Ford Lehmans

Hi everyone. I have a 44 foot marine trader. I am trying to find a piping schematic to tie in 3 hot water bus heaters and 1 hot water tank to twin Ford 120 lehmanns so that either engine or both can heat the boat and hot water.

Greetings,
Welcome aboard.

Captain DS said:

Hi everyone. I have a 44 foot marine trader. I am trying to find a piping schematic to tie in 3 hot water bus heaters and 1 hot water tank to twin Ford 120 lehmanns so that either engine or both can heat the boat and hot water.

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It sounds like you do not have a water heater now in-line? Call American Diesel if your manual doesn't show the loop for your water heater, then add the bus heaters in line so they are a continuous circuit. Make sure the bus heaters are lower than the fill on the coolant system or you'll have air trapped in the loop. If you mount the heaters higher than the engine, you'll need an expansion tank so you can bleed the air from the system. Look at Sure Marine's web site in Seattle. They have the expansion tanks.

You may not be able to run all 3 heaters full on if are running at low rpms on your Lehman (s). The heaters take a lot of heat from the engine so watch your running temp on the engine (s). At higher rpms you should be fine.


I'd just plump the water heater from one engine. KISS

Trying to heat from 1, 2 or both engines complicates the plumbing significantly. You will need a number of valves or a three way valve and some check valves to make sure that one engine can't flow back to the other. Even still bleeding and filling with antifreeze will be a real complication.

So I would follow Larry's suggestion above to KISS. Or maybe run the water heater and one bus heater off of one engine and the other two heaters off of the other engine and keep the plumbing entirely separate.

David