What antifreeze for raw water?

[vyv_cox]

If the boat is out of the water, I thought it was the norm to just drain the raw water side down.
If it stays in the water, then do nothing unless it's in the Baltic!

Exactly so. Flush through with fresh water, I tip 5 litres into the strainer once ashore, then open the seawater pump, which drains everything. Heat exchangers will drain either forward or aft. If in a really cold place it is worth draining the trap: I used to do this ashore in the Netherlands. Then just leave everything dry, which it will be if the engine was warm before flushing. All the pipework on my Yanmar is rubber, so no problems there.

 

[Hallberg-Rassy]

I read a bit of discussion about whether anti-freeze protects from internal corrosion. Running it dry would make more sense to me but how to do so safely?

I got caught out once with humidity entering the intake causing the piston rings to rust & seize the engine. It was a common liability on old Volvos. I don't know how widely it occurs but I guess far more, people not realising it and just being able to force their engines to start again.

I've not read widespread discussion of preventing this, eg sealing intakes, even sticking some dessicate pouches up them. I'm guessing it was more of a problem with older engines. What I would say is not to spray WD40 into them as this actually seems to wash away the more protective lubrication (my guess). As in, it was suggested to me that I should, and the problem occured afterwards.

 

[BabaYaga]

open the seawater pump, which drains everything. Heat exchangers will drain either forward or aft.

This may be true for some engines/installations, but not for all.
On mine, a Beta 20 hp with a propshaft and therefore tilted perhaps 10 degrees aft, simply draining the raw water circuit would still leave water standing in the lower part of the heat exchanger tube stack. This is because of the design of the exchanger, where water both enters and exits at the rear end.
Some antifreeze (2 liters at 50 percent is plenty in my case) in the final run is a quick and cheap insurance against potentially expensive damage, IMHO.

 

[Euphonyx]

If the boat is out of the water, I thought it was the norm to just drain the raw water side down.
If it stays in the water, then do nothing unless it's in the Baltic!

Depends. Boats left in salt water where I am (53° North) dont tend to need winterisation. Boats on freshwater and inland definitely do need to be winterised (engine, water system, toilet system)... depends!!

 

[Spirit (of Glenans)]

I use the stuff which is safe for drinking water systems on the basis that I understood the ordinary anti freeze to be highly toxic in the marine environment.

See post #9 above.

 

[vyv_cox]

This may be true for some engines/installations, but not for all.
On mine, a Beta 20 hp with a propshaft and therefore tilted perhaps 10 degrees aft, simply draining the raw water circuit would still leave water standing in the lower part of the heat exchanger tube stack. This is because of the design of the exchanger, where water both enters and exits at the rear end.
Some antifreeze (2 liters at 50 percent is plenty in my case) in the final run is a quick and cheap insurance against potentially expensive damage, IMHO.

Why doesn't it run aft to the trap?

 

[BabaYaga]

Why doesn't it run aft to the trap?

There are two reasons why the heat exchanger does not self drain.
Firstly because of the design. Water enters to lower section of the tube stack, runs forwards, turns and then runs backwards along the upper tubes to the exit.
If the engine was installed horizontally (as with a sail drive), then the entire system would probably empty through the raw water pump if the impeller was removed. With the engine tilted aft (as is often the case with a prop shaft) there will be an uphill run for the water between the rear of the heat exchanger and the 'threshold' at front of the engine. Thus, water will be left standing in the lower part of the tube stack and in the tube along the engine top.
Secondly, why will it not run aft to the trap? Well, the water in the upper half of the tube stack might do so, if it were not for the fact that this is often where the anti siphon valve is installed. If so, the only way for the exchanger to self drain is by the impeller pump, which it will not fully do.

 

[TernVI]

There are two reasons why the heat exchanger does not self drain.
Firstly because of the design. Water enters to lower section of the tube stack, runs forwards, turns and then runs backwards along the upper tubes to the exit.
If the engine was installed horizontally (as with a sail drive), then the entire system would probably empty through the raw water pump if the impeller was removed. With the engine tilted aft (as is often the case with a prop shaft) there will be an uphill run for the water between the rear of the heat exchanger and the 'threshold' at front of the engine. Thus, water will be left standing in the lower part of the tube stack and in the tube along the engine top.
Secondly, why will it not run aft to the trap? Well, the water in the upper half of the tube stack might do so, if it were not for the fact that this is often where the anti siphon valve is installed. If so, the only way for the exchanger to self drain is by the impeller pump, which it will not fully do.

That makes no sense to me.
Take the hoses off the HE.
The water will mostly drain out.

 

[VicS]

That makes no sense to me.
Take the hoses off the HE.
The water will mostly drain out.

The HE on the OP's engine will not drain into the trap because the injection point is higher than the HE .
Taking the outlet hose off will only partly drain it due to the position of the outlet

It can however be drained via the water pump , which Vyv suggests as an alternative route . In any case if an engine is to be drained and not flushed with antifreeze the pump must be drained if freezing is a risk.

