97 Challenger 1800 - RPM Issue

[TheCabralFamily]

Well here's my story....

Bought a 97 Challenger, overall good condition back in June. It has been a project ever since. I now have a new PS Engine, and it runs strong. The SB side engine runs good but when I get on the throttle it goes up to full (7200) RPM, and if left at full the boat runs amazing, however when I let off the throttle even a little bit it drops to 4500 RPM and stays there, until I drop the throttle below a certain point. I don't have any throttle control from 4500 RPM to 7200 RPM. The carbs have been rebuilt (OEM Parts), fuel lines are new and pick up has been replaced as well. New Plugs, and matching good compression. I completely stumped here. Thank You

 

[nisjeep]

Did you pry off the plastic plugs on the high screw on the carbs? Other than the high setting it might be sticky raves.

 

[Lumps]

My tach use to get stuck when it was less then full throttle. Are you sure it's not your gauge?

 

[TheCabralFamily]

Here's a Long Overdue update! I finally had the chance to work on it over Spring Break. I replaced both Rave Valves, old ones were very blackened but otherwise no visable damage. The one engine (SB) now tops off at 5000rpm though. The weird part is, when I get on it it goes to full 7200 RPM, and once the boat planes it drops right down to 5000 rpm and that's all I get. I have not located the "High Speed Screw" on the carbs, and even had trouble looking for an image online....any help wold be greatly appreciated...Thank You

 

[glenn2726]

Hey TheCabralFamily, I'm new here and just purchased a 97 Challenger 1800 twin rotax also...haven't ran across this problem....yet...so you are saying that the rpms drop back once it gets on plane if you back off the throttle? Have you tried swapping carbs from one engine to the other to see if there is any change? Seems like there could be a dead spot in the carbs where you're not getting enough fuel until you punch it. Good luck..hope you get her in the water soon...

 

[snikwad003]

Rave issues won't stop the engine from reving all the way up, the raves change the power band. Your plug caps unscrew off the wires, trim them back a 1/4 inch or so and screw them back on. It sounds like a fuel issue tho and if your running lean due to the carbs, fuel selector, sucking air somewhere or other fuel related things you can melt your motor down. Check that hoses are tight. The fuel valves can be and issue if they are twisted in their slot and you are not clicking it to the right spot. There is other stuff too I'm just brainstorming