JP2 Overheating

[Tiggers]

I have a closed system JP2, and I really don't think the cooling is sufficient.

 

There are 2 skin tanks, both of which are tiny. To try and add a bit of capacity, they have run pipes down the length of the backcabin, but this do not seemed to have worked, and she is still running VERY hot at not very high revs.

 

Now I have not got any more room to expand the skin tanks, or add any more, and I do not want her being raw water cooled, so wondered if anyone had any other ideas?

 

It has been recommended that I weld some pipes on the swim on the outside which seems to be the best idea so far, but I really have no idea how much this is going to cost - anyone have any clue?

 

A good friend has quoted me for the work, but I doubt they are going to get time.

 

I promise this is the last problem with my engine! It was all so simple with the air cooled HA!

[RLWP]

Could you post some pictures of the skin tanks and installation?

 

Richard

[Chris Pink]

Why not go for raw water cooled? With or without heat exchanger it was how they were designed to run.

 

I speak as someone who ran a raw water engine for 10 years, it very rarely gave trouble.

 

 

 

Or perhaps fit a calorifier? (this time of year I can think of lots of ways to use any spare heat)

[MoominPapa]

It has been recommended that I weld some pipes on the swim on the outside which seems to be the best idea so far, but I really have no idea how much this is going to cost - anyone have any clue?

FadeToScarlet and BlackIbis did this to convert a raw-water cooled engine to closed system, so it might be worth dropping one of them a PM asking for costs.

 

MP.

[The Bagdad Boatman (waits)]

Can you squeeze in some central heating radiators? If a skin tank has not got baffles fitted then the water takes the shortest route from the inlet to the outlet. Are the skin tanks getting hot? hat is caused by ignition and friction, by running my FR on fully synthetic oil it ran much cooler.

[Guest Quo Vadis]

I have no experience of these things per se, but could a car heater assembly feature in this?

After all, they are a compact radiator with a powerful, variable speed fan, neatly packaged and readily available from scrapyards.

Could also be used to heat the boat.

[Timleech]

Skin tanks or pipes on the outside are probably your best bet if you don't want raw water cooling.

Radiators etc aren't a real answer, you won't always want that heat inside the boat.

 

If you're using an original JP ram pump, these don't shift a great amount of water. Closed circuit systems work much better with a higher water flow rate, so changing the pump to, for instance, a suitably rated Jabsco might bring a significant improvement although it sounds as though you're in need of a major improvement.

 

Tim

[Tiggers]

At work at the moment, but when I get home, I'll post some pictures. The skin tanks don't seem to get warm, but not sure if they have baffles in them.

 

I suppose I could fit a calorifier, it's just where I am going to put it, I like my engine room to look like an engine room (i.e. no calorifiers, alternators etc, just the engine and a tool box!). I am quite fortunate though, as my engine room is nearly 9' (only engine room I have seen that makes a JP look small) so there is plenty of room for modifications.

 

Don't really want to convert it to raw water, as it has been a closed system since it was put in the boat 34 years ago

 

Skin tanks or pipes on the outside are probably your best bet if you don't want raw water cooling.

Radiators etc aren't a real answer, you won't always want that heat inside the boat.

 

If you're using an original JP ram pump, these don't shift a great amount of water. Closed circuit systems work much better with a higher water flow rate, so changing the pump to, for instance, a suitably rated Jabsco might bring a significant improvement although it sounds as though you're in need of a major improvement.

 

Tim

 

Was the major pun intended?

 

It is the original JP pump, but once again, a bit begrudged at removing that.

[RLWP]

<snip>

 

Don't really want to convert it to raw water, as it has been a closed system since it was put in the boat 34 years ago

 

If it has been there for thirty four years, why is it running hot now?

 

Before converting to raw water/fitting cooling pipes/radiators/calorifiers/car heaters can we make sure the existing system is working as intended?

 

Richard

Edited December 13, 2011 by RLWP

[Chris Pink]

if the skin tanks don't get warm then your problem is not the capacity of the tanks.

 

It must be somewhere else.

 

Integrity of your pump or flow rate. You don't have to remove the existing pump, fit a jabasco inline (could even be an electric one) you could always disguise it -a bakelite radio perhaps?

 

it could be an internal blockage or limescale too.

[Tiggers]

If it has been there for thirty four years, why is it running hot now?

