I have a 1982 Hunter 33 that is raw water cooled and doesn't have a heat exchanger. can one be added to give me hot water on the hook?
Hot water away from dock
- Thread starter mitchf
- Start date
- Status
My buddy's '78 33 is raw water cooled as yours is and he has a hot water system. It doesn't get as hot as fast as one with an exchanger, but works pretty well.. I may be around his boat tomorrow so I will take a couple of shots to show the hook-up. Looks like two pipe plugs were pulled and hose barbs attached .. hoses hooked to the tank and there it is.. The other question .. yes you can install a fresh water cooling system for the engine but it will be pretty expensive .. there are kits available with most of the parts in a bundle .. Someone on this site may have a link..
Yes, you can add a heat exchanger depending upon the size of you bank account. 
My original 2QM20 had been converted, I think at the factory. Besides the heat exchanger you will need the pump, a way to mount it, and the longer belt.
Mine just had a piece of one-inch angle iron bolted to the block and then the pump bolted to that. You can find the heat exchanger online. Pump too.
In the pictures you can see the heat exchanger with water fill on top left. I had started to remove the pump in the second picture thus the piece of angle just hanging there.
My original 2QM20 had been converted, I think at the factory. Besides the heat exchanger you will need the pump, a way to mount it, and the longer belt.
Mine just had a piece of one-inch angle iron bolted to the block and then the pump bolted to that. You can find the heat exchanger online. Pump too.
In the pictures you can see the heat exchanger with water fill on top left. I had started to remove the pump in the second picture thus the piece of angle just hanging there.
Attachments
Ahh Haa.. Thanks for the post, Ed !! On my buddy's boat, the hot water tank is in place of the little jumper hose just in front of the closest yellow oil cap in Ed's picture .. The hose comes from that right side hose fitting, goes through the hot water heat exchanger, then back to the front of the exhaust manifold hose fitting where the little jumper terminates.. If ya want to do the hot water without the engine heat exchanger, that is how you'd hook it up..
Last edited:
Thanks. But what kind of hot water system does he have? A tank with an exchanger? Thanks
I think Claude's friend simply plumbed his raw water-cooled engine through a hot water tank. It is easy to do as Claude explained. But maybe there is a change in thermostats involved. Because most who have tried it find that it takes way too long to just get luke warm water.
The heater is something like this one.. http://www.defender.com/product.jsp?path=-1|51|10172|319680&id=1110826
The engine hot water is plumbed through the tank exchanger which heats the shower and sink water. There are quite a few manufacturers of tanks and many different configurations, so you have to carefully pick what is correct for you and your boat.. Ed, this one has the normal (140F, I think) raw water thermostat and because of the 2QM design of passing all the engine hot water through the heater, it works pretty well.. but you are correct in that the engine has to be run a while (half hour or so) to get the tank hot..
The engine hot water is plumbed through the tank exchanger which heats the shower and sink water. There are quite a few manufacturers of tanks and many different configurations, so you have to carefully pick what is correct for you and your boat.. Ed, this one has the normal (140F, I think) raw water thermostat and because of the 2QM design of passing all the engine hot water through the heater, it works pretty well.. but you are correct in that the engine has to be run a while (half hour or so) to get the tank hot..
If you get raw salt water hot enough to provide decent domestic hot water heat, you will have trouble with deposits in your engine cooling passages. For this reason, a higher temperature thermostat isn't available for my RW cooled Yanmar. You need a FW cooled engine for engine heated water to be practical.
I notice you found the on demand propane thread from last year. I recommend you read through the entire thing. It has opinions from every which way AND loose, but I think you get a good overall idea of the issues. I think the "approved" list is a decent guide, but there is probably no one here who has only approved items on their boat. The key, in my opinion, is to do it smart with plenty of backups. If the Excel on demand is installed correctly with propane and CO detectors, AND used smartly it should be fine.
Meanwhile, like Roger said, good luck getting enough heat off an exchanger with that motor unless you have FW. It runs too cool (a good thing!) to heat water for use.
We don't know the engine model of the original poster. But if its the QM series, I've discovered that its not possible to change thermostats from the 140F raw water cooled version to a ~170F type. This is because Yanmar's 140F thermostat model is a different size/shape than the higher temp version. For the original raw water designed engines, the thermostat housing molded into the exhaust manifold will only accept the 140F size. This makes a lot of sense to prevent people from unwittingly upping to 170F with salt water coursing through the engine. As Roger Long commented, the internal cooling passages will plug up with deposited salts and minerals. I've read that its almost impossible to later clear these out.
Since I had the heat exchanger/anti freeze conversion, and deposits aren't an issue, I've asked several Yanmar repair and dealer types if there is a work-around to increase to 170F operating temp. I was told no. Even if someone cobbled together (say) an external thermostat 170F housing, I've observed that the pressure release cap on the converted engines is a low 5-7 lbs. This would have to be changed, and an overflow tank added. And don't forget to change out the 140F temp alarm switch!
I've recommended to the QM owner who is going to buy my hot water tank that he simply reroute the RW flow directly to the elbow an cap the head exchanger connections. A pinhole or crack developing in the heat exchanger when the engine was off could let the FW pressure fill up the muffler and then back up into the engine waterlocking it. The next start attempt would them be exciting and perhaps damaging.
Is there a concern that the salty raw water would cause corrosion in the water heater and ruin it after a few seasons? Ed H
- Status