Tuning New Sprint Cat

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B

BradV

Well-Known Member
Joined
Dec 21, 2003
Messages
114
Yesterday had my maiden voyage with the CMB1.0 SprintCat. All went well apart from some tuning difficulties.

Building took longer than planned but I ended up with an awesome paint job by a professional auto painter in 2 pack polyurethane, will post pics later.

This is my first time owning a motor with remote needle and I found it would idle well, but opening the throttle caused it to stall repeatedly. I'm guessing I'm still on the rich side - set the CMB needle between 2-3 turns on 40% nitro.

Are they normally this fussy to tune? I got the feeling with a big dose of revs and a throw into the water it would have taken off, but I didn't really want to do that with a new motor.

Any idea men on where to start the needle?
 
an new engine??? :eek: Then I wouldn't open the throttle toooooooo much, stay on the rich side and cruise around for some laps . <_<

Is the diameter of your fuel-tube sufficient to feed this thirsty baby when you start to rev it up? :rolleyes:
 
Saugling said:
an new engine???  :eek:   Then I wouldn't open the throttle toooooooo much, stay on the rich side and cruise around for some laps .  <_<
Is the diameter of your fuel-tube sufficient to feed this thirsty baby when you start to rev it up?  :rolleyes:

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I'm gathering it's still on the rich side, have some smoke and oil residue in the pipe.

Yeah I went to 5/32 size pipe on all the fuel fittings. Prop size is conservative at this stage with an X462.

It will work out fine I'm sure, this first time out I had no-one to help me so a bit difficult launching the boat and on the throttle at the same time.
 
I dont know where the pipe is on that boat, but when launching make sure the pipe doesnt go in the water or it may shut it off, it did with my nitro hammer anyways. Or even if watergets in the carb it will sputter and die.

Phil :unsure: :blink: <_<
 
G'Day, I have the same boat combo. It has taken about 6-8 liters of 50% and the motor is just comming on song. It sounds like you are to lean, you may also not be getting enough cooling. When the big CMB's get hot or lean they just stop, be careful not to do this to many times as the liner can only take so much. Be sure for the first couple of tanks you have plenty of smoke out the back of the pipe. When launching the boat, throw it in and give it left rudder straight away. This will allow you to keep on the throtle with out flipping on touch down. I found a X460/3 worked well for run in and I now only run a X465 with a little help. Hope some of this helps, as I love the way these hulls run when they come on song.

Cheers Nigel.
 
Thanks Nigel, some good tips there. Fairly sure I'm not too lean because I checked the engine temp repeatedly and it was barely warm. I'm running 2 separate cooling circuits all with oversize fittings.

Do you know if the 462/2 prop (that I'm running in on) is easier or harder to push than the 460/3 blader?

Other thing I have been thinking is plug heat rating, so I will do a few changes there also.
 
I feel the X460/3 gives less torque steer than the 2 blage. I have found that mine will pull anything up to a 472 but it does loose RPM, I feel the 65mm Dia is about as big as i'd go to be very quick. I ran today with a pipe length of 31.5cm and a X465 with a little extra pitch and it was really smoking. I tried a H48 the other day in the rough and it kept the nose down well but was very tricky to judge.
 
Thanks Nigel. My pipe length is 33cm on CMB's non-muffled pipe so I'll leave it like that for a while yet, but I might try the 3 blade next.

Do you happen to know how many turns you have the mixture control set at, assuming it is CMB's remote needle same as mine.

Cheers
 
I removed the CMB mixture and run a K remote mixture on a 3rd chanel.

Do you happen to know how many turns you have the mixture control set at, assuming it is CMB's remote needle same as mine.

Cheers

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I removed the CMB mixture and run a K remote mixture on a 3rd chanel. I se you are in perth, are you coming over for the nationals on the Golg Coast at the end of the year?

I have tried to attach a pic of my cat.

Cheers Nigel.
 
I removed the CMB mixture and run a K remote mixture on a 3rd chanel. I see you are in Perth, are you coming over for the nationals on the Gold Coast at the end of the year?

I have tried to attach a pic of my cat.

Cheers Nigel.
 
No picture came thru Nigel. Needle is set at 2 turns, tried between 2 and 3 turns. Less than that and it screamed at idle so was obviously lean.

No plans to get to the Nationals at this stage, but anythings possible!
 
Sorry I do not know how to send a pic on here. A remote needle is by far the easiest way to go, grat to be able to make changes on the go. Are you running a hopper tank or just a main tank?
 
One of the best ways to kill the big CMBs is to run too lean. This is a very common mistake often paired with over cooling. You want to run very rich then reduce the cooling. This way you get plenty of oil in the engine (good), the fuel provides a lot of the cooling, finally more fuel burning in the combustion chamber means more power.

I work on the idea that too rich makes the boat a little slow, too lean makes the engine manufacturers better off.

Brian
 

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