Hose run for Engine to hot water heater 34' pilot

[BB-marine]

I have a 34' 2002 pilot. The hot water heater is located under the forward Dinette seat. Mainship did not utilize the tank het exchanger. The only resource for hot water is 120V power. We like to anchor more than stay at marinas. I'm not a fan of cold showers. We did the Loop last year with this configuration. I do have solar (600W) and I do have a 3000W inverter. Twin engines that can help with battery charging while under way. Our resource last year for hot water was while running with engines and solar with good output. Turn the water heater on. This uses about 70amps. A lot of 12V dc power. Between the 50 amp alternator that puts out about 35amps and the solar controller which averages 35 amps when in bulk charge we could maintain battery Voltage but barely. We have a refrigerator \, freezer, electronics ...... all using amps too. This method worked but it is not efficient. We do not have a generator installed. We do carry a 2200 watt Honda that will power the hot water heater but I'm not a fan of using it when we are underway or if the anchorage has a number of boats anchored. I'm do not like running it because of noise. The efficient way to have hot water is to use the engine closed cooling and the the hot water tank heat exchanger. The issue I am having is finding a path to run the hoses. Mainship build has solid bulkheads glassed to the hull so passage forward is limited and the areas of access seemed to be used. This is a twin engine model so the 250 gallon fuel tank spans the full beam of the boat forward of the engines. If you have this model twin engine and have closed cool water hoses going to the water heater can you advise me as to where the hose runs are? Thank you.

 

[JohnP]

Don't know anything about Mainships, but if you could move the water heater to the engine space it would be easier to plumb the engine coolant loop.

 

[DavidM]

Don't know anything about Mainships, but if you could move the water heater to the engine space it would be easier to plumb the engine coolant loop.

But then, you would have the same problem with running the cold input and hot output lines. Plus with twins I am sure that there is no room for a water heater in the engine room.

I had a Pilot 34 single but for a twin I can’t help with hose routing.

David

 

[BB-marine]

Yes the option to move the water heater into engine compartment will work. There is plenty of room for it . The fuel tank is forward so there is 30" between the engine and the hull both sides. Working on the engines in this boat is a breeze. I installed a 20 gallon water tank on the outboard side of port engine. This tank is used for the head flush water. I left the raw water flush head in the boat but plumbed it to a fresh water tank. I have plenty of room on the outboard side of Starboard engine. My goal was to try to leave the tank in original location for weight and plumbing. The water filter and pump are located in the same compartment as the water heater. I am hoping that a 34 pilot owner found the path. I have looked with a bore scope to find a path. The only path I found was through the head under the galley. This is the route that all plumbing lines use. It is tight to pull two heater hoses through.

 

[JohnP]

Are boats are different but I do have twin engines and a 12 gallon Raritan water heater fits well. If you have hot and cold lines leading to a cockpit shower could you not use those lines to feed the hot water system without adding more water lines?

 

[BB-marine]

No hot water lines past the head. There is a cold water line for wash down in the cockpit. I have the plan that you suggested as plan B. My hope was to find a Pilot owner that has the exchanger in use at the original hot water tank location. There is a Mainship pilot owner that claims he did this hose install on FB. When I reach out and ask where and how. He is not able to answer??? I have spent hours trying to find a path forward without going to plan B. Thanks for your suggestion.

 

[DennisB1]

Look at Sure marine (Seattle) on their hydronic heating systems. Set up a circulating pump a heat exchange for both engines a small expansion tank as show in the hydronic heating systems. The hot water tank will need a mixing valve to cool the hot water to 120f. Maybe add a cabin heater also.
This this approach could heat your hot water tank to the 170f range in several hours of engine run time. The high temperature is the reason for the mixing valve. It is a mini heating system minus the furnace. The existing hot water tank could to remain in its current position.

 

[Duetto]

we've had engine heated hot water for 18 seasons. you'll get 180 degree hot water very quickly if your engine temps get near 180.

 

[BB-marine]

Where is the water heater and where are the hoses run to get to the heater?

