Reality check on non-pressurized cooling system

[gawinger]

In charge of maintaining an 1947 Owens 42', up?graded to twin OMC 165's. Each with a home-built ABS-plastic, vented coolant 'reservoir'. Is this par for a keel-cooler type system? Is a pressurized system proper? There are also no strainers for the raw water system. Doesn't seem right to me. I'm switching from cars to boats and don't know what kind of marine parts/systems are typically found or available to me.<br />Thanks for your help.

 

[coupedeville]

Re: Reality check on non-pressurized cooling system

Post a picture of that boat! Sounds great.<br />Cooling wise, you don't need to pressurize a system for it to work. It really just raises the boiling point, but most boats don't run hot. If it's been working okay for the last 55[!] years, it should work okay now. If you like, make up a strainer, so you don't suck in any unwary seagull's or salmon'. <br /><br />Closed or open cooling system?

 

[gawinger]

Re: Reality check on non-pressurized cooling system

Thanks for the input, coupe. It is a beautiful boat, and I will try to get ahold of a good photo to share with everyone.

 

[DJ]

Re: Reality check on non-pressurized cooling system

merlion,<br /><br />Sounds neat.<br /><br />The closed (pressurized) system will do just what has been mentioned-raise the boiling point. The greater the temp. (up to about 220 F) the greater the efficiency.<br /><br />The PVC SHOULD be able to handle 12 psi. or so.<br /><br />Is this system a complete closed, manifolds and all?

 

[Capt Ken]

Re: Reality check on non-pressurized cooling system

Most of your keel cooled systems are not pressurized. They just have their day tanks located high above the engine so the system stays full and air doesn't get into the lines. Keel cooling is a very easy way to fresh water cool an engine if you never get into shallow water. You still have to have a raw water pump to cool the exhaust, but it can be a very small pump in relation to a pump used for completely cooling an engine. They should be using copper or brass for the under water section of the cooling system because of the heat transfer. I don't think plastic would transfer heat very well. Bad part of keel cooling is if you run aground or hit something floating, you can damage the system and get a leak.

 

[gawinger]

Re: Reality check on non-pressurized cooling system

Thanks all for your input. Conceptually I am with it, I'm just not sure what the heck is going on with the mix of parts on the boat to be more specific.<br />Keel coolers- origional?, <br />Engines- replaced in ~1995, <br />Thermostat housings- appear to be from an all raw-water-cooled system and have lots of blocked-off ports.<br />Resevoirs- homebuilt, atmospheric vented, 4" plastic tanks that steam/stink up the cabin when the stbd engine overheats under medium power. Just air in the system?<br />Raw-water pumps- no raw-water strainers. OK or not? <br /><br />Whats legitimate?<br />Whats reliable?<br />Is it a lost cause, or a case of <br />'whatever works, works'?<br /><br />Thanks again,<br />Merlion

 

[DJ]

Re: Reality check on non-pressurized cooling system

merlion,<br /><br />Capt Ken, is right about the mix of "material" used in the system. PVC does not transfer heat effectively, if at all.<br /><br />Strainers (raw water) are a must.

 

[coupedeville]

Re: Reality check on non-pressurized cooling system

Using plastic for the overflow tanks isn't a problem - just look under the hood of your car.<br />If the whole cooling system's made out of it, well, that's a different story. Finding out what's authentic is going to be a challenge, if you really want to worry about it, that is. I'd worry more about how well it worked, not what it looked like. You need to find someone with experience on an oldie like yours, to help sort out the plumbers nightmare.<br /><br />I'd worry more about your starboard engine overheating under medium power.

 

[geriksen]

Re: Reality check on non-pressurized cooling system

Is it Keel cooled or just Closed cooled?<br />both have an overflow tank...<br />Is there a round heat exchanger on top of the engine?<br />You may just have an impeller out...

 

[gawinger]

Re: Reality check on non-pressurized cooling system

Thanks again everyone for your interest.<br />This is indeed a keel cooled system. <br /><br />On the Stbd engine I have eliminated what appears to be a redundant hose leading from the Thermostat housing back to the freshwater pump inlet (essentially bypassing the coolers by pumping hot water directly back into the block) , as well as a tired thermostat.<br /><br />If the concensus is that an open (non-pressurized)system is acceptable here, my next concern is that the raw-water-style Tstat housing has a passage that is bypassing the thermostat when it is closed, rendering it useless. This passage is designed to move water into the system under pressure from the raw-water impeller-pump, but since it is a fresh cooled system and the raw-water pump is not connected here, there is no pressure acting against the freshwater pump and coolant backflows through this passage, bypasses the thermostat and heads out to the manifolds and on the the coolers. Thus there is no point in having a thermostat.<br /><br />My Questions:<br />Is this worth finding the correct housings to eliminate all the blocked off ports stop this 'leak' and clean things up? <br />Where would I find two crusader freshwater style Tstat housings?<br /><br />Merlion