emergency conversion fresh water pump to raw water?

[Russian007]

Originally Posted by Patrick of M

I think theoretically many engines would be convertible, but honestly, carrying a spare water pump sounds like a simpler solution.

In rolling seas that would be impossible and would take hours. This could be done with the throw of a gate valve on the fly. Seamless.

[Russian007]

Originally Posted by rslifkin

It's not that simple. On my engines, you'd have to make a few plumbing changes, but more importantly, unless the heat exchanger literally blew up, I can't think of anything that could fail where just switching to raw water cooling would actually help the situation.

My fresh water pump seized. Engine overheated, fan belt started burning, wheelhouse filled smoke. A preplumbed gated Y could've instantly solved the problem.

[rslifkin]

Originally Posted by Russian007

My fresh water pump seized. Engine overheated, fan belt started burning, wheelhouse filled smoke. A preplumbed gated Y could've instantly solved the problem.

Not necessarily. On many engines the stopped fresh water pump would majorly restrict flow and you'd still have serious cooling problems. And you're talking about extra plumbing that can fail and at least 2 valves on the simplest of systems, but more than 2 on many engines.

It's also very rare for a coolant pump to seize like that without leaking first. I'd call that a very minor concern. And even if you had valves, you'd have to let the engine cool to avoid cold shocking it, which can crack blocks and heads. Plus, you'd still need to sort out the belt drive to make sure the raw water pump is still turning.

I'm going to put this one down as a dumb idea. Not useful in the real world and full of logistical problems.

[Russian007]

Originally Posted by rslifkin

Not necessarily. On many engines the stopped fresh water pump would majorly restrict flow and you'd still have serious cooling problems. And you're talking about extra plumbing that can fail and at least 2 valves on the simplest of systems, but more than 2 on many engines.

It's also very rare for a coolant pump to seize like that without leaking first. I'd call that a very minor concern. And even if you had valves, you'd have to let the engine cool to avoid cold shocking it, which can crack blocks and heads. Plus, you'd still need to sort out the belt drive to make sure the raw water pump is still turning.

I'm going to put this one down as a dumb idea. Not useful in the real world and full of logistical problems.

You're right. Fresh water pump seizure is a "very minor concern" as you put it. Never happens and isn't an issue if it does.

[rslifkin]

Originally Posted by Russian007

You're right. Fresh water pump seizure is a "very minor concern" as you put it. Never happens and isn't an issue if it does.

It's a rare issue, and if it happens, just trying to dump the coolant and force raw water through the engine with a seized pump in the way is unlikely to be an effective solution. I'd rather carry a spare pump.

[skipperpete]

I’m interested, circulating pumps fail fairly frequently especially when the pulley side loads are increased by high output alternators. The failure need not be as spectacular as a bearing collapse or seizure, even a broken pulley could instantly stop circulation so what do y’all think about installing an electric pump in the coolant circuit, maybe by extending the hose between the circ pump and heat exchanger. I know this is dependent on how the coolant circuit is plumbed on the specific engine and the flow is partially restricted by the stationary impeller but I suspect that removing the thermostat will allow circulation through the bypass circuit if it can’t get past the stopped impeller.
The 12 volt pump is easy to find, some of the hybrid cars have been using em for years and the performance car guys also use them BUT in a moment of desperation mid doldrums I think I might try using a bilge pump in a bucket at or above the heat exchanger. Fill the bucket and put an extended hose from the block return in the bucket with the pump and the outlet from the bilge pump to the heat exchanger via that extended hose. This should work in theory but there still remains the problem with the loss of belt drive for the alternator and raw water pump so that needs a re think too[emoji848]. There’s a possibility that the coolant cap could leak too but I think it avoids the use of raw water through the fresh side. Davies Craig and Prius auto are two of the pumps I have in mind.
What do you think[emoji780][emoji780]

[rslifkin]

Originally Posted by skipperpete

I’m interested, circulating pumps fail fairly frequently especially when the pulley side loads are increased by high output alternators.

It definitely happens, although typically the worn bearings will cause the seals to leak and you'll see coolant drips from the weep hole on the pump long before any catastrophic failure.



That said, electric pumps are a viable option, or going to a serpentine belt that needs far less tension and is easier on the bearings (note that serp belt driven water pumps on modern engines tend to last a long time).



Realistically, there's no magic bullet for a cooling system that can't fail. And in my experience, the bulk of the sudden failures are on the raw water side (sucked junk into the intake and plugged the strainer or a failed impeller).


Issues like this are why I consider redundant propulsion on a powerboat more important in a coastal setting. In open water with tons of sea room, waiting an hour or 2 for stuff to cool a bit so you can fix it isn't the end of the world typically. In a more crowded or confined coastal area, redundant propulsion is the difference between "drop the anchor now, hope we don't get into a dangerous situation in the process and fix it right here" vs "move the boat to a suitable spot to stop and fix the issue".