 

[Comodave]

Why not just drill some holes in the bulkheads to get to where you need to?

 

[Irish Rambler]

When we bought our current boat the hot water tank was T'eed off the engine. The problems were that it would burn you when the engine was running but would not keep the heat overnight.
You will find there will be enough room betweeen the side of the engine and the hull to fit an insulated hot water tank. Connect this to your heat exchanger. Make sure the new hot water tank has a mixing valve on the outlet so you can regulate the output temperature which also conserves the heated water. A very important point is to keep the top of the hot water tank level with the top of the engine otherwise you will get thermal convection and although your engine will be lovely and warm your shaving & shower water won't.
With this setup your water will stay warm overnight and suitable for a hot shave and shower the next morning.
A 20 minute run under load on the engine connected to your hot water tank in the morning will bring it up to temp, reheat your water and recharge your batteries.
I have no knowledge of your chandlers in the states but if you look up www.asapsupplies.co.uk and check out their 'Hotpot' calorifiers you will see what I'm referring to, they may even have an agent in the US.

 

[BB-marine]

Why not just drill some holes in the bulkheads to get to where you need to?

That would be an easy task if I did not have a 250 gallon fuel tank in front of the bulkhead. The fuel tank spans beam to beam. There is a cable run on the starboard side top of the tank. A hose run port side top of the tank. Theses runs are full and there is limited space for two 3/4" heater hose. My question was to someone that owns this model 34' Pilot and has the heater plumbed to the engine. Where is the run for the hoses that they used or the factory. I am completely aware of the use of the tank when it is plumbed to the engine cooling system. I have had several boats in the past with this function. Thank you.

 

[Shrew]

We have used a Honda 2K for many, many years. Get in your dinghy and drive a little ways away, then shut off the dinghy motor. You can BARELY hear them from 100 feet away. Hundreds of times we've been anchored in crowded anchorages with other people running and have never found them to be an issue.

I would find a way to hook-up the heat exchanger to the water heater. Follow the water lines. My antifreeze lines run right beside my cold water feed to the water heater.

 

[Tonic1]

I have an 07 P34 with twins and the same water heater location. I have thought about this project, but never followed through on it. My cabin AC is under the rear dinette seat and the raw water line travels under the fuel tank and into that compartment. You might be able to feed from there through the center dinette seat compartment and into the area of the WH.

Alternatively, the water line to the wash down goes into the head area, and the supply for it and the head has to come from the pump which is located with the WH. I'm thinking there is passage through the central bilge where the water tank is. Maybe you could run a snake through that area and pull your hoses thru there.

If you figure it out, I'd like to know what you end I p doing.

 

[BB-marine]

I have an 07 P34 with twins and the same water heater location. I have thought about this project, but never followed through on it. My cabin AC is under the rear dinette seat and the raw water line travels under the fuel tank and into that compartment. You might be able to feed from there through the center dinette seat compartment and into the area of the WH.

Alternatively, the water line to the wash down goes into the head area, and the supply for it and the head has to come from the pump which is located with the WH. I'm thinking there is passage through the central bilge where the water tank is. Maybe you could run a snake through that area and pull your hoses thru there.

If you figure it out, I'd like to know what you end I p doing.

You have the same set up as I do. Solid bulkhead center bilge. There is a dedicated bilge pump for the forward bilge. Mainship kept the engine compartment sealed between the living quarters and engines. That would have been an easy run. I may remove the dinette back cushion starboard side. This is where the air duct runs from marine air to the forward berth area. If I remove the engine throttle/ shift binnacle and fiberglass housing I may have access to run the hoses in that area behind the seat back cushion. I thought for sure a 34 pilot owner would have done this project. I have to wonder why Mainship didn't do it? It is the first boat I have owned that did not utilize engine coolant to heat the water tank.

 

[Bacchus]

There are many builders that don't make the engine to WH connection eventhough they install HWH with heating coils. My guess it is a liability/:warranty avoidance issue.
My MS 34HT WH has coil but not connected to engine cooling.
Our fuel tank is nearly full width but sits above main fore / aft stringers. There are 2 PVC "conduits" through the midship bulkhead for wire & cables running fwd to thrusters, anchor winch, etc. There must be some passage for wires, cables & pex for aft deck washdown / shower... maybe below the fuel tank!

