Hi Guys

Just trying to sort my Evo out in minimal time.
Setup is a Jesse James 41" cat, s254 Evo with 929 carb, QD Hotpipe with 3 inch coupler (measuring the coupler from end to end) Im not quite on pipe properly yet and need to find some more RPM's. Im thinking I should go slightly longer on the pipe as the power is dropping off a little in the corners, shall I try this or lean the HSN slightly (its currently at about 1.2 turns and the LSN is 2.25 turns
Last night I ran a detongued x467, then tried the 1470, hugely different props, but no real difference in speed or RPMS..

Thoughts please

On a STOCK engine, the 3" coupler is IMO too long already.
Understand the longer the exhaust duration becomes (higher timed)LONGER pipes need to be set. Less duration = shorter.

So you want more rpm, need to shorten the pipe .... Engine dogs down in corners ... use less prop or run it shallower

As too H needle, read your plug for color ... make a hot WOT run and shut down quickly. What you are looking for is a med tan to chocolate brown center electrode. Lean or richen H needle to get this ... that will be the sweet spot.

Thanks Scott, what length would you suggest trying so I can make some couplers ?

I was going to try longer as I though that would help it get "on pipe" as it doesn't sound to be really revving like I am used to with my other motors

Having owned that exact Cat and help set up and tune another, props you mention while ok are far from optimum IMO. Best prop hands down on that hull and a lot of Cats in general is the 7016/2 with round tips ( Bob Austin mod #440 )
First off make sure where your H needle is and get engine mixture near the sweet spot if not ? already there.
Set bottom of your strut @ 5/16 - 3/8" above sponsons ride surface for starters.
Pipe coupler deal with last, let see if you can get engine to free up and make some RPM where your at. Likely coupler won't need to go any shorter than @ 2 5/8" to get good rpm once you unload the engine with a propper strut heigth and correct prop.

Scott

Many thanks for that Scott, I will make some changes tonight and test the boat after work tomorrow!

Thanks!