Installing a water heater in a 87 268

Ottawamerc

Ottawamerc

Member
Mar 23, 2016
74
Kemptville
Boat Info
1987 model on a Karavan tri axle trailer pulled by a 2016 F250 7.2L XLT
Engines
7.4 Mercruiser
Hello All

I'm planning on installing a water heater in my boat this spring. It did have one before but the PO removed it and bypassed the lines, also I have since installed a 454 to replace the too small 350. The new 454 doesn't have any spots that I know of to connect the heater lines? If anyone has any pics of theirs or where to connect I would really appreciate it!

Scott
 
Oh sorry yeah its a fresh water system.
 
On my 454 near the thermostat are some plugs. I had a heater installed once using them. Not on boat or near it. Should be there in 2 weeks and will look. Have no pictures of that area.
 
Well I just tried it today on muffs in my lane way and it didn't circulate well through my heater. I connected my engine cooling lines at the thermostat housing and the water pump housing, there was 1/2" pipe thread connections there. Might need water trials before my final decision on this connection locations.
 
My starboard engine feeds a cabin heater blower under the dinette table. There's a send port on the top of the thermostat housing. The return is in a port on the intake manifold.

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My port engine feeds my water heater. The send line is on top of the thermostat housing and I don't recall where the return is at this time. I believe it's a t-junction under the exchanger tank.

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Either way, your hot coolant isn't going to flow unless the thermostat is open, so you have to be up to temp. You also will need to bleed the system of air to ensure proper flow. Ideally, the hot water heater will be below the level of the upper portion of the T-stat housing. Not necessary, but helps the flow.
 
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