no more rpm after .75 throttle

[anthony_marquart]

What does this mean? Need shorter pipe or too short already? Need smaller prop? Bigger?

 

[brett english]

might be your too lean....when im in the middle of a race and im full throttle and its surging, ill go back to 3/4 throttle and the boat runs faster..hows your plug

look after the run?? if plug looks good prop could have too much diameter

 

[anthony_marquart]

Staying on the rich side all the time now. Plug looks good. It's on the 21 rigger.

Phils hobby shop online just type in the name and look for Phils from Indiana. Odonnell plugs $2.50ea.

 

[bermudadude]

plug too cold

or

carb too big ?

 

[anthony_marquart]

Glenn's carb mod nr21 od blues

 

[Rene Danner]

What pipe?

 

[Grimracer]

To much prop could be it.

grim

 

[DeanJohnson]

Did you check for debris in your needle valve? I had a very similar occurrence this summer, and when I unscrewed the needle I found a small piece of debris causing a slight blockage. I run a filter as well, so I'm not too sure how the debris got there.... But it did.

 

[moparbarn]

Try a hotter plug, getting kinda cool out for blues. i had the same issue with blues in my .21's in the early spring.

 

[anthony_marquart]

S pipe.. NR Hybrid,.. thanks for the input..

 

[shoboat]

Tony,
Need a hotter plug OD-77's forget the sport plugs.
What was the set up?
Propeller?
Cup?
Pitch?

Diameter?
Nitro%? 66%?
Not enough engine temperature most likely, try no water for a few laps?

You will have to richen up a little more with no water.
Let Us Know Please,

Mark Sholund

 

[anthony_marquart]

Sorry for lack of detail,

JAE style rigger

NR Hybrid engine

H7 by mark, can't remember numbers right now

S pipe, at 8in

66% nitro

water flow at 0.050 diameter through head.

Boat will get to max speed real fast, about 68 .. and then go flat about 3/4 throttle. and then no more..

 

[Walt Barney]

Sorry for lack of detail,

JAE style rigger

NR Hybrid engine

H7 by mark, can't remember numbers right now

S pipe, at 8in

66% nitro

water flow at 0.050 diameter through head.

Boat will get to max speed real fast, about 68 .. and then go flat about 3/4 throttle. and then no more..

Cut your water down to .025 I run .020 on about the same set up

Walt Barney

 

[Duck899]

Sorry for lack of detail,

JAE style rigger

NR Hybrid engine

H7 by mark, can't remember numbers right now

S pipe, at 8in

66% nitro

water flow at 0.050 diameter through head.

Boat will get to max speed real fast, about 68 .. and then go flat about 3/4 throttle. and then no more..

shorten the pipe 1/8" at a time

 

[anthony_marquart]

when the pipe is too short,. of course often will not launch. With the JAE style boat they about launch at any pipe length. When shortening pipe should i see speed / rpm increase, then decrease when I get too short?

 

[Brian Sorgente]

If the pipe is too short typically the engine will fall off the pipe in the corner. Does it happen to go FASTER when you let off from full throttle?

Brian

 

[anthony_marquart]

no,.. it stays the same from 3/4 to WOT. Ill be trying more restriction in the water flow.. and hotter plug..

 

[shoboat]

Tony,

Good idea!

Hotter plug

No water

Richer needle

In the off season let me get those propellers measured up so you know

what you are running?

Thanks,

Mark Sholund

 

[Jeff Schindler]

The question is, what do you expect the change to be when opening the carb from 3/4 to open?

Your answer may be you expect to get less air restriction allowing higher air & fuel flow.

What if the engine is already at max flow rate at 3/4 throttle?

Do you need more crank volume? More intake timing? More prop load? Less nitro? to get more flow?

Sorry I have more questions than answers, but I am stuck around 68 mph as well.

 

[anthony_marquart]

Jeff. You had to ask the hard questions didn't you,,! I don't know those answers