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New skin tank or not


Martin44

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Hi guys,

 

my boat is due for blacking this month and I am currently pondering if I will have a bigger skin tank on outside swim fitted at the same time.

Ever since I took it on rivers from canals the engine's been overheating, running into the 100C and higher.

So my question is before I do have fitted a new skin tank, what else could it cause.

 

I have let the air out through the vent 

changed thermostat for new one

 

but still overheats.

 

I have Beta Marine BD1005 (approx. 28hp)  engine on 45' narrowboat. Measured the skin tank at 6 ft sq.

 

I had an engineer over to check it out and he thinks it needs bigger tank than I currently have

 

Any suggestions appreciated.

 

Thank you

 

Best Wishes

Martin

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1 minute ago, Robbo said:

If you do find you need a bigger tank but don’t want to go down that line. A heat exchanger using raw water maybe another option.

I don't mind going for a new tank. My worry is that it isn't the cause for overheating and even after having fitted new one the problem persists. The new tank would be done Fox narrowboats and it is similar to this: http://noproblem.org.uk/blog/so-here-we-go-first-though-the-cooling-system/

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I had exactly the same problem on my 45 ft narrowboat with a BMC 1.5 engine . The problem was cured by replacing the skin tank cooling with two pipes along the swim . The late Charlie Fox had this type of cooling on all his narrowboats and there is an added bonus that the new system is not pressurised . I had mine modified at Foxes boatyard in March and it has never gone over 80 degrees since . 

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1 minute ago, Troyboy said:

I had exactly the same problem on my 45 ft narrowboat with a BMC 1.5 engine . The problem was cured by replacing the skin tank cooling with two pipes along the swim . The late Charlie Fox had this type of cooling on all his narrowboats and there is an added bonus that the new system is not pressurised . I had mine modified at Foxes boatyard in March and it has never gone over 80 degrees since . 

Yes it would be done by Foxes. Also, it was suggested to me in another boatyard that it might not be the size of tank, because the temperature doesn't go down when I slow down from 1500 rpm to 1000 rpm.

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26 minutes ago, Martin Trnecka said:

I have Beta Marine BD1005 (approx. 28hp)  engine on 45' narrowboat. Measured the skin tank at 6 ft sq.

 

I had an engineer over to check it out and he thinks it needs bigger tank than I currently have

If it is properly designed, 6 square feet definitely sounds on the low side, but I'm not convinced disasterously so.

 

How thick is it?

Do you know for certain it has baffles in it?

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31 minutes ago, Martin Trnecka said:

Hi guys,

 

my boat is due for blacking this month and I am currently pondering if I will have a bigger skin tank on outside swim fitted at the same time.

Ever since I took it on rivers from canals the engine's been overheating, running into the 100C and higher.

So my question is before I do have fitted a new skin tank, what else could it cause.

 

I have let the air out through the vent 

changed thermostat for new one

 

but still overheats.

 

I have Beta Marine BD1005 (approx. 28hp)  engine on 45' narrowboat. Measured the skin tank at 6 ft sq.

 

I

The usual guidance is 1/4 to 1/3 square foot per horsepower, on which basis you need 7-9 square feet of tank. So you can get away with 6 sq ft on the canals when you aren't using full engine power, but on rivers the inadequacy of the skin tank shows up.

 

Blackrose of this forum had a second internal skin tank welded onto the inside of his widebeam on the opposite side to the original inadequate skin tank, and then plumbed the two in series. Might be a bit tight for space to do the same on a narrowboat though.

Edited by David Mack
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1 minute ago, alan_fincher said:

If it is properly designed, 6 square feet definitely sounds on the low side, but I'm not convinced disasterously so.

 

How thick is it?

Do you know for certain it has baffles in it?

According to the formula, it should be 7ft sq, but would 1ft make such a difference? The tank is about 1 inch thick. I don't know if it has baffles. Any way to find out?

2 minutes ago, David Mack said:

The usual guidance is 1/4 to 1/3 square foot per horsepower, on which basis you need 7-9 square feet of tank. So you can get away with 6 sq ft on the canals when you aren't using full engine power, but on rivers the inadequacy of the skin tank shows up.

