80 degree thermostat on JP2

[mykaskin]

Hi Folks,

 

Thanks to the breakage of my 60 degree thermostat, and the difficulty of getting a new one has meant an 80 degree one had to be fitted to keep me going.

 

So far, apart from the engine running much hotter, it doesn't seem to have been any problem, but I've only gone from Braunston to Alvecote.

 

Any thoughts on if I might have future problems?... especially when I'm running hard loaded or on rivers? What about salt water, I understand the manual suggests running at 55 degrees for salt water, but since I'm only occasionally on salt water will it be an issue - furring up?

 

Cheers,

 

Mike

[sebrof]

My JP3 manual says that the engine should be run as close to 77 degrees as possible when not using a radiator (I have keel cooling). Can't see why a JP2 should be different but I am no expert.

[steamraiser2]

Its a little on the hot side but not too much, a 75 degree would be better

[David Mack]

Hi Folks,

 

Thanks to the breakage of my 60 degree thermostat, and the difficulty of getting a new one has meant an 80 degree one had to be fitted to keep me going.

 

So far, apart from the engine running much hotter, it doesn't seem to have been any problem, but I've only gone from Braunston to Alvecote.

 

Any thoughts on if I might have future problems?... especially when I'm running hard loaded or on rivers? What about salt water, I understand the manual suggests running at 55 degrees for salt water, but since I'm only occasionally on salt water will it be an issue - furring up?

 

Cheers,

 

Mike

 

Fulbourne's National has no thermostat, and normally runs pretty cool. I've never measured the temperature, but putting a hand under the outlet I would describe it as no more than 'warm'.

 

David

[mykaskin]

When running raw water it was hard to keep the correct temp. I'm not sure about your setup on the National, but there is a valve on the JP which limits the amount of water running through the engine - the rest bypassing, and going straight over board. The outlet was always cold because most of the water was bypassing the engine.

 

Different engines are designed to run at different heat - the Kelvin K's for example run very cold - but still have a clean exhuast... work that one out.

 

The combustion was poorer when I didn't get the setting right, and it seems to run much more happier (cleaner) with the thermostat.

 

I guess I'll see how it goes, and make sure I have a spare one aboard this time.

 

Cheers,

 

Mike

[flatplane8]

When running raw water it was hard to keep the correct temp. I'm not sure about your setup on the National, but there is a valve on the JP which limits the amount of water running through the engine - the rest bypassing, and going straight over board. The outlet was always cold because most of the water was bypassing the engine.

 

Different engines are designed to run at different heat - the Kelvin K's for example run very cold - but still have a clean exhuast... work that one out.

 

The combustion was poorer when I didn't get the setting right, and it seems to run much more happier (cleaner) with the thermostat.

 

I guess I'll see how it goes, and make sure I have a spare one aboard this time.

 

Cheers,

 

Mike

 

Hi, I think you may have covered this before, but was it hard to adapt the raw water cooling to thermostat?

[Proper Job]

IIRC the thermostat in my JP3 is (oddly enough) 76 deg. + or - 5 degrees I'd have thought would be acceptable.

 

Don't forget that JP's are prone to cracking cylinder heads if they overheat

 

But they do like to run hot (in comparison to many engines of their era)

[Timleech]

IIRC the thermostat in my JP3 is (oddly enough) 76 deg. + or - 5 degrees I'd have thought would be acceptable.

 

Don't forget that JP's are prone to cracking cylinder heads if they overheat

 

But they do like to run hot (in comparison to many engines of their era)

 

I think the cracking is more likely from serious overheating (running out of water) probably often combined with sudden cooling from reinstatement of the water.

 

Tim

[David Mack]

When running raw water it was hard to keep the correct temp. I'm not sure about your setup on the National, but there is a valve on the JP which limits the amount of water running through the engine - the rest bypassing, and going straight over board. The outlet was always cold because most of the water was bypassing the engine.

 

Fulbourne's is just a single pass straight through: seacock - mudbox - water pump - engine - outlet pipe. No means of controlling the water flow, except I suppose by partially closing the seacock (or allowing the mudbox filter to clog).

 

David

[martyn 1]

The below text is taken directly from the Lister technical information for the installation of JP,JS and JK marine propulsion and auxilary engines.

 

Which in short says. raw water cooled(Salt) do not exceed 55 °C. Fresh water sealed system upto a max of 82°C

 

Hope this help.

 

Enclosed Fresh Water Cooling.

 

For vessels operating in sandy or polluted water or where corrosion is prevalent, it is advisable

to employ a closed circuit fresh water cooling system. ".

When this is employed higher water temperature may be allowed to 180°F. (82°c.) with a

consequential increase in efficiency.

 

Temperature Control.

 

It is important to remember that the engine is a HEAT engine and should be kept hot whilst

running.

The circulating water temperature can be regulated by means of the control cock on the

exhaust manifold (for JP2,3M & MA engines) which allows a proportion of the water pump output

to bypass the engine jackets. A temperature control valve for JS3MA engines is fitted on

the water discharge manifold. Normal working temperatures should not exceed 130°F. (55 °C.) or

be less than l20°F. (50oC.) running continuously for long periods when sea water cooled. or

180°F. (82°C.) maximum, 140°F. (60°C.) minimum under the same conditions when freshwater

cooling is employed.

[sebrof]

I really can't understand the enormous temperature differential between sealed and raw cooling systems.

[by'eck]

I really can't understand the enormous temperature differential between sealed and raw cooling systems.

 

I think this is out of necessity rather than an ideal situation. Not sure if it was to reduce corrosion, silt build up at base of liners or other reason.

 

Whatever Lister later introduced fresh water cooling for JPM's with dedicated pump working through heat exchanger, itself cooled by sea water as in modern indirectly cooled marine engines.

