My overheating problems.

[RobinJ]

Pardon my higgerance, but what is the purpose of these baffles? Our boat has a keel-cooled engine so I assume that it has a skin tank (and therefore baffles).

Part of the reason why flow tends not to be important is that water flows by the shortest route, so without baffles trys to take a diagonal route between inlet and outlet. It is complicated by the fact that hot water rises, so can only fall to the outlet as it cools, or is at least as cold (or hot) as the water around it.

With baffles the water is forced to flow in a particular pattern (up and down or across and back), thereby spending more time in the skin tank and in theory loosing more heat! Up and down baffles work, but the flow is upset by the natural convection of hot water rising, cold water falling and works better with high flow rates!

[RLWP]

Part of the reason why flow tends not to be important is that water flows by the shortest route, so without baffles trys to take a diagonal route between inlet and outlet. It is complicated by the fact that hot water rises, so can only fall to the outlet as it cools, or is at least as cold (or hot) as the water around it.

With baffles the water is forced to flow in a particular pattern (up and down or across and back), thereby spending more time in the skin tank and in theory loosing more heat! Up and down baffles work, but the flow is upset by the natural convection of hot water rising, cold water falling and works better with high flow rates!

 

Convection currents in a pumped system? Are you sure?

 

Richard

[bizzard]

Hi,

 

Hopefully the baffles produces a more convulated path for the water to follow meaning that it has more exposure to cooling surfaces.

 

My experience of cooling/overheating in these circumstances found that water was flowing through the cooler too quickly and an adjustemnt of pump pulley size overcame the problem.

 

Best of Luck.

 

Leo

That could also be tried easily with a G clamp and a couple of bits of wood to restrict the flow at a hose.

[RLWP]

That could also be tried easily with a G clamp and a couple of bits of wood to restrict the flow at a hose.

 

Neat!

 

Richard

[Albion]

Or, of course, has baffles, but simply not big enough to sustain prolonged use of the engine on higher power settings.....

 

Are relatively modern LB boats known to come without baffles in the tank, then ? I'd have thought they built enough to get that bit of the design right ?

 

And you would have thought that South West Durham Steelcraft would have built enough to realise that baffles were essential but the gang that built my widebeam (and others) didn't which is why we suffered from overheating on long hard runs. It is also the reason that I suggested that the baffles might be missing. I am afraid to say that when the workforce get demoralised or aren't adequately supervised they can tend to take shortcuts where it doesn't show and skin tank baffles are one of those possible areas.

An investigation into the temperature gradient over the whole tank are will give a clue as to whether there are baffles or not if you can't see the weld distortions from the tacking of the baffles.

Roger

[RobinJ]

Convection currents in a pumped system? Are you sure?

With vertical baffles, if the flow rate is low enough to allow convection to start, yes. This could easily happen at idle speeds?

Doesn't happen with horizontal baffles as convection works with the flow.

[RLWP]

With vertical baffles, if the flow rate is low enough to allow convection to start, yes. This could easily happen at idle speeds?

Doesn't happen with horizontal baffles as convection works with the flow.

 

He's unlikely to be having a problem at idle speeds though

 

Richard

[smileypete]

If it's idling quite hot, I'd try spraying a hose on the inner side, if the temp drops off that tells you something.

 

If it IS hot across the bottom, and it has top inlet and bottom outlet, it points to vertical baffles that are seriously letting by at the bottom.

 

cheers, Pete.

smpt

[RobinJ]

He's unlikely to be having a problem at idle speeds though

He's unlikely to have vertical baffles either

[bizzard]

We had a 10' wide Liverpool boat here a while ago which i used to service with the same Isuzu engine and i'm almost certain the inlet pipe was at the top and the outlet at the bottom. I did always get some trapped air from the tank top bleeder.

I have to do a service this week on i think its a Wilson 10' wide beam with the same Isuzu engine.i'll check its cooling system out and report.In fact the boats here and i can go and look any time.

I have to pop out soon to get some servicing stuff for this boat and will have a decko at it this afternoon. As i have permission and access to work on it at my leisure.

[Albion]

One quick question Blackrose, before going on further have you bled your skin tank using the little rusty looking bleed vent near the top skin tank connection? Apologies if you have already stated that you have 'cos it might well be buried in the vast number of postings on this topic.

Roger

[nicknorman]

One quick question Blackrose, before going on further have you bled your skin tank using the little rusty looking bleed vent near the top skin tank connection? Apologies if you have already stated that you have 'cos it might well be buried in the vast number of postings on this topic.

Roger

Having a lot of air at the top of the tank would certainly explain the otherwise inexplicable report that the tank is hotter at the bottom than at the top. Definitely worth trying to bleed it!

[bizzard]

Having a lot of air at the top of the tank would certainly explain the otherwise inexplicable report that the tank is hotter at the bottom than at the top. Definitely worth trying to bleed it!

Indeed but i think Mike has checked that several times.

 

Bags of ice cubes could be hung against the tank side to increase coolage. With a pint of Gin and tonic standing by. Every little helps.