 

Before converting to raw water/fitting cooling pipes/radiators/calorifiers/car heaters can we make sure the existing system is working as intended?

 

Richard

 

The problem is, John (previous owner) never run her up past tick over! When I first took the boat out with him, we had just gone through Stoke locks, and were just above tick over, when he leaned in and said 'that's usually as fast as I go with her' Needless to say she was rather coked up when I took her (the exhaust note has now changed completely)

[alan_fincher]

How big actually are the skin tanks, and where exactly are they ?

 

As you say "tanks" not "tank" they must be two joined together, so are they in "series" or "parallel" ?

 

(Pictures say many words in cases like this).

 

If it has been that way for a huge number of years, then either it used to work, and something has changed to stop it working now, or it never worked well, which seems a bit unlikely.

 

Is the engine known to be in good condition ? Any chance it could have head gasket problems, or similar ?

 

If the JP2 is a nice one, and running well, I might consider a straight swap for a nice air-cooled HA3!

[Tiggers]

I will admit that I was completely nieve about JPs when I first got her, and it was actually Joe who raised his concerns about her overheating

 

 

If the JP2 is a nice one, and running well, I might consider a straight swap for a nice air-cooled HA3!

 

Not a chance Mr Fincher! Apart from the cooling, she is an amazing example of a JP (plus I dont like 3 cylinder engines!)

[alan_fincher]

Not a chance Mr Fincher! Apart from the cooling, she is an amazing example of a JP (plus I dont like 3 cylinder engines!)

Well it was a throw away remark, of course. The JP2 wouldn't be a "correct" engine for Sickle anyway, whereas the HA3 is actually spot on for part of her working careeer.

 

Alan

 

(Also prefers 2 cylinders!....)

[rjasmith]

I don't suppose it could be something simple like air in the skin tanks that needs bleeding out could it?

 

Richard

[Timleech]

At work at the moment, but when I get home, I'll post some pictures. The skin tanks don't seem to get warm, but not sure if they have baffles in them.

 

I suppose I could fit a calorifier, it's just where I am going to put it, I like my engine room to look like an engine room (i.e. no calorifiers, alternators etc, just the engine and a tool box!). I am quite fortunate though, as my engine room is nearly 9' (only engine room I have seen that makes a JP look small) so there is plenty of room for modifications.

 

Don't really want to convert it to raw water, as it has been a closed system since it was put in the boat 34 years ago

 

 

 

Was the major pun intended?

 

It is the original JP pump, but once again, a bit begrudged at removing that.

 

Maybe I'm being dense, but I can't see a pun - so no, definitely not intended!

 

If your tanks are not getting hot while the engine is, either you have something restricting the water flow or they are full of air.

 

Edit to add - if the first part of the first tank is hot but the rest is not, then you need to look at improving the flow.

I suppose you've checked that the pump really is pumping, ie no stuck valves?

 

OK, just spotted your boat name.

 

Tim

Edited December 13, 2011 by Timleech

[rjasmith]

Maybe I'm being dense, but I can't see a pun - so no, definitely not intended!

 

If your tanks are not getting hot while the engine is, either you have something restricting the water flow or they are full of air.

 

Tim

 

I think she thought you meant a "Canis Major" improvement perhaps!

 

Richard

[Tiggers]

Hmmm, I am going to have to double check if the skin tanks (one on each side) are getting hot or not. The pump is working well. I do regularly check for air in the tanks and engine, so I do not think it is that. I think pictures would help, I will post some tonight

Edited December 13, 2011 by Tiggers

[starman]

I was wondering about air locks too (a JP2 near us suffered from them) and whether in some way this issue was connected to the problem about disappearing coolant you raised a while back.

[alan_fincher]

OK, another way of looking at this, based on my own experience of Chalice's formerly undersized skin tank......

 

If your skin tanks are simply too small, or too inefficient for the engine you have, and the power at which you are using it, then the problem will manifest itself as the whole skin tank being hot the whole way down, and water being returned to the engine from the pipe at the bottom that is far hotter than it should be.

 

If you are in that situation, then because your engine is now being fed by water that is still hot, it is not able to take enough heat out of the engine, and the overheating starts.

 

A properly working skin tank will be hot at the top, with a temperature gradient down it, and should be pretty cool at the bottom. If your skin tanks have a good temperature gradient down them, and the pipe returning water to the engine is not very warm, then your skin tanks are doing a good enough job at the time, and are not undersized for the use you are trying to make of them.

