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Old 22-02-2018, 03:59   #1
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Join Date: Mar 2017
Location: Hudson FL
Boat: 41ft Gulfstar Ketch
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Water heater installation

I have a Perkins 4.108 (ED70058) with the Bowman heat exchanger in my sailboat I am trying to plum for my hot water tank/hot drinking water. Where can I tap into the engine for my out to the heater and the return? Just right of the t-stat housing is my temperature sending unit. The port in the head just behind the t-stat housing and the port aft of that behind the #4 injector on the left side on top of the head are both plugged. I appreciate any help you can give.

Thank you

John L.

“The voice of the sea speaks to the soul.”

― Kate Chopin
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Old 22-02-2018, 04:37   #2
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Re: Water heater installation

Greetings and welcome aboard the CF, John.

Perkins 4-108 Water heater plumbing

Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

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Old 22-02-2018, 04:50   #3
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Re: Water heater installation

I did this job a few months ago on a 4-108. On the foreward block tap where the temp sender is located add a 4" pipe extension and a tee. One side of the tee is for the line to the water heater. The other is for the temp sender. Run the line back to the water heater.
The return line taps to a tee that is after the heat exchanger and before the oil cooler.
There are several posts on the forum with pictures that show this set-up. This provides for hot water generated as soon as the engine heats up and before the thermostat opens.

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Old 22-02-2018, 05:21   #4
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Re: Water heater installation

I’ve got that exact setup and my water heater just gave up and has been leaking hot water into the bilge.
The hot line from the engine runs to a surge tank a little higher than the water heater. This has a radiator cap so you can add antifreeze.
My water heater is mounted in the cockpit lazerette and is higher than the engine, so if you open the cap on the engine, all the coolant in the water heater lines and exchanger drain out by gravity.
I suggest adding ball valves / shutoffs to your coolant and fresh water lines. Makes it nice to not flood your cabin / bilge etc.
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Old 22-02-2018, 13:52   #5
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Re: Water heater installation

I did this a couple of years ago. On the front end of the cylinder head, there are two 1/2" NPT taps in to the water jacket. One is behind the thermostat housing on the port side, the other is on the starboard side. I'm using the plug behind the thermostat for a high water temp alarm, so I decided to go for the plug on the starboard side.

I removed the plug on the starboard side (with great difficulity and uncommon malice) and put a hose barb there. For the other end of the circuit, I but a 'T' in at the starboard side of the block, behind and below the alternator, where the coolant enters (or exits) the block. There is a wrap around copper pipe here that connects the engine block water jacket to the manifold/water tank (with a Bowman type manifold).

I had to cut this copper pipe where it bends back toward the block and put a bronze 'T' assembly there. The T attaches the block hose, the copper pipe and the water heater circuit.

I honestly have no idea which way the coolant flows through the coil in the water heater with my setup. I figured if one end of the circuit was on the head, near the water pump, and the other end was attached at the block, near where coolant enters (or exits) the water tank, then there should be a pressure differential, and that would be enough to ensure flow.

Seems to work fine. I get hot water when the engine runs. I do have to check coolant levels a few times when I drain the system and re-fill. There are a few more places for air pockets to develop, but it eventually all fills up and stabilizes.
S/V Argyle
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