Power/RPM Loss When Hot

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Tudorc

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I have a 97 Challenger with single 787. When the engine is hot (after 10mins+ use at high revs/WOT), I can’t get the boat onto a plane again and the RPMs stick at 5000. If/when I can get it to plane in these circumstances, the RPMs are 1000-1500 lower at normal WOT RPMs (6800ish normally) but the RPMs go intermittently up and down slightly (500rpms up and down).
The boat was serviced a week ago, ran great for 5 days and then this problem started. Compression is/was 125psi. The carbs were rebuilt. I pulled and cleaned the RAVEs again, replaced the plugs and inline fuel filter.
Again, when the engine is cold, it gets onto a plane fast. It will rev to 7000 in reverse all the time.
It’s also pretty tough to start when warm and it has been sitting for a few minutes... not sure if this related.
Any ideas?
 
Have you checked the engine to see how hot it is? (I like an IR temp gun) But just putting your hand in the water stream from the pee hole will tell you how hot it is. (Just don't burn yourself) Along those lines... is the buzzer OK?
 
So I think I’ve made some progress. I tinkered with the idle (set it to 1500 rpm), adjusted low speed and high speed screws out a quarter turn (it was running a bit lean all the way through) and then adjusted the RAVE screws all the way down. I think the RAVEs were opening too early. Either way, this combination of changes has it pushing past the 5k RPMs and planing nicely (with 1/2 tank of gas and only one passenger anyway).
Engine temperature is fine. Hopefully this’ll be a permanent fix and it’ll work better with more of a load (people/tube etc).
 
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