 

If the tank isn't getting properly hot even at the top, (and maybe even the top hose isn't fully hot), then it is a problem with circulation, not the skin tanks. That can be pump not working properly, thermostat failed shut or part shut, air lock, or just enough crap somewhere in the system to stop the water flowing.

[steamraiser2]

The original JP water pump is entirely adequate for your boat. If you are not getting the skin tanks hot you may well have a blockage or an airlock. Only today we have been attempting to unblock the top water rail of a JP3M that was down to about a quarter inch of waterway! JPs also suffer from scale in the block and sometimes the wet exhaust box too.

 

I would suggest that you need to confirm that you have proper circulation throughout. Check that the balance pipe between the two skin tanks (you should have one) is clear as this a prime place for rust and silt to collect. If this is ok the wet manifold and wet silencer are also prone to scale and rust.If your engine still has manual cooling system valves check those too. The pump body, wet silencer , manifolds and block are likely to have drain valves which should run clear. If all these are proven clear and you can vent water from all the drain cocks but the engine still runs too hot I would fear that the block itself is choked up. It's not uncommon.

 

The JP3M we are currently restoring gave up a bucket full of rust, mud and scale but still ran cold, which is what caused it to prematurely wear out. JPs are heat engines and, uncommonly for a vintage engine can run happily up to the low 80s C.The hard part is normally trying to get them hot enough!

 

In your case I would guess that a lack of circulation is the issue.Please don't throw away your money with novelty fixes, check that you have plenty of water circulating first!

[Timleech]

The original JP water pump is entirely adequate for your boat. If you are not getting the skin tanks hot you may well have a blockage or an airlock. Only today we have been attempting to unblock the top water rail of a JP3M that was down to about a quarter inch of waterway! JPs also suffer from scale in the block and sometimes the wet exhaust box too.

 

 

 

In your case I would guess that a lack of circulation is the issue.Please don't throw away your money with novelty fixes, check that you have plenty of water circulating first!

 

 

I agree it's adequate *if* the skin tanks are adequate. What I was pointing out is that skin tanks work more effectively with a faster flow, & if they really are too small and there really is no way of making them bigger, a faster flow could help

That said, the JP pump when working properly does move water than do some other direct-cooled engine pumps.

 

Tim

[David Mack]

If the tank isn't getting properly hot even at the top, (and maybe even the top hose isn't fully hot), then it is a problem with circulation, not the skin tanks. That can be pump not working properly, thermostat failed shut or part shut, air lock, or just enough crap somewhere in the system to stop the water flowing.

 

Or a valve which should be open isn't.

 

Some years ago I had to sort out a friend's (house) central heating. Hot water just would not circulate around the radiators. The problem eventually turned out to be a gate valve where the spindle had become detached from the 'gate'. The valve handle turned normally a couple of turns in each direction, but on dismantling it was clear that the gate was remaining resolutely shut. A new valve solved the problem.

 

David

[Tiggers]

Thanks everyone so much for your help. I am going to take her out Thursday for a run and check to see if the skin tanks are getting hot and will report back!

[sebrof]

Thanks everyone so much for your help. I am going to take her out Thursday for a run and check to see if the skin tanks are getting hot and will report back!

 

Tiggers, it's really very simple.

 

If the water is returning hot from the skin tanks, then they are too small. Simple as that. It's not a pump problem, because if the pump were too slow, the water would have extra time to cool, and would therefore be cooler, not hotter. And if the pump is too fast, and the tanks adequate, the engine would not be getting too hot.

 

If the water is returning cool, and the engine is still too hot, then it COULD be a pump problem, in that the water may be being pumped around too slowly to remove all the heat. If that is the case, the water coming out of the engine will be very hot.

 

It could also be a thermostat problem, if the 'stat is not cutting in until the engine is too hot. Measure the temp of the water. Above around 75 degrees it should start to be diverted to the skin tanks.

 

It could also be a blockage/air-lock in the skin tanks. I had that problem with my JP3. Water was being diverted at the right temp by the stat, but the air-lock prevented much of it from getting through. So not enough was going through the skin tank, and the rest was being forced through the thermostat and back round the engine. Bad for pump, pipes and stat. In my case, the problem (an air-lock) cleared itself on a long run with the engine working hard.

 

Surprised you don't like JP3s. They are the smoothest and quietest of the JPs.