It takes 1-2 hours to get hot water heated from the engine. Is that normal? Other boaters are telling me that they have hot water within 20 minutes. Hot water heater works fine from shore power. It sounds like some kind of blockage but when flushing the antifreeze I seem to be able to blow through the heater hose without any problem. This has been a characteristic of the boat since I took ownership of her a few years ago. The motor at that time only had 120 hrs on it. The engine is a Yanmar 3YM30 in a 2006 36 ft Hunter. Any ideas would be appreciated.
Hot water issue
- Thread starter nautikaljeeper
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If it's a raw water cooled engine you will never get really hot water. Raw water cooled engines use a lower temperature thermostat in the engine so it never really gets over 140 degrees. Therefore the ability to make hot water by running the engine is pretty dismal.
Heater connections are probably plumbed on the wrong side of the thermostat.. The hot to the tank should come from "under" the thermostat so that block hot water circulated when the thermostat is closed.. I am not familiar with that engine, but I know it is fresh water cooled and should heat the water heater within about 20 minutes. It also may be that the thermostat has failed open.. but that is a low probability. Even so, pull the thermostat and test .. then try to find how the plumbing is messed up.
It took an hour or more to heat our water tank water too. It depends on the capacity of your heater (11 gal requires more heat & time than a 6 gal unit), how hot your engine gets (running at idle doesn't dissipate sufficient heat), how cold it was to begin with, etc..
I'd be amazed if someone really got hot water in 20 minutes
I'd be amazed if someone really got hot water in 20 minutes
I believe it has a 6 gal tank. Engine temp runs at 165-180 depending on rpm range which would be 2500-3000. Water temp would be in the range of 60-70 degrees.
Do you 'burp' you hot water heater regularly/seasonally?
1. If the hot water tank/heater is not burped so that all air is removed it is possible that the coil from the engine will not be totally submerged. With the potable water system pressurized, simply momentarily open the 'pressure relief valve', hold open until all the air escapes, close, do again, to be sure that all air is out of the 'potable water side' of the heater.
2. If the hot water heater is physically HIGHER than the engine ('radiator cap') or if the water heater is 'very high' you will have to 'occasionally burp' the lines that come from the engine or they can become 'air blocked'. The solution for air blocked lines is to apply a tee and a cock-valve at the physically highest portion of the engine hose that runs to (AT) the hot water heater or at where the engine hot water line is at its 'highest'. Open the cock valve to purge any air blockage. Boat Hot water heaters 'should' be installed 'as low as possible' .... so that any air that develops or is trapped in the hosing will naturally flow back to the engine .... and out through the radiator cap and/or reserve coolant tank/'bottle'.
A hot water heater SHOULD have an air bubble at the top of the tank to allow for water expansion. To do this you drain the hot water heater and then close drain and then open a hot water faucet and turn pump on and run until water comes out of hot water side of faucet , this will allow the bubble to be put back in . If you do not do this and there is no air bubble the water will expand and open the pressure relief valve and burp water out. As for the engine heating the water 30 to 60 mon is normal depending on temp of fresh water in tank before starting and also temp of outside water and also thermostat in engine . This is from knowledge I have learned over the last 30 years of dealing with these systems in RV's . Mine takes around 60 min
... and thats why the PRV is located an inch or two below the top of the HW heater - the formation/accumulation of air to a 'measured amount'. Its when the trapped air, in the potable water side, becomes so great that the 'engine coil' is near to totally within the air bubble that the water isn't 'heated' simply because the engine coil isnt fully in contact with the potable water.
Water Heater
There are several ways to plumb the water heater. The most common is the Type 1, similar to your car. Coolant bypasses the thermostat. That is why your car starts giving you heat long before the engine comes up to operating temp. Substitute water heater for car heater core. Types 2 & 3 tap off the cooling circuit going to the heat exchanger. These do not circulate any coolant until the engine gets hot enough to open the thermostat. That could take a while with cold sea water and low rpm. You probably have a Type 2/3 and may even have a bypass valve. Check to see how your boat is plumbed. This link explains it better than I can.
http://sankaty.homestead.com/water_heater_hook_ups.html
There are several ways to plumb the water heater. The most common is the Type 1, similar to your car. Coolant bypasses the thermostat. That is why your car starts giving you heat long before the engine comes up to operating temp. Substitute water heater for car heater core. Types 2 & 3 tap off the cooling circuit going to the heat exchanger. These do not circulate any coolant until the engine gets hot enough to open the thermostat. That could take a while with cold sea water and low rpm. You probably have a Type 2/3 and may even have a bypass valve. Check to see how your boat is plumbed. This link explains it better than I can.
http://sankaty.homestead.com/water_heater_hook_ups.html
RichH and others,
at the risk of subverting this thread I would like to ask a question.
The previous owner of my HC 37 with 3Qm30F yanmar had attained water heating by running a connection from the outlet of the engine block to the water heater and then back from the water heater to the inlet to the thermostat. The problem I had with that is that it replaced about a foot of about 1 inch (or biggger) hose with about 10 feet of 1/2 inch hose. It seemed to work OK and we got plenty hot water, but it was a mess of galvanized pipe fittings and I was concerned that the water eventually reaching the thermostat may be over cooled, resulting in the thermostat opening too late and the engine overheating.
So I restored it to Yanmar factory original - if has anyone confronted this issue and has any comments I would be grateful? The admiral and I would love to get hot water under way.
at the risk of subverting this thread I would like to ask a question.
