Advice needed on over heating engine

[WotEver]

1 minute ago, Mike the Boilerman said:

 

If the OP fits a new one the correct size on the outside, there is no need to remove the old one from the inside. 

Apart from tidiness and a tad more working space around the engine. 

[MtB]

Just now, WotEver said:

Apart from tidiness and a tad more working space around the engine. 

 

Removing an internal skin tank will make an unholy mess in the engine bay with a grinder or gas axe, and for what? It is hardly in the way, looking at the photo.

[blackrose]

Most widebeams with bigger engines are fitted with 2 skin tanks - one on the inside of each swim, connected in series. They do this because there simply isn't enough surface area on the inside for a single tank that would be sufficient for a big engine. As far as I'm aware these boats have no higher incidence of airlocks occuring than narrow boats with single skin tanks.

 

My boat was fitted with one tank as it only had a 55hp engine, but it needed two. My mate has the same boat with an Isusu 70 (65hp) and that came with 2 skin tanks as standard, connected in series (no airlocks). I don't have any problems of airlocks on my boat either since I fitted the additional tank.

 

I really don't see what the point would be in getting rid of the existing tank? I'd keep it and have a new one installed on the outside of the other swim as that is the only option that gives you the ability to utilise both if required. All this talk of cutting out the existing tank is madness in my opinion!

1 hour ago, Mike the Boilerman said:

 

Removing an internal skin tank will make an unholy mess in the engine bay with a grinder or gas axe, and for what? It is hardly in the way, looking at the photo.

You gain an inch of space along the swim... I guess in a narrowboat engine hole that matters! ?

Edited August 12, 2018 by blackrose

[nb Innisfree]

With a well designed and fitted cooling system there should never be any air locks, all air should find its way to the highest point. Innisfree had/has a 6.5 sq ft skin tank with 40 bhp and never overheated, it was borderline but coped because the pipe runs were big enough diameter and correctly installed with no air trapped anywhere. I  doubt 7.5 sq ft could have been exceeded without incursion into cabin space but it would have given a reasonable margin. 

Edited August 12, 2018 by nb Innisfree

[ditchcrawler]

If you put a new large tank on the outside of the swim partly over the internal one could you not  just put 2 sensibly placed holes from the old to new through the hull to connect them. this is working on the basis that the old one is baffled, or even one hole and a single new connection plugging one connection on the old one.

[blackrose]

46 minutes ago, ditchcrawler said:

If you put a new large tank on the outside of the swim partly over the internal one could you not  just put 2 sensibly placed holes from the old to new through the hull to connect them. this is working on the basis that the old one is baffled, or even one hole and a single new connection plugging one connection on the old one.

But the covered part of the original tank won't work as a heat exchanger because there's nothing cold on the other side and the overlap area on both tanks will have a greater volume and thermal mass, hence reduced efficiency in shedding that heat.

 

Two separate tanks would be more efficient. A proven design is already there. Just look at widebeams and some narrowboats with dual skin tanks - one on each swim plumbed in series. Why reinvent the wheel? 

[alan_fincher]

8 hours ago, Mike the Boilerman said:

 

Removing an internal skin tank will make an unholy mess in the engine bay with a grinder or gas axe, and for what? It is hardly in the way, looking at the photo.

 

7 hours ago, blackrose said:

I really don't see what the point would be in getting rid of the existing tank? I'd keep it and have a new one installed on the outside of the other swim as that is the only option that gives you the ability to utilise both if required. All this talk of cutting out the existing tank is madness in my opinion!

You gain an inch of space along the swim... I guess in a narrowboat engine hole that matters! ?

 

Provided the fabricator made it 1" thick.  In our old boat it was 4" thick.  Removing it allowed you to be able to stand down the hole on that side of the engine - quite impossible before we did.

Many boat engines seem to expect the "plumbing" and skin tank to be on a certain side.  I'm not sure if this is always the left, but it seems to be that way much of the time.  If you have a cruiser stern (or semi-trad), then I guess it doesn't cause too many issues if you add a tank on the other side, and have the pipes passing across the engine bay.

However we had a "trad" boat where you stepped down into a space to the right of the engine to access the cabin.  If we had added a skin tank to the right hand side of the boat, the pipes would naturally have needed to pass across this lowered walk way, so it would have been impractical, other than by having pipes that dipped down far lower than one would want, and where any natural thermosyphoning was lost.

If you can provide a large enough external tank on the existing swim there is no downside to disabling or removing the existing one.  I'm with Tony that you are far less likely to suffer any air lock / bleeding problems if there is only one.  I fully accept your solution has worked fine for you, but I can imagine situations in a narrow boat where it might not.  "Keep it simple" is always best, to my mind.

