roughneck793

Think a tuned pipe for a .18 is too small to run on a .21 engine?

misshydro

yep...you need a 3.5 tune pipe for your.21 I'd tried that three years ago .Try a.18 tune pipe on a.21 and it did hit the pipe/boost didnt kick in.[>:]

Dan S

before I say yes or no,

what pipe are we talking about?

Dan.

Ron Olson

My Feedback: (1)

I'm with Dan on this one as it does depend on what pipe you're typing about.
Let's say that it's a Cooper .15-.18 pipe just for one to talk about. That one is basically what was once known as an Irwin .21 short pipe. Cooper took over Jim Irwin's inboard pipe business while he kept the OB part going. The 21-S pipe was a rare one that worked fantastically on everything from a .12 to a .21. Rod Geraghty found that out while trying to find a hot pipe for an "A" hydro record setting boat.
Now if you're talking about which I am presuming that you are, then it can be a toss-up. It can also depend on what engine that you want to use it with.
There's only one way to find out but set the pipe up so that you can adjust it through a good range of lengths.

roughneck793

Not sure of the brand, A friend of mine has it and he said it came off a a .18 The motor is a k&b 3.5 inboard ( i still can't find a black carb for). The pipe is 8 1/2 long and 1 1/4 at widest point.

Ron Olson

My Feedback: (1)

Go for a gold carb instead of the black one. The black is a good carb if that's what you find but the gold one has a slightly larger bore.
If you don't know what the pipe is, throw in a shot of it if you can.