[Proper Job]

I really can't understand the enormous temperature differential between sealed and raw cooling systems.

It's all about calcium deposits and potential blocking of waterways. The higher the temperature, the more the calcium (and other bits) are forced out of solution and stick to the hot metal surfaces (internal waterways of the engine).

 

With a closed loop system, you have a limit on the amount of dissolved solids in the water and can run them at a higher temperature. With open systems, you run them at a lower temperature to minimise the amount (endless supply of dissolved solids as the water is constantly renewed) of deposits.

 

Think about your kettle.

[by'eck]

It's all about calcium deposits and potential blocking of waterways. The higher the temperature, the more the calcium (and other bits) are forced out of solution and stick to the hot metal surfaces (internal waterways of the engine).

 

You took the words out of my mouth

 

See here how years of passage of sea water have formed a plug in water passage to head on this JP2M.

 

[Proper Job]

And the same thing will happen in the primary/secondary heat exchanger on indirect raw water cooled engines.

 

I've spent many a happy hour drilling out cooling tubes

 

That's why skin cooling is so popular

[Timleech]

And the same thing will happen in the primary/secondary heat exchanger on indirect raw water cooled engines.

 

I've spent many a happy hour drilling out cooling tubes

 

That's why skin cooling is so popular

 

They should just need rodding though once a year. A good exchanger will be designed to facilitate that

Cylinder blocks aren't, also the cylinders will potentially get much hotter than the water passing around the tubes.

Also good exchangers will have tubes of Monel or something similar, which seems to discourage buildup of crud.

 

Tim

[by'eck]

Reminds me of a brilliant US product called On and Off. Not sure if its available over here but its sold as a fibreglass hull cleaner. It seems to consist of a cocktail of acids of various dilutions including muriatic, phosphoric & hydrochloric!

 

Like it says on the packet you just apply to rust patch on almost any surface then wash off - rust stain gone.

 

Used with a syringe it works wonders on heat exchanger tubes, in smaller engines at least.

[Timleech]

Reminds me of a brilliant US product called On and Off. Not sure if its available over here but its sold as a fibreglass hull cleaner. It seems to consist of a cocktail of acids of various dilutions including muriatic, phosphoric & hydrochloric!

 

Like it says on the packet you just apply to rust patch on almost any surface then wash off - rust stain gone.

 

Used with a syringe it works wonders on heat exchanger tubes, in smaller engines at least.

 

 

ermm, muriatic is hydrochloric

 

Tim

[Proper Job]

They should just need rodding though once a year. A good exchanger will be designed to facilitate that

Cylinder blocks aren't, also the cylinders will potentially get much hotter than the water passing around the tubes.

Also good exchangers will have tubes of Monel or something similar, which seems to discourage buildup of crud.

 

Tim

Big engines (circa 20,000 hp) had big heat exchangers

[mykaskin]

And the same thing will happen in the primary/secondary heat exchanger on indirect raw water cooled engines.

 

I've spent many a happy hour drilling out cooling tubes

 

That's why skin cooling is so popular

 

I was thinking about a dual system - perhaps with some keel cooling as well for when the mudbox gets blocked. It seems there isn't an ideal solution without having loads of plumbing and extra things to go wrong though!

 

I think at least I'll find a lower temp thermostat as I don't fancy furring up my engine.

 

Cheers,

 

Mike

[RLWP]

I was thinking about a dual system - perhaps with some keel cooling as well for when the mudbox gets blocked. It seems there isn't an ideal solution without having loads of plumbing and extra things to go wrong though!

 

I think at least I'll find a lower temp thermostat as I don't fancy furring up my engine.

 

Cheers,

 

Mike

 

Isn't that odd. I've always considered my skin tank system to be very simple and to have less things to go wrong than a raw water system

 

Richard

[mykaskin]

Isn't that odd. I've always considered my skin tank system to be very simple and to have less things to go wrong than a raw water system

 

Richard

 

The recipical pump on the engine would not be suitable for a closed system, so I'd need another pump. It would also need a header tank, and a retrofitted skintank on a boat which doesn't have a straight line in sight!

 

Mike

[Timleech]

The recipical pump on the engine would not be suitable for a closed system, so I'd need another pump. It would also need a header tank, and a retrofitted skintank on a boat which doesn't have a straight line in sight!

 

Mike

 

The reciprocating pump might not be ideal for the job, but -

I installed a JP2 many moons ago with a sort of 'hot well'/skin tank, it's always worked very well AFAIAA.

Basically a large volume, unsealed skin tank welded into the chine of the boat. It does need a lot of antifreeze, and the pump needs to be reasonably 'tight' not to loose significant volumes of coolant, but yes it can be done successfully.

 

Tim

[RLWP]

The recipical pump on the engine would not be suitable for a closed system, so I'd need another pump. It would also need a header tank, and a retrofitted skintank on a boat which doesn't have a straight line in sight!

 

Mike

 

Is that because the piston of the pump is moving in and out of the closed system? I suppose if it was a vented system it would work OK

 

Anyway, it's hypothetical as I don't have a reciprocating pump, and I'm not jealous, no not at all...

 

Richard

[sebrof]

It's all about calcium deposits and potential blocking of waterways. The higher the temperature, the more the calcium (and other bits) are forced out of solution and stick to the hot metal surfaces (internal waterways of the engine).

 

With a closed loop system, you have a limit on the amount of dissolved solids in the water and can run them at a higher temperature. With open systems, you run them at a lower temperature to minimise the amount (endless supply of dissolved solids as the water is constantly renewed) of deposits.

 

Think about your kettle.

 

Makes sense. Thank you - and all others who also responded.