Water Heater Coolant expansion tank

[SV Alfresco]

The water heater I'm installing is higher than the engine, a Yanmar 3jh5e, and I need to replace the coolant expansion tank that goes above the water heater. The one I pulled out is made from a fiberglass type material, and looks much older than the engine. It's been sitting loose on top of the old water heater since I got the boat. I want to replace it with metal if possible since it's pressurized.
Does anyone know where I can purchase an expansion tank that is right for this? I have spent hours searching the web but have not come up with much. From what I can surmise, the tank should be higher than the heater and have a pressure cap with a lower rating than the one on the engine. What those pressure ratings are, I'm not sure. I've read 14 and 7, and 14 and 13.

Thanks,
Mike

[PeteW]

Have you looked at blow molded automotive tanks. I'm using a VW expansion tank on my Westerbeke. I mounted it so I can get to the cap when I open the lid under the companionway. I also went to the extra trouble of connecting the vent hose to the thermostat housing. Helps to burp the motor when I flush the coolant.

Pete

[PeteW]

Turns out I'm using a Volvo 760 tank and cap. Not VW as originally stated.

http://www.boatpartsandspares.co.uk/volvo-penta-cooling-system-expansion-tank-1761-p.asp

You'll be happy to know that it's also the same tank used by Volvo Penta on the 2002 marine diesel engine. But if you can get one from a junk yard the mounting bracket for the tank is worth snagging. It comes off with a 10mm wrench.

Pete

[SV Alfresco]

I found a tank. It's called a surge tank, as opposed to a coolant recovery tank which usually is made of plastic. The manufacturer is Sen-dure. It's made of heavy metal and comes with a 7 psi cap. The one I got is 3 or 4 quarts, not sure of the exact capacity. Picked it up at a marine service company in Newport,RI that does a lot of re-powering jobs. Now the trick is how to mount it and everything else. All this is going to require some planning and construction. Think I will loop the engine coolant hose back to the engine for now so I can use it and get some sailing in. Some other things to do is to add a thermostatic controlled mixing valve and some sort of manifold system to organize the water lines going to the shower and faucets. This is bigger than a weekend project.

Thanks for all the replies,

Mike