The previous owner of my HC 37 with 3Qm30F yanmar had attained water heating by running a connection from the outlet of the engine block to the water heater and then back from the water heater to the inlet to the thermostat. The problem I had with that is that it replaced about a foot of about 1 inch (or biggger) hose with about 10 feet of 1/2 inch hose. It seemed to work OK and we got plenty hot water, but it was a mess of galvanized pipe fittings and I was concerned that the water eventually reaching the thermostat may be over cooled, resulting in the thermostat opening too late and the engine overheating.
So I restored it to Yanmar factory original - if has anyone confronted this issue and has any comments I would be grateful? The admiral and I would love to get hot water under way.
Sounds like you need to blead the hot water heater as in you have a air block, most likely at the lowest spot in the hose to the heater or entry port into the heater. Some systems even have a bleader value plumbed in for this. With the conditions you present the water should be hot in 30 min the most after the engine gets to operating temp.
I would check the thermostat on the motor first if your motor doesn't get hot enough your heater never will
All of the responses I've seen make sense, but none of them quantify the situation very well. I have an inexpensive infrared thermometer, and have used it to benchmark my main engine cooling system. I have a Catalina 28 with a Universal M25XPB engine. The normal engine temperature is 162F. I know that the input to the heat exchanger is about 170F, and there is a 30 degree drop across the heat exchanger when the lake water is about 65F.
A similar process could be used to troubleshoot the heater problem. When the engine has come up to temperture, you could use the thermometer to measure the temperature of the hose going to the heater as it exits the engine, the temperature of the antifreeze input to the heater, and the temperature of the antifreeze output of the heater. You could also measure the temperature of the hot water pressure system as it exits the heater over time by running the tap for 5 seconds, measuring the temperature at the exit of the heater, and repeating the measurements every 5 minutes or so.
If the input temperature to the heater is substantially lower than the exit from the engine, you probably have low water flow in the antifreeze, and the engine heat isn't getting to the heater.
There should be a significant difference between the antifreeze input and output when the hot water tank is cold (heat should be transferring to the tank). If there is little difference, either the antifreeze isn't flowing (see above), or something is preventing heat transfer in the tank (low tank level, plugged tubes, or if you have a winter bypass switch it may not be working right).
Good luck.
A similar process could be used to troubleshoot the heater problem. When the engine has come up to temperture, you could use the thermometer to measure the temperature of the hose going to the heater as it exits the engine, the temperature of the antifreeze input to the heater, and the temperature of the antifreeze output of the heater. You could also measure the temperature of the hot water pressure system as it exits the heater over time by running the tap for 5 seconds, measuring the temperature at the exit of the heater, and repeating the measurements every 5 minutes or so.
If the input temperature to the heater is substantially lower than the exit from the engine, you probably have low water flow in the antifreeze, and the engine heat isn't getting to the heater.
There should be a significant difference between the antifreeze input and output when the hot water tank is cold (heat should be transferring to the tank). If there is little difference, either the antifreeze isn't flowing (see above), or something is preventing heat transfer in the tank (low tank level, plugged tubes, or if you have a winter bypass switch it may not be working right).
Good luck.
There will probably be no functional difference as to thermal control of the engine during 'normal' operation, the thermostat will simply 'correct' the thermal regulation of the engine block; however, -
1. once the entire system becomes 'heat soaked' during 'steady state' operation the T'stat will tend operate normally.
2. The engine was designed around 3/4" in this FW cooling loop, the 1/2" diameter hosing will affect the mass transfer of cooling water (high resistance) and eventually I would assume that you wont be able to run the engine at or close to 'wide open throttle' for very long before the engine overheats because of the reduction of water flow due to the 'capacity' of water flow has been reduced when at high rpm. Reduced flow of FW in the Heat Exchanger is going to be the 'culprit' when at higher engine rpm ... youve probably limited your Hx's 'reserve capacity' with the 1/2" FW lines.
Donnybrook has the right idea. This is something I researched recently. As he said, you don't want to be hooked into the heat exchanger loop. In some cases, under load that can lead to overheating of the engine because of the extra resistance with all that hose. Most engines ( e.g., Westerberke/Universal ) have a short hose connected between the top of the engine's water pump and the head. This is the thermostat bypass that keeps the water circulating in the block until the thermostat opens. Remove this short hose and hook up the water heater hoses here.
Our 2004 44DS had the same issue, where it took seemingly forever to heat off the engine. We checked for air bubbles in the line that ran from the engine to water heater, we removed the hot-water shutoff (this came with the Force-10 water heater) on the engine loop to the water heater, nothing seemed to fix the problem. Eventually I made enough noise that the dealer replaced the hot water heater under warranty, which fixed the issue (it had always worked off shore power).
After they replaced the water heater, I looked at the temperature control device that was taken off the old water heater and noticed a large amount of calcium build-up on the potable water side. What I suspect had really happened was that the calcium build-up on the heat exchanger inside the water heater had essentially formed a layer of insulation between the surface of the exchanger and the water.
After they replaced the water heater, I looked at the temperature control device that was taken off the old water heater and noticed a large amount of calcium build-up on the potable water side. What I suspect had really happened was that the calcium build-up on the heat exchanger inside the water heater had essentially formed a layer of insulation between the surface of the exchanger and the water.
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