 

[Rearmount]

You have the same set up as I do. Solid bulkhead center bilge. There is a dedicated bilge pump for the forward bilge. Mainship kept the engine compartment sealed between the living quarters and engines. That would have been an easy run. I may remove the dinette back cushion starboard side. This is where the air duct runs from marine air to the forward berth area. If I remove the engine throttle/ shift binnacle and fiberglass housing I may have access to run the hoses in that area behind the seat back cushion. I thought for sure a 34 pilot owner would have done this project. I have to wonder why Mainship didn't do it? It is the first boat I have owned that did not utilize engine coolant to heat the water tank.

There is room doing exactly as you say. I ran new wiring up to vberth and back to fusion stereo for amplifiers and tv connections. I used a piece of pex tubing to start the snake from engine room.

 

[wkearney99]

While it seems like using engine coolant to heat the water seems like a good idea, it's not without risk.

Mainly, if any part of the loop fails you risk serious engine damage from overheating. We had the hose fitting at the engine fail during delivery of our EB47. Puked $400 worth of coolant all over the engine compartment. It was only by luck that it happened while heading into a fuel dock, one that actually had enough of the specific coolant on-hand to refill it. That and threaded plugs that I put in the engine, never to reconnect that loop! It's likely ours failed due to vibration. The hose wasn't as well-supported as I'd have liked, and must've allowed just enough movement over time to cause the fitting to fail. That and how it was routed seemed like it'd have gotten pushed on during other maintenance, likely further risking stress failure.

And most boats don't have thermostatic regulators on the plumbing fixtures. You risk getting a serious scalding burn from water heated by engine temperatures.

Lastly we've had water heaters fail (in past boats) and ended up with coolant lost into the hot water system. Bad for the engine, bad for the water system (potentially poisoning from engine antifreeze) and ended up being more work/money out of my pocket.

Hard pass on ever having that setup again.

 

[BB-marine]

There are many builders that don't make the engine to WH connection eventhough they install HWH with heating coils. There must be some passage for wires, cables & pex for aft deck washdown / shower... maybe below the fuel tank!

You would think there would be. The Pilot 34 that I have has two runs for wires, cables, water lines, waste hose. Starboard side over the tank, Port side over the tank. There is a solid bulkhead just forward of the fuel tank. With no pass throughs to my knowledge. Reason for me posting this thread. I used a bore scope under the tank and found a dead end. This boat has 4 stringers that run fore and aft. I thought that there would be water drainage to flow fore and aft. Not the case, the bulkhead is glassed around the stringers and to the hull. If you knock on the hull from the outside you know this bulkhead is structural. The boat is built like a tank!

 

[DennisB1]

wkearney99's post demonstrates why using a heat exchange to isolate the engine coolant from the hot water tank coolant supply is important. A circulating pump and a expansion tank on the hot water side is required to move hot water to the hot water tank heat exchanger. If a fitting or hose breaks you have some isolation between the engine coolant and the hot water coolant.

 

[BB-marine]

wkearney99's post demonstrates why using a heat exchange to isolate the engine coolant from the hot water tank coolant supply is important. A circulating pump and a expansion tank on the hot water side is required to move hot water to the hot water tank heat exchanger. If a fitting or hose breaks you have some isolation between the engine coolant and the hot water coolant.

