My ASP .12 engine is finally in my boat now and I took it down today to test the watercooling system (which worked, thank god). However, I had to adjust the idle to about 1/4 throttle just to keep the engine running in the water and when I went to 1/2 or WOT there was little increase in power and barely any increase in rpm. On land with the engine being cooled by a water tank, although with no load, the engine revved up with even just a blip of the throttle. If I hold the throttle open with the boat in the water the engine eventually stalls. Has anyone any ideas as to what is going on here? I tried both richening and leaning the mixture - all that happened was the engine stalled.
I'm running 20% oil (all castor), 10% nitro, 35mm waterscrew, MVVS throttle pipe.
Anyone any ideas? Thanks,

most boat watercooling systems need the boat to be moving, is yours like this? If so, your engine is overheating when you are doing test runs in the watertank.

It sounds like your low end is too rich, and the top end mixture way too lean.

Rob:

When the engine comes under load (goes in the water) it has to be a LOT richer than running with no load. Set the HS needle to a blubbery rich setting and give the boat a good shove when you launch it. Work from there.

Bill.

I've been playing around with it in the river - it's better now (set much richer) but not perfect - only can get about 3/4 throttle before it bogs down again. There's only the one mixture needle - no bottom end setting. BTW, the cooling system works at idle (just!) so thats not a problem.
Even at 3/4 throttle, the boat moves like there's no tomorrow! It doesn't look like a speedboat but it certainly goes very quickly. Looks like 2 months of hard work has created something worthy. It's still not perfect though (there's a split in the keel that needs solving with some fibre-glass and resin - the hull was leaking earlier!
I'll post some pictures when it's all done - so far, so good, though!