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