[Michael Quelch]

So after a bit of thinking and looking at the advice on here one option that I might go for is to fit another skin tank on the other swim, looking at the room internally I can get a good 4 foot area. My plan will be to get it fabricated as a complete tank with steel on both sides and then fillet weld it into place, making sure that before its fitted I use a thermal paste or substance to fill any air between the two steel plates, I believe this should give me the extra cooling I need but without having to worry about getting the welder into the tight space to get a full seam weld.

 

What's your thoughts on this solution as it would mean that we don't have to have her out of the water and it is better than adding a car rad like I did think about?

[MtB]

Have you seen the price of thermal paste???? 

 

About a fiver for 10ml and you’ll probably need half a litre. 

[David Mack]

43 minutes ago, Michael Quelch said:

So after a bit of thinking and looking at the advice on here one option that I might go for is to fit another skin tank on the other swim, looking at the room internally I can get a good 4 foot area. My plan will be to get it fabricated as a complete tank with steel on both sides and then fillet weld it into place, making sure that before its fitted I use a thermal paste or substance to fill any air between the two steel plates, I believe this should give me the extra cooling I need but without having to worry about getting the welder into the tight space to get a full seam weld.

 

What's your thoughts on this solution as it would mean that we don't have to have her out of the water and it is better than adding a car rad like I did think about?

 

No with 2 thicknesses of steel between the cooling water and that canal water you will get much less heat transfer - even if the thermal paste does its job. A new internal tank must have the existing shell plating as it's outside face - as in Blackrose's photo earlier in the thread.

[MtB]

5 minutes ago, David Mack said:

 

No with 2 thicknesses of steel between the cooling water and that canal water you will get much less heat transfer - even if the thermal paste does its job. A new internal tank must have the existing shell plating as it's outside face - as in Blackrose's photo earlier in the thread.

 

I’m inclined to disagree. The OP only needs a marginal increase in cooling capacity and his proposal may well do the trick quickly and easily. There is a small risk however that his pasted on tank (which need only be say 16swg steel) still won’t be good enough. Some proper calculations would be a good predictor though. 

[alan_fincher]

I don't think it will work, and would strongly advise against it.  The likelihood that the new tank will exactly match the profile of the swim it is being added to seems slight to me, and I would expect this to be a most unpredictable arrangement.

 

It might work, but I fear it is far more likely it will not.

 

This isn't an area to skimp on, IMO.

 

If you are in trouble on a river and the engine starts to boil over, you tend to be a bit out of options.

I'd do the job properly, and avoid likely problem situations until I knew I had.

[Boater Sam]

Why not construct the extra skin tank on the outside of the opposite swim? Easy to weld and if not more than 20mm thick will not upset the swim of the hull. Or even a cooling pipe externally under the uxter plate as was suggested in a previous thread.

[Alan de Enfield]

1 hour ago, Michael Quelch said:

What's your thoughts on this solution

The correct solution is not to do a bodge - but to do it properly.

Bite the bullet, have her lifted out and weld on either another tank, or, a pipe around the swim.

 

One day you may be on a River that has a bit of flow on it, has weirs and is known for boats going over the weirs.

Do you really want a bodge cooling system to fail at the worst possible time ? (Murphy's Law)

When you sell the boat and the new owner, unsuspecting that a bodge was done is crossing the Wash …………………………..

 

Boats are not ideal for those who wish to skimp & bodge.

[Michael Quelch]

It is def not a case of bodging it, it’s more about looking for the most cost effective solution, we live on the boat and the closest place to pull her out is booked up for months and also it’s about a days travel away. 

 

if the only solution is to wait until next year and have her out of the water that’s fine but I am looking for alternatives, engines are cooled in various ways through raw water, skin tanks and air these are not classed as  bodges I’m asking people advice on potential alternative ways to cool her for the time being that is safe.

[Robbo]

1 minute ago, Michael Quelch said:

It is def not a case of bodging it, it’s more about looking for the most cost effective solution, we live on the boat and the closest place to pull her out is booked up for months and also it’s about a days travel away. 

 

if the only solution is to wait until next year and have her out of the water that’s fine but I am looking for alternatives, engines are cooled in various ways through raw water, skin tanks and air these are not classed as  bodges I’m asking people advice on potential alternative ways to cool her for the time being that is safe.

 

I haven't kept up with the thread, but if you have central heating and radiators then just get a heat exchanger and pump.   Cheap, effective and useful (bar summer!).

[Michael Quelch]

I already have a circulation pump for three radiators running the length of the boat to the back boiler on our squirrel stove. So could easily fit a heat exchanger into the circuit not to worried about the interior of the boat getting warm as that’s easily vented and would be free extra heating in the winter lol

 

That could be a potential option thank you. 