 

Yes, it should be at least 7ft sq. So perhaps it the size which matters here.

 

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Just now, Martin Trnecka said:

According to the formula, it should be 7ft sq, but would 1ft make such a difference? The tank is about 1 inch thick. I don't know if it has baffles. Any way to find out?

7 sq feet still sounds small to me.

 

An extra square foot might help if it is on the margin, but I would go larger.

 

Depending on where the connections are, you might actually be able to see, or if you can't maybe you can poke things in and see if they come up against anything or not.

 

Who was the shell builder - some are known to have skimped in this area?

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Just now, alan_fincher said:

7 sq feet still sounds small to me.

 

An extra square foot might help if it is on the margin, but I would go larger.

 

Depending on where the connections are, you might actually be able to see, or if you can't maybe you can poke things in and see if they come up against anything or not.

 

Who was the shell builder - some are known to have skimped in this area?

It is a Reeves boat and what I know about history the boat, it lived on the canals.

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Innisfree had 6.5 sq ft and 40bhp,  hammered it up the Thames in hot summer with no trace of overheating. Max revs producing 40 bhp sat the boat down and created a massive bow wave, a total waste of fuel, it was just as good at two thirds of that. All you need max power for is emergency stopping,in any case Keith at Crowthers reckoned our prop absorbed about 25 bhp max. Original 30 bhp engine struggled slightly with large alternator on full output (about 8 bhp) which seemed to confirm all that. 

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53 minutes ago, Martin Trnecka said:

It is a Reeves boat and what I know about history the boat, it lived on the canals.

OK, Reeves are not one I'd associate with a history of poor skin tank design.

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1 hour ago, Martin Trnecka said:

Hi guys,

 

my boat is due for blacking this month and I am currently pondering if I will have a bigger skin tank on outside swim fitted at the same time.

Ever since I took it on rivers from canals the engine's been overheating, running into the 100C and higher.

So my question is before I do have fitted a new skin tank, what else could it cause.

 

I have let the air out through the vent 

changed thermostat for new one

 

but still overheats.

 

I have Beta Marine BD1005 (approx. 28hp)  engine on 45' narrowboat. Measured the skin tank at 6 ft sq.

 

I had an engineer over to check it out and he thinks it needs bigger tank than I currently have

 

Any suggestions appreciated.

 

Thank you

 

Best Wishes

Martin

It would be worthwhile to flush out the skin tank first to see if that gives you any improvement. I flushed my own out last year, a great deal of muck came out. 

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Thank you all for replying so far.

 

If I went down the route and had a new skin tank, would it have any influence on my current safety certificate? Would I need a surveyor to overlook this work and confirm that it still complies with safety regulations?

2 minutes ago, nbfiresprite said:

It would be worthwhile to flush out the skin tank first to see if that gives you any improvement. I flushed my own out last year, a great deal of muck came out. 

The coolant in the holding tank on top of the engine seems clean provided it would show that there is muck in.

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14 minutes ago, Martin Trnecka said:

Thank you all for replying so far.

 

If I went down the route and had a new skin tank, would it have any influence on my current safety certificate? Would I need a surveyor to overlook this work and confirm that it still complies with safety regulations?

The coolant in the holding tank on top of the engine seems clean provided it would show that there is muck in.

It may looked that, You find that the sides of the skin tank are covered in thick layer of build up which needs to be removed. My own looked cleared. Central heating needs to be flushed every so often as boilers along with engine rads to remove build up. 

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3 minutes ago, nbfiresprite said:

It may looked that, You find that the sides of the skin tank are covered in thick layer of build up which needs to be removed. My own looked cleared. Central heating needs to be flushed every so often as boilers along with engine rads to remove build up. 

Ok. Thanks, I will look into this. Now I need to find out how to make up the coolant solution? I guess there are outlets on the skin tank to let the coolant out. Sorry, I am totally ignorant about this.

Edited by Martin Trnecka
misspelling
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2 hours ago, David Mack said:

The usual guidance is 1/4 to 1/3 square foot per horsepower, on which basis you need 7-9 square feet of tank. So you can get away with 6 sq ft on the canals when you aren't using full engine power, but on rivers the inadequacy of the skin tank shows up.

