Raw Water Intake

[RobinJ]

In order to alleviate some overheating problems, particularly on long cruising, I installed a raw water secondary cooling system, mounting the intake on the counter (port side), so is only a few inches below the surface. It gives the flexibility to use skin tank cooling, raw water or both, depending on conditions.

 

It has worked well, but does collect a fair bit of floating detritus in the filter (leaves etc.).

On a recent river trip however, I was passed by a large trip boat at speed, resulting in cavitation and loss of raw water (air up the intake), apart from any initail worry, the air was eventually pumped through.

 

Question is where is the intake on everybody elses raw water located?

Do those fitted through the bottom cause more problems on shallow waters?

I could fit the intake on the swim (but would have to be on the starboard side), what is the best compromise?

[blackrose]

In order to alleviate some overheating problems, particularly on long cruising, I installed a raw water secondary cooling system, mounting the intake on the counter (port side), so is only a few inches below the surface. It gives the flexibility to use skin tank cooling, raw water or both, depending on conditions.

 

It has worked well, but does collect a fair bit of floating detritus in the filter (leaves etc.).

On a recent river trip however, I was passed by a large trip boat at speed, resulting in cavitation and loss of raw water (air up the intake), apart from any initail worry, the air was eventually pumped through.

 

Question is where is the intake on everybody elses raw water located?

Do those fitted through the bottom cause more problems on shallow waters?

I could fit the intake on the swim (but would have to be on the starboard side), what is the best compromise?

 

A second skin tank. (sorry)

[Albion]

In order to alleviate some overheating problems, particularly on long cruising, I installed a raw water secondary cooling system, mounting the intake on the counter (port side), so is only a few inches below the surface. It gives the flexibility to use skin tank cooling, raw water or both, depending on conditions.

 

It has worked well, but does collect a fair bit of floating detritus in the filter (leaves etc.).

On a recent river trip however, I was passed by a large trip boat at speed, resulting in cavitation and loss of raw water (air up the intake), apart from any initail worry, the air was eventually pumped through.

 

Question is where is the intake on everybody elses raw water located?

Do those fitted through the bottom cause more problems on shallow waters?

I could fit the intake on the swim (but would have to be on the starboard side), what is the best compromise?

 

 

Can I add a supplementary question to this as it seems apposite. Does anyone know what the correct design of a mud box should be or any source of such on the web?

Roger

[blackrose]

Seriously though, why would you opt for raw water cooling if it's possible to install an auxillary skin tank?

 

I'm sure that closed loop systems suffer none of the drawbacks of raw water cooling: no hull penetrations below the waterline, no clogging with weeds and no mud boxes or filters to clean.

 

The majority of Dutch barges seem to have raw water cooling, so purely in terms of cooling the engine is it much more efficient?

Edited May 18, 2009 by blackrose

[Albion]

Seriously though, why would you opt for raw water cooling if it's possible to install an auxillary skin tank?

 

I'm sure that closed loop systems suffer none of the drawbacks of raw water cooling: no hull penetrations below the waterline, no clogging with weeds and no mud boxes or filters to clean.

 

The majority of Dutch barges seem to have raw water cooling, so purely in terms of cooling the engine is it much more efficient?

 

As I understand it the engine sizes on Dutch Barges are much greater (90 hp and upwards to huge) as opposed to a typical nb at 45 ish. This makes the fitting of a suitably sized skin tank that much more difficult due to the area involved. Can't remember for sure but there is some correlation between the engine hp and the skin tank area in sq ft (something like 1sq ft for every 5 hp IIRC). This calculation is only valid if the builder has bafffled the skin tank correctly also.

Roger

[Guest]

My last boat was raw watercooled. The intake was way down the swim so about 20 inches below the surface. It blocked once in Blackburn when it pulled in a plastic bag. Other than that it was fine, and always kept the engine cool. I tend to think that a properly designed skin cooling system is better because:

 

No extra hole in boat, one less valve to close on leaving boat.

No crud pulled into cooling system.

Antifreeze present to reduce corrosion.

Less trouble to winterise

 

On the other hand a poorly designed skin cooling system is useless.

 

That said if I fell in love with a boat, I would buy it regardless of which cooling system was employed (air included).

[RobinJ]

A second skin tank. (sorry)

No, thats a serious option (albeit future)

 

Seriously though, why would you opt for raw water cooling if it's possible to install an auxillary skin tank?

 

I'm sure that closed loop systems suffer none of the drawbacks of raw water cooling: no hull penetrations below the waterline, no clogging with weeds and no mud boxes or filters to clean.

 

The majority of Dutch barges seem to have raw water cooling, so purely in terms of cooling the engine is it much more efficient?

It was a simple and quick fix as opposed to removing engine (and boat), dismantling existing skin tank to fit baffles and or addiitonal tank (which may still have to be done).

No opting for raw water, simply the benefit (short term at least) of both!

[Naughty Cal]

Our water inlet is way down on the bottom of the hull. Think it is somewhere in the region of 2'4" down give or take an inch or so.

 

Just to add we never bother closing any of the valves on any of our skin fittings (except the toilet) when we leave the boat. It never leaks a drop and there is no problem forgetting to reopen them.

 

Dont know if its more efficient than skin cooling but it certainly keeps our lump cool. I reckon you would struggle to fit a skin tank big enough on ours

[FadeToScarlet]

Our water inlet is way down on the bottom of the hull. Think it is somewhere in the region of 2'4" down give or take an inch or so.

 

Just to add we never bother closing any of the valves on any of our skin fittings (except the toilet) when we leave the boat. It never leaks a drop and there is no problem forgetting to reopen them.

 

Dont know if its more efficient than skin cooling but it certainly keeps our lump cool. I reckon you would struggle to fit a skin tank big enough on ours

 

I'm not sure if you could fit a skin tank anyway. I was looking into moulding one in GRP to go in the boat, but it would get too hot; it needs to be able to withstand the incoming very hot water from the engine.

 

I've got raw water cooling and it is one of the two banes of the boat. The inlet is too small and gets easily blocked, although it really does efficiently cool the engine; I can run all day at 1,800 RPM (5-800 more than canal speeds!) and yet not overheat- unless it sucks something into the intake.

 

The intake is on the swim on the port side, and it's very hard to get at it from the outside. It's about a third of the way up the swim, from the baseplate.

[Naughty Cal]

I'm not sure if you could fit a skin tank anyway. I was looking into moulding one in GRP to go in the boat, but it would get too hot; it needs to be able to withstand the incoming very hot water from the engine.

 

I've got raw water cooling and it is one of the two banes of the boat. The inlet is too small and gets easily blocked, although it really does efficiently cool the engine; I can run all day at 1,800 RPM (5-800 more than canal speeds!) and yet not overheat- unless it sucks something into the intake.

 

The intake is on the swim on the port side, and it's very hard to get at it from the outside. It's about a third of the way up the swim, from the baseplate.

 

Other than the plastic bag we have had no problems with water intake and it takes a lot of water to cool the lump at 3600-3800rpm!!!!!!

[Guest User]

Other than the plastic bag we have had no problems with water intake and it takes a lot of water to cool the lump at 3600-3800rpm!!!!!!

I thought you were supposed to take the wrapper off your boat before you used it ?

[Naughty Cal]

I thought you were supposed to take the wrapper off your boat before you used it ?

 

 

No it was of the Tesco variety

[alan_fincher]

 

No it was of the Tesco variety

Yes, and ?.............

[Naughty Cal]

Yes, and ?.............

 

Suppose its preferable to the Netto variety