Trojan Boat Forum

My 1971 F26 has a water flow path like the chart below except because it is a V drive the water to the transmission oil cooler comes out of the exhaust manifold directly beneath where it enters the exhaust manifold.



What does the inside of the exhaust manifold look like? Does the entering water go directly out the hose below or does it go throughout the manifold before exiting? I'm wondering how hot the water going to the transmission oil cooler is. Thanks for the info.

Greetings Dog House!

The water does pass through the manifold, but the temp is normally around 110-150 degrees F. Coolant in marine engines never gets very hot, unless you're idling with a bad impeller that won't draw in water well at low RPM. I have the same setup, and the water is barely warm after it exits the exhaust, but she has fresh impellers each season. I'm also on Lake Superior where the water rarely gets close to 70 degrees F...

Basically, inside the manifold, there are large channels for your exhaust with smaller channels around them where the coolant exits. The water enters the manifolds separate from the exhaust, and once it exits the manifolds, it combines right before the muffler. That's the best I can explain, but if you google-search them and also look at the gaskets I think you'll see what I mean. Fairly straight forward in design.

Cheers and happy boating!

Thanks for the info.

Dog House,
Mine used to be set up as yours. I have since replaced the engine and made it FWC and the exhaust manifolds are FWC as well. The oil cooler is now cooled directly after the heat exchanger.

One think you should periodically check with your setup is for rust flakes/scale from the innards of the exhaust manifolds that builds up in the oil cooler. Over time the inside of the exhaust manifolds rust and flake, these flakes are big enough to block the passages of the oil cooler if unchecked. With my old set up, I would remove the hose on the inlet side of the oil cooler and stick a small magnetic pick up in the oil cooler and it would pick up the flakes, this would also let me know if the manifolds are starting to deteriorate, after that I would also back flush the oil cooler with a garden hose just to make sure I got everything out.

Thanks for the advice. I never thought of the manifolds sending debris to the cooler but it makes perfect sense. Has anyone reconfigured the flow path to pass through the V drive and transmission fluid cooler first, then to the manifolds, and then to the second stage of the water pump? Given the debris issue, I might look into reconfiguring my current setup.

I don't think it warrants changing everything. I'd just keep an eye on it and flush it out every few months.