In full agreement of a type of isolation between the engine and water heater exchanger components. In past boats I installed isolation valves at the engine. The isolation ball valves serve two purposes. (1) If there is a failed component or leak in the system the valves are closed. Fails remain closed until a repair is made. (2) The valves can be closed to control water heater temperature. The engine coolant in my 4LHA STP engines reach 175F when cruising. It takes a few hours for the exchanger in the tank to heat sync and heat the water in the tank to this temperature. When we are cruising and I know we will be anchoring for the evening I would open the valves 1 to 2 hours before we reach our anchorage destination. This helps keep the temperature at a more moderate temperature for showering. It is still hot but closer to the temperature that is reached by using the electric element 140F (still hot!). I have already installed the block valves to the block on one of my engines. Just need to figure out how to get the hoses run. Last year when we cruised I used the electric side to heat the water. It takes about 30 minutes for the thermostat to turn off. This uses about 50 ah of battery or a heavy load on the alternator and solar or a noisy 30 minutes at anchor using the generator. There have been several comments about the hazards of this system (exchanger.) I agree with the thoughts. I believe many engine manufacturers do too. There are many things we do while cruising that have consequences. Know your boat and its equipment take caution when using equipment that has consequences. Don't get complacent.

 

[Tonic1]

I was performing some unrelated work in the engine room yesterday and made a few observations. The waste hose from the head as well as a cold water supply to the wash down pump run along the port side about a foot above the shelf outboard of the port engine. These obviously originate in the head and extend into the ER. I also saw the wire I fished thru from the area outboard of the head fixture, going from the waste tank gage to the tank, so that is another possible route for HWH hoses.

The most interesting observation was a red pex tubing with a loose fitting cap on it that just terminated in the vicinity of the head exhaust fat onto the port side as well. It appeared to be for a potential option of either a hot supply yo a deck shower, or the purpose you desire. After spending an hour in the ER doing the work I needed, I lacked the desire to trace it forward.

As to my previous post regarding trying to follow the route of the AC raw water supply, my raw water pump is under the fuel tank and just to starboard of the centerline. The water line runs under the tank and into the rear seat of the dinette. From there the duct runs behind the center seat back of the dinette forward to the v berth. It should be relatively easy to follow that route to the WH and pump area in the forward dinette seat area.

 

[Steve DAntonio]

As an aside, if your water heater's heat exchanger is above the level of the coolant pressure cap on the engine, plumbing the engine coolant to the water heater will require the addition of a remote expansion tank whose pressure cap is above the level of the WH's heat exchanger. This might be why MS didn't plumb the WH to an engine.

Hoses used for this run can be "heater" hose at a minimum, however, I'd recommend SEA J2006 wet exhaust hose, it is far more durable, and include isolation valves at the engine connection points. A failure of this hose will lead to a loss of coolant and overheating.

More information here https://stevedmarineconsulting.com/water-heater-primer/

 

[Sleeping Bear]

If the twin is similar to our single, you should be able to run hoses up the port side behind the wall in the head, then under the sink, and across to the tank, Pretty round about but may also be doable on the stbd side.

Our single has the hwt aft in the engine room, and up the port side is where the plumbing goes to the galley and head over the top of the fuel tank.

 

[BB-marine]

As an aside, if your water heater's heat exchanger is above the level of the coolant pressure cap on the engine, plumbing the engine coolant to the water heater will require the addition of a remote expansion tank whose pressure cap is above the level of the WH's heat exchanger. This might be why MS didn't plumb the WH to an engine.

Hoses used for this run can be "heater" hose at a minimum, however, I'd recommend SEA J2006 wet exhaust hose, it is far more durable, and include isolation valves at the engine connection points. A failure of this hose will lead to a loss of coolant and overheating.

More information here https://stevedmarineconsulting.com/water-heater-primer/

Great information to consider. I was not aware of heater elevation requirements. The water heater is lower than the engine's coolant pressure cap. I purchased two isolation valves from Mack boring that are specific to Yanmar 4LHA engines. Core plugs are removed from the block and valves installed in place. The hose choice was of 3/4" ID water heater hose from MPI Marine Products International, part number 132-0340. 200 psi rated max operating temperture 210F ( operating temperature of my engines is 175F at WOT Max temperature is 180F. I contemplated using exhaust hose for the application but felt that it would be hard to handle making the run forward. That stuff is stiff! Plus it is pricy. I will need about 25' for suction and discharge hoses. If I move the heater into the engine compartment I will use the J2006 hose it will be a short easy run. On a side note I reference many of your articles when working on boats. Great information. Thank you.

