Logo

2000 Mercruiser 350 mpi with closed loop system, proper connection for hot water heater

Rolling Spirits

New member
I have a 2000 310 SeaRay Sundancer with twin 350 mpi closed loop cooling and want to hook up my heat exchanger on my hot water heater. Where is the proper connection for output and return line from the heater. I've got a mercruiser 22-72932a1 HOT WATER KIT, but the instructions do not show my 350 mpi with closed loop.
 
if your kit has the 1.5" T (with the 5/8" takeoff), its probably not for your vintage MPI.....that said, it will probably work....there's nothing specific about the MPI aspects when it comes to adding the heater connections. Most people just plumb the heater into the bypass hose on top of the circulating pump....
 
Whether MPI, TBI or Carburetor, your coolant supply will be from just up-stream from the actual thermostat location.
NOTE: this must be up-stream of the thermostat!

Your coolant return will be the Starboard-most port on the engine circulating pump (some call this a "water pump").


The engine's circulating pump charges the block/heads with coolant.
The thermostat holds back coolant creating mild Positive pressure up-stream of the thermostat.

The engine's circulating pump port provides a mild Negative pressure.

In order to create good flow to/from a WH or CH, we need this mild pressure differential between these two areas.
No other ports will work as effectively.


Here is an example ONLY of the supply and return ports.
(your MPI manifold may be slightly different)



MPI WH or CH coolant path.jpg
 
Last edited:
if your kit has the 1.5" T (with the 5/8" takeoff), its probably not for your vintage MPI.....that said, it will probably work....there's nothing specific about the MPI aspects when it comes to adding the heater connections. Most people just plumb the heater into the bypass hose on top of the circulating pump....


Thank you so much for all your help....I just couldn't get my head wrapped around the closed loop and between you and RicardoMarine, I think I've got it figured out......so much appreciate you two fine individuals taking the time to help me out!!!
 
Thanks so much for your help and advise.....I headed to the engine compartment now and feel the confidence to tackle this project.......again thank you for taking the time to respond back!!
 
Back
Top