Post Number: 2
|Posted on Saturday, October 16, 2004 - 04:58 am: ||
Can someone help with the best maintenance procedure for the cooling system on a Stuart R3M?
The engine is installed in a restored open clinker 20 footer with a stuart water intake skin fitting. This fitting also has a valve to allow cooling water to pumped from the bilge.
After using the boat in salt water I run fresh water through the engine from a bucket using the bilge hose. When the fresh water is emptied I allow the engine to run on until the system is dry.
Is this the best way to reduce rust in the engines cooling system or is it better to leave fresh water in the engine if possible?
I use the boat about once a week although occasionally it might sit for two or three weeks. It is stored on a trailer in a shed when not in use.
Post Number: 118
|Posted on Saturday, October 16, 2004 - 06:38 am: ||
Refer to the Technical Section of this website for a paper on Corrosion in Salt Water by Mark Stretch.
The rust created in the presence of salt water is a lot more coarse compared with fresh water and much more prone to creating blockages when it breaks loose and will lead to cracks in your water jacket when it expands in the narrow passages.
Also, the chlorides that are found in salt water are absorbed into the cast iron and then get drawn out as the cast irons dries (if you pump it dry) and again causes a severe rust scale.
Leave the fresh water sitting in the engine. It keeps the air away from the cast iron and the rust scale created in the presence of the fresh water is much finer than with salt water.
PS: You could use a heat exchanger - can be designed a number of different ways.
Post Number: 3
|Posted on Saturday, October 16, 2004 - 07:11 am: ||
Tim, thanks for your suggestions.
At this stage I'm not sure about placing heat exchanger gear under the hull. My feeling is it will be too easily damaged, especially during launching and retrieval, but I may change my mind after seeing what's available.
Meanwhile I will keep the fresh water in there as you suggest and check out the article written by Mark.
Post Number: 312
|Posted on Saturday, October 16, 2004 - 08:56 pm: ||
A very sucessful, cheap heat exchanger that will handle a lot of relativly rough handling consists of a 3/4" copper pipe along side the keel rubbing strip. Starting out near the stern go up near the bow make a U turn and come back toward the stern on the other side of the rubbing strip. Make up a small vertical exspansion tank out of approx 2 inch dia. copper pipe. Go from the exspansion tank to the the pump. Pump outlet to cylinder inlet. Cylinder outlet to the heat exchanger pipe along the keel. Return is piped to the the exspansion tank. This completes the circuit. Make sure the filler cap on the exspansion tank has a vent hole. Run 50:50 fresh water and automotive anti freeze in the closed system. Leave the 50:50 mixture in the system year round and you won't have to worry about salt exspansion cracking the water jacket and your engine can run much hotter. If you run salt water in the jacket and the temp is allowed to go over 143F, salt will percipitate out and clog the jackets badly
Post Number: 4
|Posted on Saturday, October 16, 2004 - 10:51 pm: ||
Thanks Richard I wasn't aware of the temp issues relating salt water cooling. It seems like I will have to embrace the heat exchanger system as it is obviously the best solution for keeping the engine in good condition. Your system sounds very good.