Need info - How-To regarding Flow Meter etc.


Help Support Intlwaters:


Well-Known Member
Jan 9, 2004
Hey guys, how do I use a flow meter? I've got a lot of RC Boat equipment I've built over the years and as I approach little less hectic/time consuming lifestyle I'm beginning to get out and actually start playing with the stuff (finally). That said, I've got a substantial Nitro and Gas boat inventory and to be honest I'm not that well experienced in how to tune the nitro stuff. I can get by with my gas toys but the nitro stuff I know demands more insight to get the things to run right, transition nice, pull off the beach and ultimately arrive back to the driver after making a few laps. I'm a "sport" boater with no real desire to race but I own many worthy race-able boats.

My question is this: I've got a couple different types of flow meters one of which (as I recall) is in a big wood case and another one a smaller hand-held version. I need to know how to tune the NITRO engines as far as with the flow-meter and what I need in the trailer to better accommodate that effort?

- Do I need a "weather station" or temp gauge, pressure gauges etc?
- Who makes the best most user friendly flow meters and how do you use them?
- Where do I shim the engines as far as head clearances?
- What nitro content is desired for the various engines i.e. 21's, 45's, 67's, 90/1.0's etc?
- Where do I start on pipe length?

I pretty much own about every type of RC boat and configuration imaginable be it Nitro or Gas with the exception being I don't have a single tunnel hull O/B and I don't own any twins (yet).

I know that's a lot of stuff to crunch on but maybe I can get some feedback and get going on a better "bench" setup prior to heading to the lake.

Nitro hulls in the stable:
20 Sport Hydros
20 Hydros
45 Sport Hydros
45 Hydros
60 Hydros
90 / 1.0 Hydros
20 / 40 / 60 / 90 / 1.0 - Monos
1/8th Scale Hydros
and some sport 60 Hydros
60 / 90 Cats
Hey Kenny Hildreth I need to talk you into another KC trip and I'll buy the eats and drinks cuz goodness knows I could use some of your "Yoda" knowledge on this stuff.

Wasted wages

Well-Known Member
Jan 2, 2006
There's no magic number for each boat or engine. Basically what the box does is give you a baseline number of your needle
 After you have your boat running good.

Take flow meter readings and keep notes!!!

Get a small binder book and keep it with your meter. Keep track of things like
Temps, humidity, air density things like that... then no matter where you go to race you can set your needle to achieve the same flow.

Altitudes change, barometric pressures change etc. The box compensates for some of these changes and gives you a target to shoot for.

Before third channel valves, we used OS needles that had barrels that clicked
when you turned the needle,, if you were lean you might open up the valve 2-3, lean on it a click or two...

Once we would get the boat hauling azz we would flow the needle at .40 inch water column, and record the flow number.
Say it was 6.5 for a .67 picco in a mono.
89 deg. @ 80% RH

Then no matter where I went to race I would reset my needle for 6.5 @ .40 inch water column..

Fire up the boat and throw it in...perfect needle.
I may have to click up or down a click to compensate for ambient or RH change,
But it would be darn close..that's when you start looking at your glow plug coil..

With the advent of remote needles and gas,, flow meters and needle valve settings have become a dying art.
BEST THING I can tell you is keep notes, keep notes, keep notes....

Flow meters are great for checking fuel tanks for flow,, finding clogs, leaks, water lines will be amazed at little differences you can find on fittings and things like that..

Last edited:

Mike Hughes

Well-Known Member
Feb 23, 2003
Pretty much Frank covered it all. It will not get you there. But once you are there it helps to get back to that point. I run 3rd channel needle. So I use mine as a setup tool mostly. Sometime for troubleshooting issues.

Wasted wages

Well-Known Member
Jan 2, 2006
Tom,, I'm sure you have an old needle valve and carb with a low speed needle in it.

Take a hour or so playing with the meter and the needle and carb on the bench...
Flow both. Flow the carb at idle position, mid, and wide open.
Write down some readings, take the needle and carb all apart, I mean pull the low and high speed needles all the way out, clean it all up and then reassemble both, then using the meter and your saved readings, adjust everything back to your settings.

This will give you some insight to how everything relates to using the meter.
Good self teaching time...


Well-Known Member
Oct 25, 2015
who makes a good 3rd channel needle these days?

I like the OS In Flight for 21's and mild 45's, but for modded and high nitro % it's really hard to beat Stu's.
There are some Chinese Stu knock offs online but I know nothing about them first hand.

Have used Ferrette's and KRE bases for the OS and they're excellent pieces. Have a couple of Speedmaster bases but haven't ran them yet.

Hope that affords you some insight.