The flow diagram you attached is for a TCV equipped tank only and yours has no TCV installed so that diagram is not helpful in your case.
Here is the schematic for water flange group on the M25XP. You are correct about the pin hole. That is why I cannot figure out why the engine will not heat up. I have contemplated temporarily replacing the thermostat with duct tape to stop all flow to see if it will heat up. the low coolant temp has me stumped.If your bypass valve is your engines t-stat, and the engine never gets to 160F in order to actually open it, your only flow is through the pin hole in the t-stat. ? Can you post a photo of where you are physically connected to your engine?
Here is the link to my owners manual http://www.suremarine.com/manuals/assorted-information/kuumawaterheaters.pdfBy vertical layout I mean the height of the water heater relative to the motor coolant reservoir.
Kumma manual mentions this:
"If you are using the heat exchange feature, locate the water heater as close to the
engine as possible. The heat exchanger port (or TCV inlet if equipped) must be
lower that the coolant output port of the engine.
Since your water heater is apparently above the motor coolant reservoir, why not call Kuuma and ask them why they require that the water heater vertical position must be below the reservoir.
(from following post) The flow diagram you attached is for a TCV equipped tank only and yours has no TCV installed so that diagram is not helpful in your case.
Charles
I have been trying for years to heat the water with the engine but on my boat it just doesn't work. I have an older tread trying to solve that problem. http://forums.catalina.sailboatowners.com/showthread.php?p=1133153&highlight=hayden
in a test last year I got a 3º rise in outlet temperature after an hour of running at cruise speed. The coolant loop from the engine drops from 140º to 134º across the exchanger in the water heater. I have a RedDot heater down stream in this loop and the coolant temp drops from 134º to 97º across it even though the fan is not running.
It is a force 10/Kuuma 6 gallon heater. I have checked for flow in the loop and it is unobstructed. There are no bubbles in the system (purged with continuous flow from an axillary pump.) I used an optical scope to inspect the inside of the tank for buildup on the heat exchanger and it is clean.
Last year I motored for 6 hours and got warm water. The Admiral is not happy.
It is just a loop through the water heater. As long as hot coolant is flowing through the heater I don't think this would make any difference.Hayden,
This may sound simplistic , but you might have the inlet & outlet hoses reversed at the heater. The labeling might have been incorrectly applied at the factory. Doug Ward
Hayden,
This may sound simplistic , but you might have the inlet & outlet hoses reversed at the heater. The labeling might have been incorrectly applied at the factory. Doug Ward
That's right, it does NOT make any difference.It is just a loop through the water heater. As long as hot coolant is flowing through the heater I don't think this would make any difference.
That would be true if the water coming out of the engine kept getting cooler but according to Hayden there is a steady inflow of water at 140 degrees so that would mean that the temperature inside the coil stays at a temperature between 140 and 134 degrees Fahrenheit which the manufacturer states should be adequate to heat water inside an hour. When I was a teenager I removed the thermostat from a car engine and as a result the car started overheating. A old mechanic told me that the water was flowing too fast through the radiator and not cooling enough so temperature built up. The radiator was working at capacity but was overwhelmed by the added volume of hot water. In this case the heat exchanger is not being overwhelmed it is working at minimum efficiency.I didn't go back and read all replies, but could it be the water is moving too quickly through the water heater, and not allowing heat ransfer? I don't ecall anyone mentioning fins on the heat transfer tube, so guess it's just smooth-walled?
The coil temp can stay between 140 and 134 degrees without the water in the heater getting up to temp in a reasonable period of time, it all depends on how much heat conductance the exchanger provides. If it's a good insulator, very little heat will be transferred regardless of how hot the water is on either side of the exchanger.That would be true if the water coming out of the engine kept getting cooler but according to Hayden there is a steady inflow of water at 140 degrees so that would mean that the temperature inside the coil stays at a temperature between 140 and 134 degrees Fahrenheit which the manufacturer states should be adequate to heat water inside an hour. When I was a teenager I removed the thermostat from a car engine and as a result the car started overheating. A old mechanic told me that the water was flowing too fast through the radiator and not cooling enough so temperature built up. The radiator was working at capacity but was overwhelmed by the added volume of hot water. In this case the heat exchanger is not being overwhelmed it is working at minimum efficiency.
That is what I said the manufacturer's representative had indicated that 140F was adequate temperature to heat water within an hour. I agree that efficiency of the exchanger is a primary concern. Regarding the thermostat story it was true that the overheating took place when the engine was ran over a certain RPM. Until then the radiator was able to cope with the increased flow of heat arising from the increased volume of passing coolant. Above that RPM range the radiator was working at its maximum capacity and was overwhelmed and the circulating coolant was increasingly gaining in temperature in subsequent passes as the coolant entered and exited the engine. The net effect was as if we had installed a smaller radiator inadequate for the task at hand. I just wanted to illustrate the point that speed of the flow may affect the temperature of the coolant in the loop but if the inlet temperature to the exchanger remains constant then it is up to the efficiency of the exchanger to do the work. The radiator indeed was designed to work with a thermostat to cool the engine. By removing the thermostat I fouled up the design criteria. If we slow up the flow in Hyden's heater we could probably get an exit temperature of 120 but no more heat would be transferred into the tank as then the average temperature in the coil would be the around 130F instead of the current 137 F. You and I are basically saying the same thing but from opposite perspectives.The coil temp can stay between 140 and 134 degrees without the water in the heater getting up to temp in a reasonable period of time, it all depends on how much heat conductance the exchanger provides. If it's a good insulator, very little heat will be transferred regardless of how hot the water is on either side of the exchanger.
Regarding the thermostat story, I think you've broken at least one law of thermodynamics. The radiator may transfer less heat per pass if the fluid is moving faster but by the same token, the engine will transfer less heat to faster fluid too. By design, the radiator can dump more heat than the engine can produce. If that weren't the case, the engine would overheat at a given throttle setting and above. My guess is that when you pulled the tstat, you introduced air into the system and prevented coolant flow through the radiator, causing the engine to overheat.