Diesel exhaust- water? - Page 3 - SailNet Community
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post #21 of 27 Old 06-14-2006
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Sorry to sound contrary Sailingdog but any closed cooling system needs to shed heat and this can only be done through some form of heat exchanger. In an automobile, the heat exchanger is in the form of an air cooled radiator. In a boat it is done through a heat exchanger that has coolant on one side and raw water on the other. I have never seen any other form of cooling system and I've surely not seen any boat with an aircooled system.
If it needs raw water, it will splash out of the exhaust (unless the exhaust is underwater - rare).
I agree with previous thread that a closed system will allow quite extended running before causing damage (maybe not 20 minutes!) but this will definitely show on the temp guage (unless of course that's faulty as well). Another contributor to running longer will be if the hot water cylinder is also in the form of a heat exchanger, this will absorb quite a lot of heat energy depending on it's size as will a refrigerant heat exchanger. Lots of variables.
This is surely a strange one. If the fairer is going to be keel hauled, hold him down there long enough to put another strainer on.
I never allow my engine to run more than a minute without seeing water puffing out.

Last edited by Omatako; 06-14-2006 at 04:15 AM.
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post #22 of 27 Old 06-14-2006 Thread Starter
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For those concerned on how the engine could run 15-20 minutes and not overheat, I have a theory
The engine has a closed, fresh water-antifreeze cooled system. This is designed to transfer heat to the raw water and discharge the raw water through the exhaust. Closed system was full of coolant so probably temp gauge was accurate
But boat also has an engine heated hot water tank. I think that the drinking water in the hot water tank had sufficient capacity to aborb engine heat for 15 minutes and prevent overheating. Cooling system opened the thermostat at 175 and then held there as heat was transferred into the tank. Water in tank got warm, but not hot. If we had continued, I am sure all the problems suggested might have occured
Will know more this weekend
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post #23 of 27 Old 06-14-2006
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MBesant, you probably have that right and were very fortunate not to have run any longer, I suspect that 15 - 20 minutes would be the limit unless you had a very large hotwater tank that was quite cold to start with.
Our last boat allowed us to isolate the water tank from the cooling cct, and I remember watching the temperature of a warm engine plummet when we put the water tank back in the circuit - which prompted us not to do that again, the thermal shock can't be good for anything.
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post #24 of 27 Old 07-17-2007
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Quote:
Originally Posted by camaraderie
There's no need to replace an impeller that often...especially if you buy the good ones (Globe - as I recall.) We consistently get hundreds of hours from our impellers. The real enemy of impellers is winter layups and lack of use (and of course...closed thru hulls!). Once a year is plenty of changing for most uses.
Cam,

Be very, very careful with the so called "better" Globe impellers. I have tried three, in two differnt boats and all three of them spun off the PLASTIC center hub. Yes the rubber never did fail but that's because it could not spin! IMHO Globe impellers are a problem waiting to happen! Use the stock impeller and make sure you're getting water flow and you'll be fine. I change mine each spring!

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post #25 of 27 Old 07-17-2007
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Quote:
Originally Posted by swanfrogg
Anyone knows how to test if a temperature sensor and the temperature switches in the thermostat housing are functioning correctly?
Thank you
Yes it's caled an infrared thermometer. Simply aim it at the thermostat housing, read it, and compare it to the temp gauge.

Below is a link to the one I own & use for lots more than just engine stuff. You can even shoot it overboard to know the water temp... I bought it a Napa Auto for $59.00!

Raytek MiniTemp MT-4 InfraRed Noncontact Thermometers - Test Equipment Depot

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post #26 of 27 Old 07-17-2007
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Halekai...we've been using globe with excellent results for some years now in two different boats/engines and none of the problems you report. It seems that some swear by them and have no problems and others hate them and have had problems. Maybe it is the individual models and applications rather than a "global" (g) problem.
I guess since they are all cheap...it might be best to carry one standard and one globe spare.... Getting the performance of the globe if possible but being ready with an alternative if not.
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post #27 of 27 Old 07-18-2007
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Quote:
Originally Posted by halekai36
Yes it's caled an infrared thermometer. Simply aim it at the thermostat housing, read it, and compare it to the temp gauge.

Below is a link to the one I own & use for lots more than just engine stuff. You can even shoot it overboard to know the water temp... I bought it a Napa Auto for $59.00!

Raytek MiniTemp MT-4 InfraRed Noncontact Thermometers - Test Equipment Depot
Here's an even easier way: remove them from the donkey and plonk them into a pan of boiling water. If the thermometer doesn't read 100 degrees Centigrade, it's duff.

Next, let the water cool: As you do so, monitor when the thermostat that you've also removed from the donk closes. Compare this temperature (read off the 2-buck Mercury thermometer you've bought earlier) that's quoted in the workshop manual for your weather conditions / ambient temperature range. If they're different, replace the thermostat!

BE
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