Keel Cooler Sealing Advice

[cal_d_44]

Hi all, I am after some advice I have a Nanni 55 hp engine that is designed for keel cooling, the manufacture recommends 1.85 sqr/mtr of surface area for effective cooling at >18 deg C water temp, and as I will be sailing mainly in the tropics. I have built one side, and together it will have about 1.95 sqr/mtrs of surface area and hold around 20 ltrs of coolant total (inc engine). I have built one side and have pressure tested it to 20psi the overflow/heat expansion cap is pressure rated to 1bar/14.5 psi, now in over an hour it lost 0.5psi through two small pinprick holes that I can not get too to weld them effectively. Any advice on how I could seal them. Was thinking of filling it with a thinned oil base paint pressurising it and then draining and washing the paint out??? each cooler side hold around 4 ltrs. Any advice would be appreciated.
Cheers
Cal

[HappyMdRSailor]

Wow...

Keel cooled ... Outside the boat heat exchanger for a diesel is a new one on me...

I don't think any type of coating on the interior of the cooler is going to work... We're talking hot AND pressure... Plus... coatings will diminish the heat transfer ability... I've got nothing but proper braze/solder/weld suggestions...

[cal_d_44]

Cheers HappyMdRSailor

[HappyMdRSailor]

Originally Posted by cal_d_44

Cheers HappyMdRSailor

Cheers back at ya Cal...

Snap a picture if it's not too inconvenient... Curious to be sure...

[Snowpetrel]

What about any of the automotive radiator leak fixers? Good system having keel cooling. I had keel cooling in snowpetrel. The skeg was the cooling tank. How is your exhaust designed?

[cal_d_44]

Will do HappyMdRSailor,

Hi Snowpetrel, thought about them however they say they are a temporary fix on the bottle? Not sure if I would loose coolant because I doubt it will get to 1 bar too often could be wrong though, every one I have spoken to with a KC says they get warm to the touch but not hot?? how was yours?

The exhaust I plan on making from stainless steel exhaust pipe covered in Exhaust wrap and then a layer of Aerogel Pyrogel. The exhaust will go through a SS muffler loop up and exit the boat at water level. Would like to hear your experiences?

Cheers

Cal

[Zach]

Can you get a small diameter stick welding rod, bend the rod up into a knot and get a weld on it that way?

Zach

[Snowpetrel]

Originally Posted by cal_d_44

....every one I have spoken to with a KC says they get warm to the touch but not hot?? how was yours?

Never did actually find out just how hot it got. there was never any sign of any significant heat.

Originally Posted by cal_d_44

The exhaust I plan on making from stainless steel exhaust pipe covered in Exhaust wrap and then a layer of Aerogel Pyrogel. The exhaust will go through a SS muffler loop up and exit the boat at water level. Would like to hear your experiences?

Snowpetrels was exhaust tubing, about 40mm and thin wall, with expanded joints and an automotive muffler. It was quiet enough but I often had problems with slight leakages smelling and vibration. I used fibreglass insulation, which made it much safer, but was rather nasty. I like the sound of the pyrogel stuff. heat and fire risk needs to be taken seriously.

The biggest problem for me was the flexible joint, it would only last a few years before getting pinholes. carry a spare and carefully align them with in spec. Better to flange them so you can easily swap them out. Ideally the whole exhaust would be sleeved with a vent from the engine room and a fan to create negative pressure and remove engine and exhaust smells.

A friends boat used heavy wall galvanised pipe with no joins, except the flexible coupling. He ran it through a separate insulated trunk under his bunk aft, and had the end pivoted so he could put it underwater to muffle it. This system never seemed to give any problems. But was very loud without a muffler, though when underwater it was OK.

Another mate had a vertical stack like a trawler, just under his boom. It worked great, all built from heavy stainless steel, including the muffler, but when motorsailing to windward it would stink out the cockpit. He had a drain at the bottom of the muffler. Allowance needs to be made for expansion as well as vibration.

I would love to find a way to cool the exhaust using the engine cooling water. I was thinking of wrapping the cooling water pipe around the exhaust, with a layer of insulation between to stop direct contact.

Be careful of water cooling jackets that are above the engine, as any leaks into the exhaust could flow back into the cylinders and hydraulic the engine as happened to me on a square rigger once.

At the moment I am installing a conventional system in the new boat, but would love to go back to keel cooling at some point. I loved the simplicity of the keel cooler and dry exhaust.

Cheers