 

Blackrose of this forum had a second internal skin tank welded onto the inside of his widebeam on the opposite side to the original inadequate skin tank, and then plumbed the two in series. Might be a bit tight for space to do the same on a narrowboat though.

Off the top of my head I think Beta say 1 sq ft per 4bhp, so that sounds good for 24bhp, which I bet if you look at the power curves you never get to, the max 28 will be at something like 3000rpm.  Ours is a Beta 35 which is 37.5bhp at 3000rpm, we never go over 2000rpm, so the max power it develops  at that is something like 25bhp, the skin tank is 8 sq ft I 5hink.  It will run all day on rivers/tidal rivers at 2000rpm.

 

So unless you are actually using the rpm to develop full power, it seems there is more than just tank area, but no doubt more tank area is going to help, I certainly wish the skin tank on ours had more margin.

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Just a quick check that your existing tank is plumbed in the right way round - hot from the engine in at the top, cold to the engine out at the bottom.  If it isn't, the natural flow of the cooling water falling in the skin tank will be against the flow of warming water rising through the engine, reducing efficiency. 

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30 minutes ago, john6767 said:

Off the top of my head I think Beta say 1 sq ft per 4bhp, so that sounds good for 24bhp, which I bet if you look at the power curves you never get to, the max 28 will be at something like 3000rpm.  Ours is a Beta 35 which is 37.5bhp at 3000rpm, we never go over 2000rpm, so the max power it develops  at that is something like 25bhp, the skin tank is 8 sq ft I 5hink.  It will run all day on rivers/tidal rivers at 2000rpm.

 

So unless you are actually using the rpm to develop full power, it seems there is more than just tank area, but no doubt more tank area is going to help, I certainly wish the skin tank on ours had more margin.

The engine is actually 28hp, but that probably does not have much influence anyway. The beta marine website also has a table what engine size is required for what length of boat. My engine is actually undersized for my boat according to the table. 

Also I rarely run it more than 1500 rpm.

11 minutes ago, Sea Dog said:

Just a quick check that your existing tank is plumbed in the right way round - hot from the engine in at the top, cold to the engine out at the bottom.  If it isn't, the natural flow of the cooling water falling in the skin tank will be against the flow of warming water rising through the engine, reducing efficiency. 

Yes, it is the right way: hot in in upper corner; cold in in lower corner

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19 minutes ago, Martin Trnecka said:

Yes, it is the right way: hot in in upper corner; cold in in lower corner

That would have been too easy, wouldn't it!  Ok, last chance at the cheap and easy fixes - what's your anti freeze strength?  Beta recommend 30% iirc and definitely no more than 50% as the cooling capacity gets lower as strength increases.

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How thick is the blacking on the outside of the tank? If there are many layers of bitumen it could be quite thick, which would reduce the heat transfer. You might get away with stripping the area of the tank right back to bare metal before applying the new blacking.

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24 minutes ago, Sea Dog said:

That would have been too easy, wouldn't it!  Ok, last chance at the cheap and easy fixes - what's your anti freeze strength?  Beta recommend 30% iirc and definitely no more than 50% as the cooling capacity gets lower as strength increases.

That I don't know. I bought the boat in Feb and so far did not change the coolant.

6 minutes ago, David Mack said:

How thick is the blacking on the outside of the tank? If there are many layers of bitumen it could be quite thick, which would reduce the heat transfer. You might get away with stripping the area of the tank right back to bare metal before applying the new blacking.

That's what  I was asking the engineer, he thought it would have not much bearing, but of course you might be right.

The boat was built in 1997 and I don't think it was ever striped to bare metal. The files on the boat show me that it was regularly blacked-every 2-3 years.

Edited by Martin Trnecka
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Would suggest you also check the thickness of paint on the outside of the boat in the tank area. Some coatings are very good insulators and at a boatyard where I worked we used to regularly scrape off excess thickness which caused the trouble you have found

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7 minutes ago, nbfiresprite said:

Another thing to check is the coolant hose. these can became partly blocked due to collapsing within the hose with no sign on the outside.

 

I don't quite follow. What to look for in the hose?

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