 

 

[Robbo]

37 minutes ago, Michael Quelch said:

I already have a circulation pump for three radiators running the length of the boat to the back boiler on our squirrel stove. So could easily fit a heat exchanger into the circuit not to worried about the interior of the boat getting warm as that’s easily vented and would be free extra heating in the winter lol

 

That could be a potential option thank you. 

 

 

Go overboard on the exchanger, the ratings are for when there is a large difference in water temperature.  The ratings drop the closer the difference is.

 

also have the exchanger higher than the engine so your not gravity heating the engine when you have the stove on in winter.

Edited August 13, 2018 by Robbo

[Michael Quelch]

What size would you recommend, also where is best to get them from as seen a few on ebay but going for silly money, the stove I have is putting out about 5kw in power which should have been matched to the rads giving around 12000 btu's. hopefully someone on here may be able to work out how much additional cooling this can provide the engine cooling system, am I right in thinking that you would want it plumbed into the engine skin tank and not the collarifier circuit due to the greater circulation of water?

[MtB]

17 minutes ago, Michael Quelch said:

What size would you recommend, also where is best to get them from as seen a few on ebay but going for silly money, the stove I have is putting out about 5kw in power which should have been matched to the rads giving around 12000 btu's. hopefully someone on here may be able to work out how much additional cooling this can provide the engine cooling system, am I right in thinking that you would want it plumbed into the engine skin tank and not the collarifier circuit due to the greater circulation of water?

 

I would suggest a 100kW plate heat exchanger, bering in mind Robbo's comment about the heat transfer plummeting with the temperature differential 

 

These cost about £100 normally, and are about 400 x 80 x 80mm.

[Tony Brooks]

26 minutes ago, Michael Quelch said:

What size would you recommend, also where is best to get them from as seen a few on ebay but going for silly money, the stove I have is putting out about 5kw in power which should have been matched to the rads giving around 12000 btu's. hopefully someone on here may be able to work out how much additional cooling this can provide the engine cooling system, am I right in thinking that you would want it plumbed into the engine skin tank and not the collarifier circuit due to the greater circulation of water?

5kW = 5000W. 750W more or less = 1hp. So 5000/750 = 6.67 HP.  Therefore as long as the rads are matched to the stove they would in theory take about 6.67 hp's worth of heat out f the system so aobut 1.5sq ft of skin tanks worth. However the higher the ambient temperature in the cabin the less heat will be transferred into the air. In my view still a bode.

 

In my view you can gravel for days and days at this time of year without overheating the engine now you know the likely reason so having the yard  a day's cruise away seem like an excuse not to get it done. Plenty of other yards around,  especially on the canals who probably understand narrowboats better than many river yards.

 

You have been given the best advice abut a tank on the outside of the swim or pipes around the swim but of course you are free to ignore it but please think a little before you try to get others to get involved with your schemes.

Edited August 13, 2018 by Tony Brooks

[nb Innisfree]

I plumbed the engine coolant circuit into the CH circuit via a  two way valve, if a overheating situation arose I could divert coolant through CH rads as a heat dump (though such a situation never arose) It turned out that if I used the engine to heat CH the engine pump managed to circulate coolant ok but with enough resistance to allow a quick engine warm up. Also Mikuni could be used to pre-heat engine, very handy in cold weather and allowed engine to reach operating temp in just a few mins. 

[Tacet]

6 hours ago, Tony Brooks said:

5kW = 5000W. 750W more or less = 1hp. So 5000/750 = 6.67 HP.  Therefore as long as the rads are matched to the stove they would in theory take about 6.67 hp's worth of heat out f the system so aobut 1.5sq ft of skin tanks worth. However the higher the ambient temperature in the cabin the less heat will be transferred into the air. In my view still a bode

Some of the engine's horsepower ought to be consumed in propelling the boat

[MtB]

3 minutes ago, Tacet said:

Some of the engine's horsepower ought to be consumed in propelling the boat

 

 

From the depths of my memory I seem to recall a diesel is approx 50% efficient, i.e. of the energy being used in fuel, about half results in shaft output HP and the other hlfresults in heat and noise - mostly heat. So for any given engine, the shaft power output is roughly equal to the heat power output, and the heat power output needs to be dumped through the cooling system. This is why Tony is using the power output of the engine as a proxy for the heat transfer power to cool it, I suspect. 

[Robbo]

8 minutes ago, Mike the Boilerman said:

 

 

From the depths of my memory I seem to recall a diesel is approx 50% efficient, i.e. of the energy being used in fuel, about half results in shaft output HP and the other hlfresults in heat and noise - mostly heat. So for any given engine, the shaft power output is roughly equal to the heat power output, and the heat power output needs to be dumped through the cooling system. This is why Tony is using the power output of the engine as a proxy for the heat transfer power to cool it, I suspect. 

Believe most of the heat is lost via the exhaust tho.