Yacht Wiring Diagram
Servicing a Yacht’s Cooling System
The bulk of yachts with inboard engines are built with fresh-water cooling systems. The fresh water systems are designed to function with the raw water systems to cool the engines while running. Fresh water circulates within the engine block and transfers the heat to the raw water when is passes through heat exchangers. This article will explain the step by step approach to servicing your yacht’s raw water cooling system.
Over time, the raw water system on a boat will become clogged with calcium carbonate, usually called scale. This scale will create troubles for your engines. Heat exchangers will become clogged and may become totally blocked.
So how does this occur you ask? When sea water contacts heated surfaces, minerals fall from suspension. Those minerals, mainly calcium, attach itself to metal surfaces inside heated parts on the boat. The same thing happens inside hot water heaters.
Become knowledgeable with your engines
Prior to servicing the engines on your used trawler, motor yacht, sailboat or cruiser, it is important that you take some time to familiarize yourself with the raw water cooling system of the engines. Get drawings and parts diagrams if at all possible. Study your engines and trace the raw water flow from the intakes to the discharge. Make a mental note of each component.
There are two methods to overhaul your used boats engine.
Method 1 – Disassemble the Engine Cooling System
With your part’s manual close at hand, take apart each portion of the raw water system. You are going to need new seal and gaskets when you reassemble so keep a count of what you will need as you take things apart. Each engine is different but you will have a raw water pump and impeller, a primary heat exchanger and likely transmission and oil coolers .
Clean the system
When the components have been disassembled, each part must be carefully examined. Coolers and exchangers will likely have scale built up within them. A commercial radiator shop can clean the exchangers for you but you can do it yourself by using a 4 to 1 mixture of Muriatic Acid and fresh water. Lower each part into the acid solution and allow to “boil”. When all activity is done, you parts will be clean of scale. Be careful; wear eye protection to protect your eyes.
Put your system back together.
When your parts are clean, its time to put everything back together using new seal and gaskets where necessary. And you if find rusted bolts and nuts, it is a good thought to replace those too. Now is a good time to replace the impeller too.
Operate the engine and check for leaks; repair as needed
When you are refilling your engine with anti-freeze, be sure to bleed the system of trapped air. The method to use will be in your owner’s manual. Following the re-assembly, the only thing left to do is start the engine and check for leaks.
Method 2 – Clean in Place with a Closed Loop
Inspect your cooling system and locate your raw water pump on your used boat. Locate the “intake” for the raw water system downstream from the raw water pump; here is where you will want to connect a supply hose. On my diesel engines, I have a hose that runs from the water pump to the oil cooler that I can temporarily remove. Then locate an outflow from the raw water cooling system where the water leaves the engine.
Gather the following:
1. – 50 gph bilge pump
2. – About 20 feet of wire to plug in the pump to your batteries
3. – A 5-gallon bucket
4. – About 10-15 feet of hose sized to fit connectors
5. – 1 gal of Ph-Ospho-Ric (Hardware Store paint department) phosphoric acid
Connect a piece of the hose to the bilge pump and the other end to the “intake” you found.
Place the bilge pump into the bucket and fill ½ full with water and ½ of the Ph-Ospho-Ric. Connect another portion of hose to the outflow of the engine and route back to the bucket. You’ll want to remove the engine zincs and plug the holes. New engine zincs should be installed when complete.
What you now have is a “closed loop” where acid can be circulated through the engine. Start the bilge pump and begin circulating the water and acid. The water will turn a dark gray and bubble as it liquidates the calcium deposits. You may have to add more Ph-Ospho-Ric as you continue the process.
When the cleaning is complete and you are sure the scale has been removed, reassemble the engine, put in new engine zincs, and start the engine to flush the remaining acid. You are all
About the Author
Mike Dickens, the author, is a boat owner and owner/Broker of Paradise Yachts.
Paradise Yachts is a Yacht Brokerage offering used yachts to customers worldwide.
Visit our website to view our selection of Used Trawlers, Used Motor Yachts, and Used Sailboats .
National and international sales. We ship Used Yachts and Used Boats worldwide. Located in Florida, USA. 904/556-9431
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