[skipperpete]

I totally agree with redundant propulsion on single engine power boats but the only production boat that I’ve seen with this is Nordhavn.
A leaking circulation pump seal can be as debilitating for the engine as any of the other failure modes and the leak must be plugged to use my Prius pump plan but once the pump is dry and not spinning there are numerous emergency solutions ( 5200 FC might work) ...... remember, this emergency is at say, Chagos or some other remote location and the “fix” is a hypothetical discussion.
To be true to the OP ......... salt water could be used in my suggested cooling loop and instead of a closed loop one end could go overboard and the supply could be from a thru hull but I really hate the idea of running raw water through the fresh side of the cooling system.
It occurred to me that a bilge pump in plan B might not be rated for continuous duty so there’s that problem too.
The obvious solution is to simply carry a spare circulating pump.... just not if you have a Volvo 2003
Pete.

[Russian007]

Originally Posted by skipperpete

I’m interested, circulating pumps fail fairly frequently especially when the pulley side loads are increased by high output alternators. The failure need not be as spectacular as a bearing collapse or seizure, even a broken pulley could instantly stop circulation so what do y’all think about installing an electric pump in the coolant circuit, maybe by extending the hose between the circ pump and heat exchanger. I know this is dependent on how the coolant circuit is plumbed on the specific engine and the flow is partially restricted by the stationary impeller but I suspect that removing the thermostat will allow circulation through the bypass circuit if it can’t get past the stopped impeller.
The 12 volt pump is easy to find, some of the hybrid cars have been using em for years and the performance car guys also use them BUT in a moment of desperation mid doldrums I think I might try using a bilge pump in a bucket at or above the heat exchanger. Fill the bucket and put an extended hose from the block return in the bucket with the pump and the outlet from the bilge pump to the heat exchanger via that extended hose. This should work in theory but there still remains the problem with the loss of belt drive for the alternator and raw water pump so that needs a re think too[emoji848]. There’s a possibility that the coolant cap could leak too but I think it avoids the use of raw water through the fresh side. Davies Craig and Prius auto are two of the pumps I have in mind.
What do you think[emoji780][emoji780]

It's 100% viable and there are pumps made for just this. Some make the conversion permanent. I would suggest preplumbing and prewiring it. It varies from engine to engine, but at least in my case it's a 30 minute job. Murphy's law dictates the pump failure won't occur in the doldrums far from land but in heavy seas in the shipping land or 500 meters from the surfline. Thinking you can crawl into the bilge, wait 2 hours for the engine to cool, peeling back the alternator and other parts and replacing a failed pump with an OEM replacement part then putting it all back together the fantasy armchair captains.

[Patrick of M]

This thread started as "your pump craps out at the edge of the world" . I presumed that meant far from spare parts etc. So a spare seems a simple solution..... All WP do fail eventually.
If the "the edge of the world" means the actual edge of the flat earth, depicted in old charts as a waterfall of sorts with monsters writhing at the base, I suggest entreating some mermaids to harness the local fish or dolphins and tow you to safety.

[rslifkin]

Originally Posted by Russian007

Murphy's law dictates the pump failure won't occur in the doldrums far from land but in heavy seas in the shipping land or 500 meters from the surfline. Thinking you can crawl into the bilge, wait 2 hours for the engine to cool, peeling back the alternator and other parts and replacing a failed pump with an OEM replacement part then putting it all back together the fantasy armchair captains.

That, right there is exactly why I'm of the opinion that redundant propulsion (twins or a wing engine) is far more important for coastal cruising than ocean crossing. A failure is generally a much more immediate problem in coastal settings, so the ability to keep moving to a safe spot to make repairs is very helpful.

[deblen]

Originally Posted by rslifkin

That, right there is exactly why I'm of the opinion that redundant propulsion (twins or a wing engine) is far more important for coastal cruising than ocean crossing. A failure is generally a much more immediate problem in coastal settings, so the ability to keep moving to a safe spot to make repairs is very helpful.

Bring your boat to safety by using your outboard/dinghy in a hip tow. Lock the outboard straight & steer from the mother ship in open water. Works well.

[rslifkin]

Originally Posted by deblen

Bring your boat to safety by using your outboard/dinghy in a hip tow. Lock the outboard straight & steer from the mother ship in open water. Works well.

Given a dinghy with a reasonable size outboard and the ability to launch it fairly quickly, yes, that's also an option. Definitely better than having to drop the hook and fix the issue right where you sit.

[FPNC]

When you, 'travel to the edge of the world', you carry a spare water pump.

[deblen]

Originally Posted by rslifkin

Given a dinghy with a reasonable size outboard and the ability to launch it fairly quickly, yes, that's also an option. Definitely better than having to drop the hook and fix the issue right where you sit.

A friend & I brought his Southern Cross 28 over 50mi. up the Maine coast with a 5HP Honda on 11Ft Avon.Running The Honda abt 1/2 throttle gave us 5.5-6 kts-same speed as her 12HP diesel made. Once we got going,clear of obstacles,we locked the Honda straight ahead & steered by tiller. Went well.