 

[BB-marine]

If the twin is similar to our single, you should be able to run hoses up the port side behind the wall in the head, then under the sink, and across to the tank, Pretty round about but may also be doable on the stbd side.

Our single has the hwt aft in the engine room, and up the port side is where the plumbing goes to the galley and head over the top of the fuel tank.

Your plumbing is my plan B. I have followed the plumbing route using port side. it is a bit tight because I have to go over the tank but doable. It is an easier run for exchanger hoses but requires plumbing changes. Thank you.

 

[Steve DAntonio]

Great information to consider. I was not aware of heater elevation requirements. The water heater is lower than the engine's coolant pressure cap. I purchased two isolation valves from Mack boring that are specific to Yanmar 4LHA engines. Core plugs are removed from the block and valves installed in place. The hose choice was of 3/4" ID water heater hose from MPI Marine Products International, part number 132-0340. 200 psi rated max operating temperture 210F ( operating temperature of my engines is 175F at WOT Max temperature is 180F. I contemplated using exhaust hose for the application but felt that it would be hard to handle making the run forward. That stuff is stiff! Plus it is pricy. I will need about 25' for suction and discharge hoses. If I move the heater into the engine compartment I will use the J2006 hose it will be a short easy run. On a side note I reference many of your articles when working on boats. Great information. Thank you.

The "Heater Hose" is technically compliant and roughly the same as the hose used on the engine's closed cooling system, just be cautious about kinking, crushing and chafe, it is not terribly durable.

 

[LongJohn]

My water heater is under the cockpit, about 12 feet from the engine ports. The engine water pump would not move the water through hoses at anything under WOT. I installed isolation valves and a small 12v solar water heater pump wired to the ignition circuit to move the hot engine coolant to the water heater.

 

[Duetto]

we don't have the engine supplying the water heater on our p34, but we do on our other boat. on the other boat, the water heater is roughly in the same location and we get lots of engine hot water even if we're just moving along at 7 knts. if you're not getting supply to the heater, i'd look at where you're tapping in to the pump.

 

[Newtrawlerowner]

I have a 34' 2002 pilot. The hot water heater is located under the forward Dinette seat. Mainship did not utilize the tank het exchanger. The only resource for hot water is 120V power. We like to anchor more than stay at marinas. I'm not a fan of cold showers. We did the Loop last year with this configuration. I do have solar (600W) and I do have a 3000W inverter. Twin engines that can help with battery charging while under way. Our resource last year for hot water was while running with engines and solar with good output. Turn the water heater on. This uses about 70amps. A lot of 12V dc power. Between the 50 amp alternator that puts out about 35amps and the solar controller which averages 35 amps when in bulk charge we could maintain battery Voltage but barely. We have a refrigerator \, freezer, electronics ...... all using amps too. This method worked but it is not efficient. We do not have a generator installed. We do carry a 2200 watt Honda that will power the hot water heater but I'm not a fan of using it when we are underway or if the anchorage has a number of boats anchored. I'm do not like running it because of noise. The efficient way to have hot water is to use the engine closed cooling and the the hot water tank heat exchanger. The issue I am having is finding a path to run the hoses. Mainship build has solid bulkheads glassed to the hull so passage forward is limited and the areas of access seemed to be used. This is a twin engine model so the 250 gallon fuel tank spans the full beam of the boat forward of the engines. If you have this model twin engine and have closed cool water hoses going to the water heater can you advise me as to where the hose runs are? Thank you.

I have a MS 400 and I DID run heater hoses to the water heater heat exchanger. Your arguments matched mine. I did NOT want to run the generator for hot water at the end of the day.
I had a fitting made for the return pipe on the engine cooling system, tapped into the thermostat housing (a threaded hole was there) and ran the hoses through a bulkhead. I did have to make 2 holes using a hole saw. I also installed 2 shut off valves, one on each hose in the engine compartment in case of a water heater leak. Great idea if you can overcome the obstacles.
Good Luck!!!!