Is it possible/practical to run an 18' cataraft with a 25 horse long shaft prop up and down the Copper River, putting in at Chitina, and heading down the Copper from there? Or is that jet boat territory? Thanks.
More than doable
You can and people do run 14ft Otters, 16 and 18ft Cats and just about any other type of reliable raft / inflatable down from Chitna to the Million Dollar Bridge.
Mind you if you plan on hunting you better check the regs there is motor restrictions from about 8 miles up from Chitna down a ways.
Excellent fishing in certain location and outstanding adventure.
Not sure how much upstream you will be able to do. The current runs about 7 mph and the canyon may be a bit faster. Can your setup make any time in that kind of current? Like BlueMoose says, lots of people float down.
NOT really -
Heading up river for any longer distance/duration in an 18' cat pushed by a 25 hp outboard is not a worthwhile venture. Traveling downriver bucking the head wind trend... sure enough... just not going up river for any good progress unless you are nearly unloaded.
copper cataraft w/25 hp
I agree with the last post entirely. I have done a bit of experimenting with powered cats and you really have a lot of variables. For one thing, if you have a rockered cat, like an Aire for example, the rocker on the rear of the tube makes the bow kick up more severely under higher power. Tubes that are straighter have less tendencies for this. Weight and balance become real issues. Here is a prime example, I have watched two different powered cats dipnetting on the Kenai from my powerboat. Same boats, same loads. One had an 8 hp motor, one had a 25 hp motor. The 25 hp could beat the 8 hp, but not by very much. The 8 hp stayed level, it wasn't overpowered. It used the low profile of the cat tubes to glide easilt through the water. The 25 hp tried to "get on step". It would sink in the rear and the spray was terrible. Containing this with cats is always a problem. The people in the boat would have to practically hang off of the front to try and equalize the boat. And in the end they were barely faster than the guy with the 8 hp. Inflatable raft just aren't designed for getting "on step". And that is what you wil need to do to be effective on the Copper. The mouth of the Kenai is childs play compared to that place.