Not all water heaters work like that. What came with our boat had the entire supply of engine cooling water going through the water heater and then back to the engine. There was no separate loop for it. In our case small hose would have been bad. The hose ran from the exhaust manifold to the water heater and then from the water heater to the exhaust pipe injection point. Yes...they ran salt water through the heater. Amazingly enough that didn't kill it, it rusted from the outside instead.
Joe Della Barba Coquina -----Original Message----- From: CnC-List [mailto:[email protected]] On Behalf Of Wally Bryant Sent: Wednesday, February 26, 2014 5:17 PM To: [email protected] Subject: Re: Stus-List Isotemp hot water heater (35-1 install) FWIW I learned a couple of things when installing my new hot water heater. The most important was the hose size. I originally thought that I should use a nice big hose to avoid creating a pressure problem. I was thinking that a big hose would have less resistance and would allow maximum coolant flow. So I ran 3/4" hose. I thought I was being smart, because after moving the water heater amidships it was a long hose run that went under the cabin sole. Well, the engine overheated every time I tested it. So I talked with a trusted mechanic who said "Didn't I tell you to use 3/8" hose when we talked about this last year? I even told you where to get it locally! The water (coolant) pump doesn't generate a lot of pressure." Apparently the way my engine is designed, the water heater ports are set up so that coolant can flow through the engine first, and if there's any extra pressure it'll work its way to the water heater and back. Looking at the service manual and exploded parts diagrams, it's true. I'd actually looked really good at it before hooking things up, and it didn't make a lot of sense to me at the time because it was clear that there was a straight path through the engine and I couldn't see how coolant would also get to the water heater if there was an easier path back to the engine block. Anyway, I ran 3/8" hose to the water heater. The cool thing is that my dumb mistake worked out to the boat's benefit, because the OD of the 3/8" hose was less than 3/4" and I was able to work the smaller hose inside the bigger hose, using the existing hose run that I'd already drilled holes for and pulled. The big hose was wire reinforced Trident exhaust hose, and I probably have the ultimate chafe protection on the coolant hose to the water heater. That's fine, since it runs under the cabin sole and through a few fiberglass elements. Bottom line is that the mechanic was right. The top priority is to keep the engine cool (duh) and enough coolant works through the little hose to the water heater. For me it takes less than 1/2 hour to get it to engine temps. Regarding air locks, I have pushed the edge on that. I bought an 'auxiliary coolant tank', that can be mounted high, when doing this project, just in case I needed it, but I didn't because through a divine miracle the water tank ended up being about two inches below the top of the coolant cap on the engine. (Of course that depends upon who's sitting where, and if all the crud on the boat is managed to keep the boat on her lines.) Nonetheless, I've had a few air locks, too, and they will cause overheating. When installing the water tank, I made a ball valve assembly near the engine that lets me turn off coolant to the water heater and send it right back to the engine. I think I built that when I was trying to figure out why the 3/4" hose wasn't working, but really don't remember. Early Alzheimers. I have used the valve assembly to troubleshoot overheating questions since then. It's nice to be able to take the water heater out of the problem. To date, overheating has been 1) broken belt (That's what I get for replacing a perfectly fine belt) 2) fish sucked up into the water intake hose 3) stupid mistake 4) stupid mistake 5) I don't remember, but it was probably a stupid mistake. Wal dwight wrote: > I had difficulty getting the coolant to flow uphill from the engine when my" > tank was mounted high just suspended from the bottom of the shelf in > the cockpit locker (port side on the MKII) I think because of airlocks. _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected] _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected]
