Questions about Clutch, Driveshaft, Friction...
 

I recently wound up with a gas boat from a buddy of mine. He had overheating issues. I've been running the boat briefly to try and resolve, and I've made progress. I rerouted the cooling lines so the water jacket on the head has a direct shot from the pick ups on the rudder. I'm about to reroute the lines for the exhaust as well (currently using a hull pickup that resembles a jet skit inlet). It flows when I spray it with a hose to simulate, but I believe it needs a bit more.

My questions though, are about the Clutch and Drive shaft. It doesn't seem very fast, like maybe 30mph. Most of the vids I watch show similar boats going much faster. Could I be losing much power with the clutch? It seems to be integrated with the engine (like it was on there when they removed it from whatever lawn device it came from). Does it make sense to try and remove it?

The Drive shaft seems free, no apparent issues. Should I remove and grease it up anyway?

Personally I'm not a fan of clutches. They add weight and one more thing to go wrong. I've never used one and zero plans of trying one unless I built a huge boat with twin engines.
I just saw on the RCU home page where the author put a clutch in a AC Model Boats Blast Cat 40. I had one and that one of the last boats I'd do it to. He also didn't put in a vacuum or any other type of water pump, a bad move as you need water flowing. No water flows if you're idling on the water.

Flex shaft should be cleaned and regreased after each trip to the lake. While clean - check it over for broken strands, points of wear, or other items that may appear out of ordinary. Realistically a clutch or old grease on your driveline is not likely to be the cause of speed loss.
WHat kind of boat is it. Any pics or better yet video in action?

30mph is not a bad speed for a gasser - though no doubt there is more speed available with a few tweeks or adjustments - and the correct prop can do wonders - just depends on what you have and how it is currently set up.