Closed loop cooling for Suzuki 115

My son runs a tour boat on a river and finds that the mud and/or gravel plugs the coolant circulation system. Has anyone done a modification to do "closed loop cooling" where cooling fluid is circulated through a tube running along the keel exterior.
How do you cut off water from the leg and create a closed loop?
Quite a challenge! Hopefully some genius will have the solution.
Thanks

New one on me. I guess it is possible. You would need some custome made parts to pull it off.

man, you could do this but it will be tough

It seems like it might be easier to install a normal pump on the boat that pushed a decent volume of water to the area around the cooling intake to keep debris from reaching that area. The pump's intake would be higher in the water column, of course.

I don't know how that would work. I can see where you could pump water to the motor but the return side would seem to be the trick.

What he ought to look at is a low water pickup like Bob's Machine Shop makes. Not a nosecone but rather the low water pickup that mounts on the boat's transom.

Basically you drill and tap a hole thru the lower unit into the water passage. You thread in a fitting. A hose connects to that and runs to the water pickup that you mount on the transom. You then plug off all the water intake holes on the lower unit. As the hull moves forward the pickup scoops water up and feeds it into the lower unit.

I have seen some home made versions of this setup and it works really slick. Only downside is you only pump water while moving forward. So if you need to idle alot it probably wouldn't work.

quick question. how does he clean out the blockages in the cooling system when they occur? is it simple or time consuming, and does it ruin his impeller?