 

Or Mike could invest in a sweet shop ice cream freezer and make his own ice cubes,enough to see him through on a long trip against tide or current.

Edited May 29, 2012 by bizzard

[MtB]

I'm sorry, Mike, but while I have previously seen people suggest similar, it completely goes against the facts.

 

If the flow rate is very low, then hot water entering the tank at the top will spend longer in the tank before it eventually finds its way to the bottom, for return back to the engine.

 

That means it spends longer on average against the cold outside of the tank, so will lose more temperature than if it were being pumped through faster.

 

Hence slow flow rate, if anything, results in a bigger temperature difference across the tank.

 

 

 

100% agreed. I dunno what I was thinking when I posted that! I blame the Muscadet

[bizzard]

An automatic ''Ice-cube dispenser mechanism''wired into the temperature gauge circuit that could be arranged above the header tanks filler that would drop ice cubes into it at regular intervals.

[alan_fincher]

And you would have thought that South West Durham Steelcraft would have built enough to realise that baffles were essential but the gang that built my widebeam (and others) didn't which is why we suffered from overheating on long hard runs.

Fair enough, and your argument is valid.

 

My "Evans and Son" (effectively "Mike Heywood") not only had an appallingly undersized tank, it also proved to have no baffles.

 

I'd have thougt LB were cleverer than that by the time Mikes was built, but of course it's possible even this has none.

[nicknorman]

An automatic ''Ice-cube dispenser mechanism''wired into the temperature gauge circuit that could be arranged above the header tanks filler that would drop ice cubes into it at regular intervals.

No, you are forgetting basic physics, the ice cube maker has to be powered by the engine alternator, so the increased power drain would cause the engine to produce more additional heat than the melting ice cubes would absorb. Bit like running a battery charger from the inverter!

[RLWP]

No, you are forgetting basic physics, the ice cube maker has to be powered by the engine alternator, so the increased power drain would cause the engine to produce more additional heat than the melting ice cubes would absorb. Bit like running a battery charger from the inverter!

 

 

Richard

[bizzard]

No, you are forgetting basic physics, the ice cube maker has to be powered by the engine alternator, so the increased power drain would cause the engine to produce more additional heat than the melting ice cubes would absorb. Bit like running a battery charger from the inverter!

Generator.

[alan_fincher]

Baffles or no baffles, the fact is that this engine appears correctly "plumbed" but Mike says the bottom of the skin tank is hotter than the top.

 

Unless the explanation of the top actually containing at least some air, rather than all water, holds good, that makes no sense at all to me.

 

Can anybody think of any other way this can possibly be the case, because we seem to be going around all kind of possibilities, but ignoring this one piece of information from Mike that seems just plain wrong!

 

Is the fan belt crossed over so water pump is running backwards ?!? - Only joking of course but if water is passing through the engine in the correct direction, how could we possibly be seeing "upside down" temperatures on the skin tank ???

[bizzard]

No, you are forgetting basic physics, the ice cube maker has to be powered by the engine alternator, so the increased power drain would cause the engine to produce more additional heat than the melting ice cubes would absorb. Bit like running a battery charger from the inverter!

Or if Mike only uses his boat in big hail storms,a big wide funnel placed in the filler could collect the ice stones and as they gently melt would drop through into the filler at intervals. That comforting Plop!Plop! letting him know that his engine is being sufficiently cooled.

[Albion]

Fair enough, and your argument is valid.

 

My "Evans and Son" (effectively "Mike Heywood") not only had an appallingly undersized tank, it also proved to have no baffles.

 

I'd have thougt LB were cleverer than that by the time Mikes was built, but of course it's possible even this has none.

The SWD wide beam that I used to own had a 75hp Beta and, at first glance, the skin tank looked a very adequate size. However on mine, and others who later cut open the skin tank and proved it, there were no baffles. Funnily enough mine used to accumulate air in the top of the tank also, despite always keeping the coolant well topped up etc and I never found out why before I sold it. It became a routine operation for me to keep releasing the air every few weeks to ensure best cooling (the engine had only about 200 hours on it so there was no chance of a head gasket problem and in any case, with my automotive background I would have soon spotted that type of problem). It was perfectly OK at canal speeds but, after sustained higher load cruising, would overheat. This direct experience with no baffles and accumulating air are why I am strongly suggesting that the skin tank be checked for air and baffles before getting into all the more esoteric solutions.

Roger

[Chalky]

I know it means draining some of the coolant, but could you check for baffles using a coat hanger to feel for them through one of the pipe accesses / bleed point?

[Rebotco]

I know it means draining some of the coolant, but could you check for baffles using a coat hanger to feel for them through one of the pipe accesses / bleed point?

 

Or get one of these for under £70 Inspection camera

[smileypete]

Or get one of these for under £70 Inspection camera

Great idea, but if a laptop is around a waterproof USB camera for £10 will do.

 

http://www.ebay.co.uk/itm/280776543718

 

cheers, Pete.

smpt

Edited May 29, 2012 by smileypete