush inlet though can be used to introduce an antifreeze/ water mix. That's what I used to do with the V8; a bucket with a hose out of the bottom, above the top of the engine; it was easier for the engine water pump to suck that mix in from the bucket than it was via the outdrive inlet/ muffs, which was much lower down.

How many litres does that take / cost every time? Must be 5 or 10 litres, or am I missing something? Sounds expensive if you use boat a lot, would it be better to have raw water side flushed every two years with that special stuff, I forget the name of it...begins with 'R' I think?

 

[sap_2000]

I installed a simple system to flush my Cummins QSB 5.9 raw water circuit.
My raw water strainer is a Groco with a very solid lid with external threads, so I ordered a 2nd lid and installed a trough-hull fitting with o-rings, a 1" ball valve and a hose fitting.
I would not recommend this method on a thin and flimsy lid. Then I would plumb up something and connect it to the intake hose before the strainer instead.

This system requires me to open the hatch, close the intake valve and open the valve above the strainer. Then run the engine for a few minutes. I have made up a piece of garden hose with a Gardena valve so I can start and stop the engine and water supply simultaneously.
Initially I had a 3/4" hose with a Gardena coupling that connected directly to the garden hose on the dock, but the engine required more water that the hose could supply even we have pretty good pressure, so I went back to a short piece of 1" hose that I just put the garden hose into.

For winter storage I just replace the short 1" hose with a longer one that runs up to a 25 liter drum of anti freeze mix on the salon floor. No pouring and no spills.
Difficult to post pics on this forum from iPad, but I made a short video clip.

Having seen what corrosion and salt deposits can do to the sea water circut over time, I am happy with my simple system.
It gives me piece of mind knowing that everything from the raw water pump, fuel cooler, intercooler, gear cooler, heat exchanger, exhaust elbow is flushed and rests with fresh water 95% of the time the boat is on the water. It takes me 5 minute after the boat is tied up and I have made it a habit to to it after every trip unless I am going out the next day or two.
For the other half of the year I run anti freeze through the system. The winter is too long and too cold here :-(

http://youtu.be/YdqVulR5STo

Stern drive engines don't normally have intake valve, but on a D4/6 one could make a T-manifold with a valve and install it on the raw water hose that runs from the transom along the side of the engine.

 

[GrahamHR]

How many litres does that take / cost every time? Must be 5 or 10 litres, or am I missing something? Sounds expensive if you use boat a lot, would it be better to have raw water side flushed every two years with that special stuff, I forget the name of it...begins with 'R' I think?

My V8 had "closed cooling" for the block and heads, with a heat exchanger and the fresh water flushing was only affecting the exhaust manifolds, risers and heat exchanger (and the power steering cooler, once the engine was stopped. ) When the boat was on the water ( April to end September usually) the fresh water that remained in there didn't freeze, even in Anglesey ! The antifreeze mix was only used when the engine was "winterized" so a one off yearly event, as the block and heads were not flushed, the quantity required was less than 5 litres.

 

[trialframe]

Thanks for all your replies. Does anyone know where I can source a 38mm T piece?

 

[Anders_P42]

My V8 had "closed cooling" for the block and heads, with a heat exchanger and the fresh water flushing was only affecting the exhaust manifolds, risers and heat exchanger (and the power steering cooler, once the engine was stopped. ) When the boat was on the water ( April to end September usually) the fresh water that remained in there didn't freeze, even in Anglesey ! The antifreeze mix was only used when the engine was "winterized" so a one off yearly event, as the block and heads were not flushed, the quantity required was less than 5 litres.

I see, so it's not flushed every time after use. I don't think that will help much with the salt deposit issue in the charge cooler.

 

[GrahamHR]

I see, so it's not flushed every time after use. I don't think that will help much with the salt deposit issue in the charge cooler.

??????????? It was flushed (religiously) after every use when it was afloat with fresh water for about 10 minutes or so. After 8 years I took off the heat exchanger end caps; there was NO build up in there or the tubes I could see; maybe microscopic, but I didn't see the need to try to measure it). It's astounding that a cheap to implement fresh water flush set up is not standard on all marine engines, regardless of whether they are petrol or diesel, raw water or closed system cooled.

 

[GrahamHR]

Thanks for all your replies. Does anyone know where I can source a 38mm T piece?

So you know 38mm (1-1/2")is the ID of the hose to the D4/ D6 water pump ? Even if no suitable T piece part exists as yet, there may (should ) be enough potential customers to make it worthwhile some company making one !

 

[trialframe]

Further thoughts

I haven't got my boat yet - expecting it very soon, but I think D4 uses 38mm id hose (think D6 may be 50mm?)
If you Google Adit marine (Australian), they do a kit with motorised valves which looks good. However this doesn't shut the inlet seacock, it just injects fresh water at hose pressure upstream of the inlet. Trying to figure out if this would be effective enough?

 

[beejay190]

One of the many advantages of keeping my boat in a Drystack . I flush the raw water side of my D4 either immediately after use or within 48 hours of lift out.