In Hot Water because my wife does not have any!

[Babette04]

I get hot water from my heater when plugged into shore power.
I do not get hot water under way, and the water from the exhaust does not get warm either after running, not under load, for an extensive period of time.
I hear that the heat exchanger can get fouled and my Yanmar had a aftermarket piece from an AC Charging system designed to blow air through the heat exchanger and the coolant out of the system. The piece was aluminum and did not hold-up.
Suggestions? Thanks to everyone who commented on my last post.

 

[CaptainSV-SecondStar]

This article may help:

http://stevedmarineconsulting.com/water-heater-primer/

I have the same/similar issue and own a water heater with a TCV that has apparently failed - the coolant lines from the Yanmar to the TCV are warm, the line running away from the TCV is warm but the warm water is not going through the Hot water tank and the "hot" water line coming from the tank is cool. As this (and other articles) show, you can remove the TCV and plumb the coolant lines directly into the hot water heater (check your manufacturers owners manual; most available online) and then install an aftermarket mixing/tempering valve in the hot water line exiting the hot water heater. I'll probably not do this myself until coolant change next year (just did the coolant change and discovered the issue not noted on survey).

 

[Sailm8]

After installing solar panels we no longer use the motor to charge/make hot water. Bought a solar shower (black bag with about 2.5 gallons of water) Works great if you put it out the day before you need it. I added 10ft of tubing to extend its reach. Good for about 3 days worth of conservative showers.

 

[Bill Roosa]

Check the easy things first. Does the engine have a full charge of anti? Typically the hosing from the engine will go up before it goes down to the HWH. If the coolant is low it will not pump into the HWH. next check the engine operating temp. is the thermostat sticks open the engine will run mostly fine but you will get tepid water from the HWH. Next check the temp of the engine coolant entering and leaving the HWH. Could be a flow restriction (read cut off valve that is closed or partially closed) keeping the flow rate down.

 

[CaptainSV-SecondStar]

Babette - re-reading your post, if your engine heat exchanger was fouled your trouble would be overheating of the engine not a lack of heat use in the hot water heat exchanger, so I would not think that the engine heat exchanger is the source of the issue here. If your coolant is not getting hot enough to open the thermostat on the engine (which is what your description so far sounds like) then you won't be sending any hot coolant to the engine heat exchanger OR the hot water heater. When was the last time you changed your coolant? Did the problem start soon after that? Since you say that you are running cool this might not be an issue but have you checked/replaced your thermostat?

 

[CloudDiver]

In the Military we were often without hot water during field training or ops in OIF/OEF... Baby wipes were a popular solution; one for the junk, one for the pits, and one to hit ya where God split ya. In Grunt Speak it was called a 'Whore Bath'.
I'm not suggesting anyone use that terminology with your spouse... unless you WANT a divorce.