Looking for some suggestions. 1989 Formula 292 SR1 Twin 502 Crate motors.
I have a slight stumble just as I get on plane.
Have had the problem since I repowered some time ago.
Twin 502 Crate motors, gil exhaust, std ignition, MR 43T plugs. Holley dual feed 750 CFM Carb. timing good, carb adjustment seems fine, idle nice. Plugs look good.
Boat runs extremely well once up on plane, throttle responce is real good, I can keep the boat on plane at 2400 rpm's, wide open 4900 to 5000 everything seems right on the money EXCEPT THE SLIGHT STUMBLE???
The boat runs so well I have actually left it alone and not played with it.
Any ideas ??
Thank You in advance for the reply !
Brian

Accelerator pump? If it occurs right when you open the throttle, and then goes away, I would check the adjustment for the pump to make sure it is actuating soon enough to cover up the lean spot that is caused by the sudden opening of the throttle. You may need a different accel pump cam, and/or possibly a bigger pump, especially if this is an automotive carb.

Definitely could be accelerator pump issue, or a leaking/blown/too late power valve. Crate engines probably fine with 6.5's.

Hey PROWERNCH, when you say 6.5 precisely what are you referring to ?
I ran the boat all day yesterday , ran absolutely flawlessly except the stumble , just as you start throttling to get on plane pretty signifigant stumble. at 1250 rpm's then it is gone once you get past 1250 both motors same exact carbs and settings
?
??
Thank u in advance for the reply.
Brian

He's talking about the size of the power valve (how much vacuum it takes to open it). Heres some pics for you sir. First two are of the power valves (and where they are located), and the third is of the accelerator pump.

Heres a better explanation: http://www.holley.com/data/TechServi...wer_valves.pdf