ITYWF that the OP's boat has a saildrive but if the same range of engines are fitted with a shaft drive gear box there is the additional need to drain the water from the gear box oil cooler.

However the procedure described in the Op's owners manual for winterising the engine is to flush the seawater circuit through with antifreeze. . No doubt why he was asking for advice on the type of antifreeze to use.

The CORRECT advice you should be giving is to follow the recommended procedure described in the owners manual for flushing the system with antifreeze.

 

[BabaYaga]

That makes no sense to me.
Take the hoses off the HE.
The water will mostly drain out.

Yes, you could do that. But I was commenting on this claim:

Exactly so. Flush through with fresh water, I tip 5 litres into the strainer once ashore, then open the seawater pump, which drains everything. Heat exchangers will drain either forward or aft.

My observation is that simply opening the seawater pump will not necessarily drain everything. It depends on the engine and installation.

 

[TernVI]

The HE on the OP's engine will not drain into the trap because the injection point is higher than the HE .
Taking the outlet hose off will only partly drain it due to the position of the outlet

It can however be drained via the water pump , which Vyv suggests as an alternative route . In any case if an engine is to be drained and not flushed with antifreeze the pump must be drained if freezing is a risk.

ITYWF that the OP's boat has a saildrive but if the same range of engines are fitted with a shaft drive gear box there is the additional need to drain the water from the gear box oil cooler.

However the procedure described in the Op's owners manual for winterising the engine is to flush the seawater circuit through with antifreeze. . No doubt why he was asking for advice on the type of antifreeze to use.

The CORRECT advice you should be giving is to follow the recommended procedure described in the owners manual for flushing the system with antifreeze.

The correct advice would not involve polluting the sea with antifreeze.

 

[RJJ]

The correct advice would not involve polluting the sea with antifreeze.

I think we have all agreed that. Bucket under the exhaust seems to work

 

[dankilb]

+1 for following Beta’s instructions (and using antifreeze even if/before also attempting to drain the system)

There are two places on our Beta 50 where water remains even if the impeller and/or hoses are removed: the lower ‘corner’ of the heat exchanger (as explained above) and the feed pipe that runs around the back of the engine.

A wet vac or compressed air would be required to drain these with full confidence.

I wouldn’t intentionally let coolant into the sea - but let’s just say that a few mechanics I know only recycle oils/brake fluid etc. I fear a splash or two from my exhaust (on the hard) is nothing compared to what goes down the drains elsewhere. Come to think of it - aren’t the same antifreeze additives in screen wash? Every blast of that presumably washes into the water course eventually.

 

[Greg2]

I usually fill the raw water system with this non-toxic anit-freeze when winterising. Two bottles will do a six cylinder Perkins M300TI.

I get the point made in post #9 but prefer to use something that has no effect on the environment but we are moored in fresh.

 

[lynallbel]

I use the stuff which is safe for drinking water systems on the basis that I understood the ordinary anti freeze to be highly toxic in the marine environment.

Iirc solar hot water panels use safe anitfreeze, might be a reasonably priced alternative?

 

[VicS]

I usually fill the raw water system with this non-toxic anit-freeze when winterising. Two bottles will do a six cylinder Perkins M300TI.

I get the point made in post #9 but prefer to use something that has no effect on the environment but we are moored in fresh.

But you are using a propylene glycol based antifreeze............. It has a low toxicity to humans and other mammals but it is no less environmentally unfriendly than ethylene glycol
The toxicity to aquatic life is similar to ethylene glycol

Iirc solar hot water panels use safe anitfreeze, might be a reasonably priced alternative?

ITYWF that is is propylene glycol , which has a similar toxicity to aquatic life as ethylene glycol

 

[VicS]

The correct advice would not involve polluting the sea with antifreeze.

Following the procedures described in the owners manual DOES NOT involve polluting the sea with antifreeze

The boat should be ashore,​

The system should be drained before re- launching the boat​

Used and drained antifreeze should be collected and taken to a proper disposal site​

 

[lynallbel]

But you are using a propylene glycol based antifreeze............. It has a low toxicity to humans and other mammals but it is no less environmentally unfriendly than ethylene glycol
The toxicity to aquatic life is similar to ethylene glycol


ITYWF that is is propylene glycol , which has a similar toxicity to aquatic life as ethylene glycol

Tbh I have no idea, I just assumed it was safe, as in the event of a heating coil failure the a/f would end up in the hot water tank itself and come out the household taps.

Edit, jsut checked where I got mine from, and you are spot on,

5 litres Solar Antifreeze.
Neat propylene glycol with additive package.
Recommended dilution 40% (providing total volume of 12 litres) for use in solar systems.
Should be sufficient for most single and double panel systems.
Liquid colour: Pink

Note to self, stop drinking the hot water!

 

[Daverw]

Just to add, that some additives include stuff to neutralise the toxicity of the propylene glycol and the effect makes it food safe, these are used commonly in refrigeration chiller circuits. Others are not based on glycol at all, i.e hycool