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Connecting two skin tanks


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I currently have two skin tanks, one connected to a beta 38, which provides propulsion and the other connected to a beta 35, which runs a genset.

The engines are never used simultaneously.

The beta 38 skin tank is undersized, and while this hasn't been an issue yet on canals I'd like to connect the two tanks to allow for more cooling capacity if on rivers/tidal. 

Would a simple connecting hose/pipe between the two tanks be sufficient enough to allow coolant to flow between the tanks, if it is of sufficient bore i.e. 28mm?

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Sounds feasible, but here's another suggestion to ponder: assuming your 38 also supplies your calorifier, tap into that circuit and add a small towel rail in the bathroom. Although my skin tank is fine on my Beta 43, I've done this downstream of my calorifier,  using full bore valves to feed it so it can be isolated and with a full bore valve as a bypass. It works beautifully with all valves wide open, but I would be able to adjust if it was stealing too much engine heat. There's no engine temp issue and the calorifier heats up just fine.  As well as dumping a bit of extra heat for you, you'd have nice warm towels and/or a warmer bathroom which isn't an issue even in summer.  Mine's 400 x 300 iirc, but a myriad of sizes are available if you need to lose more heat, although it sounds like you are only adding a bit for belt and braces.  Just another option to consider.

Additionally,  whilst adding the second skin tank would bring the desired extra cooling for the 38 (which may be too much) it would also add lots more to presumably the quite happy 35 - which probably would then be running too cool. 

Edited by Sea Dog
35 cool running
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1 hour ago, Sea Dog said:

Sounds feasible, but here's another suggestion to ponder: assuming your 38 also supplies your calorifier, tap into that circuit and add a small towel rail in the bathroom. Although my skin tank is fine on my Beta 43, I've done this downstream of my calorifier,  using full bore valves to feed it so it can be isolated and with a full bore valve as a bypass. It works beautifully with all valves wide open, but I would be able to adjust if it was stealing too much engine heat. There's no engine temp issue and the calorifier heats up just fine.  As well as dumping a bit of extra heat for you, you'd have nice warm towels and/or a warmer bathroom which isn't an issue even in summer.  Mine's 400 x 300 iirc, but a myriad of sizes are available if you need to lose more heat, although it sounds like you are only adding a bit for belt and braces.  Just another option to consider.

Additionally,  whilst adding the second skin tank would bring the desired extra cooling for the 38 (which may be too much) it would also add lots more to presumably the quite happy 35 - which probably would then be running too cool. 

How can a thermostatted engine run too cool?

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Follow the flow pipe from the main engine to (hopefully)  the top of its tank.  Connect the bottom of that tank to the top of the second one ( where the other engine should be feeding in) and then  the bottom of the second tank back to the  main engine as well as to the other engine.

Don't worry about over cooling the main engine- the thermostat will take care of that, assuming one is fitted.

Caveats. 

Make sure you can fully vent both skin tanks in the new set-up.

You may need to install swing non-return valves or full-flow lever valves in both engines' return lines to ensure that the water goes where it is wanted.

The main engine circulation pump may or may not be happy with the extra flow restrictions.  It will probably be OK provided the inter-tank pipe is a decent size (bigger is better) and all the bends are reasonably gentle.

Both engines will have be part of the same cooling circuit, so the lowest header tank is likely to overflow. You can get sealing caps if it has the standard car radiator  type cap.   Top up via the highest tank

Flush well and renew the antifreeze completely unless you are sure both engines are on the same type of antifreeze.

 

N

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28 minutes ago, system 4-50 said:

How can a thermostatted engine run too cool?

No, you're right. I wandered off my thought train on the effects of adding a rad in the calorifier circuit and mistakenly extended the effects onto the 35! :D

I'd still be a bit reluctant to break into the perfectly happy 35 cooling circuit because of an unproven worry that the 38 cooling might need beefing up. 

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26 minutes ago, BEngo said:

 

Caveats. 

Make sure you can fully vent both skin tanks 

Thanks, just checking what you mean by fully vented? Do you mean in order to bleed them when re-filling? (both tanks have bleed points) otherwise, the coolant is vented at  the engines' header tanks. 

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1 hour ago, towpathrider said:

Thanks, just checking what you mean by fully vented? Do you mean in order to bleed them when re-filling? (both tanks have bleed points) otherwise, the coolant is vented at  the engines' header tanks. 

Yes. I meant get all the air out. The existing vents/bleed points should be fine.

N

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5 hours ago, Sea Dog said:

Additionally,  whilst adding the second skin tank would bring the desired extra cooling for the 38 (which may be too much) it would also add lots more to presumably the quite happy 35 - which probably would then be running too cool. 

Sorry, but that makes no sense.

If the engine has a correctly working thermostat, it is simply impossible to overcool it.  With a thermostat you simply can't have a "too big" skin tank.

EDIT:

Sorry should have read on - I see several others made the same point!

Edited by alan_fincher
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5 hours ago, alan_fincher said:


EDIT:

Sorry should have read on - I see several others made the same point!

Well, 4-50 did, but I back-pedalled pretty quick and explained myself before I got flamed too badly!  That bit was rubbish though, so I'll also take your shot on the chin. :blink:

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