When remaking your main engine cooling system I suggest installing a water strainer just downstream of the raw water pump. Connect it so that the water enters between the transparent housing and the strainer so you can see any debris in collected the strainer.
This will catch impeller bits before they lodge in the heat exchanger or riser water injection nozzle. You will then be able to see when it is time to change the impeller and will not have to clean out rubber bits downstream. Doing this will save a great amount of work, thus greatly reducing the time required to recover from a blown impeller, a Good Thing especially if one is underway. (Trust me... ) While you are at it install a thermoswitch on the rubber main engine exhaust hose. The exhaust hose is the first thing to get overheated when you loose seawater flow. The main engine block has so much thermal inertia that it takes a while for it to overheat so the hose may be destroyed (the inner liner cooks and comes loose) before you are aware of a problem. (Don't ask me how I know...) It is a normally open switch, closing at 120 deg F, obtainable at a HVAC supply. This switch is about a inch in diameter with two tabs to attach to a duct and two 1/4" quick connect terminals. I hold it on the hose with a spring around the hose hooked to the holes in the two tabs. Do you have alarms on your engine? I recommend Murphy Gauges; these are gauges with an adjustable contact to feed an alarm (or shutdown on a genset) circuit. I have one for oil pressure and one for coolant temp. Norm S/V Bandersnatch Lying Julington Creek FL ----- Original Message ----- From: JohnChristensen To: [email protected] Sent: 1/27/2010 10:32:54 AM Subject: [Liveaboard] Transmission cooling mind bender Hi everybody I just put in a a new transmission. My engine is a Volvoi MD17C raw water cooled the transmission is a MSB . I have however come up with a mindbending issue and I would appreciate your input. When I cleaned out the other transmission I found a old piece of impeller, almost half a wing stuck in one of the elbows. This surprised me as the transmission water to cool it is before the pump and the engine. I suspect that the transmission cooling has been set up differently when the previous owner had the boat This brings up the point of what is the right order. As it is I have it set up like this Seacock Strainer- Water pump engine- riser-exhaust I had a lot of scale in the old transmission and considering a piece of impeller as well it is a wonder how water came through it. I am considering a different order, actually 2 different ways. 1.Seacock- Strainer- Water pump Transmission Engine- Riser- Exhaust Either that or 2 . Seacock- Strainer Water pump T - (one end of the T to the engine the other to the Transmission) Riser and T to transmission for the exhaust This would eliminate scale build up in the transmission restricting cooling of the engine. In the manual the water is routed from the seacock to the transmission then the pump, but that seems wrong, what do you think Regards John
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