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gedboyc
gedboyc

Posted: Tue Jul 14, 2015 10:19am

Post Subject: Engine Overheating

Hello i have a 57 NB and a vetus 43hp engine. Over 1800 revs the red alarm sounds off as over heating but gauge not in white danger area. have checked water levels and no air in skin tanks so think it may need water fushing out to clean. engine only done 1500 hours and 9 years old. How do you flush out the engine. Thanks any advice would help. gerry

Tony-B
Tony-B

Posted: Tue Jul 14, 2015 10:34am

Post Subject: Engine Overheating

I need more information. When did this start? What type of waterway? Is your prop clear of rubbish? What is the surface area of one side of the skin tank(s)? What, if anything, was done or happened before this occurred (assuming it has not been like this from new?) As you say skin tanks I assume this is a dry exhaust boat. I know Vetus do fit raw water failure alarms to the exhaust mixing elbow and if this is not disconnected on a dry exhaust boat it will sound a warning so please email a photo of your engine to Tony@tb-training.co.uk so I can see if this is still in place on your engine. At the same time tell me a bit about how long you have had the boat. At this stage I would say it is very unlikely that flushing the cooling system will do any good at all. If you have recently run out of coolant or drained the system it is far more likely to be an airlock somewhere. If you had a bad overheat for some reason it could also be a failed thermostat.

Tony-B
Tony-B

Posted: Tue Jul 14, 2015 2:10pm

Post Subject: Engine Overheating

You asked how to flush the cooling system. This assumes a proper keel/tank cooled engine. If you have a heat exchanger cooled engine bodged onto the skin tank the following will not work. Although you can flush without it I would buy some cooling system cleaner form the likes of Halfords or your local motor factor and follow the instructions on the container. It is often very difficult to get at the lower hose connection on the skin tank so take that hose of at the engine end and drop it into the bilge. Make sure the engine drip try is clean and take the drain plug out of the engine block. Pump or sponge the old coolant from the bilge and engine drip tray into containers for disposal at you local council waste site. This is classed as hazardous waste because of the antifreeze. Take the engine thermostat out and replace the thermostat housing. Put a hose from the mains water supply or from a pump into the the end of the hose you have just taken off and do your best to seal the joint in some way - Duct tape possibly. Turn the hose on. You will now have water flowing backwards through the system. You may like to hit the skin tank with a rubber mallet or shoe heel to help loosed any deposits. When water is running clear from the engine block drain replace the drain plug. Any water in the drip tray or bilge can be pumped overboard. Once the water is running clear out of the engine reverse the procedure. That is seal the hose into the engine and let the water flow out of the hose you will then have in the bilge.You can reverse it as many times as you wish. When the water runs clear replace the hose and replace the the thermostat. Now refill the system pint of water - pint of antifreeze to give you a roughly 50% mixture. Bleed the system topping up as required with a 50% antifreeze mixture. Run up to temperature with the filler cap off so any air trapped in pipes can escape. Re-bleed the skin tank. As I said I very much doubt this will solve the problem.

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