Merc 7.4 MPI cooling system

[cwms]

Looked at a boat the other day with Merc 7.4 MPI's.
While looking at the cooling system, I see hoses coming off the heat exchanger and connecting straight to the manifolds. That tells me it is a 1/2 FWC system where the manifolds are not part of the FWC system. Am I correct on this?

If it was a full system, whouldn't the hoses go straight to the risers/elbows?

 

[Sandy]

That sounds correct if the RW hoses are going to the ex. manifold not to the risers/elbows..

( bottom diagram):
https://www.perfprotech.com/blog/articles/fresh-water-cooling-full-system

I could never see the rationale for marinizers to offer 1/2 FWC systems as it cost so very little more to make that a "Full" system and "Full" saves so much money, time and lifting weight during preventative maintenance replacements . That said, the 1/2 system could also be a price negotiating leverage feature.

The 1/2 system would not appeal to me for SW use.

 

[Gregory S]

My 7.4s are full FWC. I'm having a hard time picturing them, but doesn't antifreeze have to get from the manifolds to the FW side of the exchanger? The raw water hoses from the exchanger go to exhaust elbows.

 

[GregR]

Mine were full system as well on the 1995 Sea Ray with the Jasper remans. I had these added when I bought the boat. I wish I could remember the hose configuration. Maybe try turning the drain plug at the bottom and see if raw water or antifreeze comes out?

 

[jtybt15]

Everybody has it right. You have to check to make sure what hose has what liquid. Fresh water/Anti-freeze is in the tubes inside the heat exchanger. There are probably differences between manufactures as far as hose routing goes. checking their web sites will probably help.