Mac .21 outboard carb questions ..& whats a suitable tunnel hull for this?

[ian thompson]

Hi all, I just bought a Mac .21 on a K&B lower. The carb has a needle on the moving part of the barrel at WOT the needle is nowhere near the jet.Am I correct in thinking this needle is for low speed /midrange & I will need a remote needle for WOT ?

If so is it worth getting one that can be adjusted with a servo? Any suggestions to source a suitable needle?

Any suggestions for a suitable hull for this outboard?

Thanks for your time

Ian

 

[Eric Bourlet]

What Carb is it. I have several Mac.21 motors the carb that came on it has no needle. If you have not used a remote controlled needle before I would recommend against it. You would be better off using a manual needle to learn to tune . Its very easy to get greedy with a remote controlled needle and go lean.

I run that power head on a Lynx but I use an OS PTO in that motor so it fits the OS lower. What pipe do you run on it?

 

[ian thompson]

Hi Eric,Thanks for taking the time to respond. I`m not sure what carb it is or what pipe. Have attached some pics. You can see how the needle is away from the jet at WOT.. I`m new to boating but not new to model engines. I know the damage a lean run can cause..If you are very lucky its only a plug..



Ian

 

[Brandon Atwell]

CMB carb, Gadjit pipe.

Truthfully I think that may be a CMB motor with a MAC water jacket. Think the outboard Mac's had black cases and flywheels. I know the outboard waterjackets were black for sure.

If it's a CMB, it would be the RS or short stroke Green head. Still very strong motors regardless.

Edit: Found a picture, definitely a CMB Greenhead with a Mac water jacket.

 

[dave roach]

Ian

The carb is a mac and the pipe is a Gadgit craft.

 

[Brian Sorgente]

Yep. Still a great motor, just not a Mac. Ian you are correct, that's a low speed needle and you'll need some kind of remote needle for wide open throttle. It will go between your tank and the fuel nipple on the carb. I might even be inclined to cut the low speed needle off but that's just a personal preference. Some people love them, I don't really care for them as it's just one more thing to mess with..

Again, personal preference but I would go with a 3rd channel needle setup. As stated before, they can be a little tricky at first but after you get the hang of it, it makes needle adjustments much faster. I wouldn't run an engine without one now. I prefer the OS inflight needle. Don ferret makes a nice needle base for these which I'm sure you can find in the manufacturer for sale section. As for a standard style needle, I used to like the CMB ones, K&B also had one that worked well too.

Hope this helps,

Brian

 

[jaxracer]

Hi all, I just bought a Mac .21 on a K&B lower. The carb has a needle on the moving part of the barrel at WOT the needle is nowhere near the jet.Am I correct in thinking this needle is for low speed /midrange & I will need a remote needle for WOT ?

If so is it worth getting one that can be adjusted with a servo? Any suggestions to source a suitable needle?

Any suggestions for a suitable hull for this outboard?

Thanks for your time

Ian

Ian, my suggestion to you would be to back the low speed needle that's in the carb out as far as it can go without falling out of the carb and then run an inline needle to the carb. Having run CMB 3.5 outboards, that'll save you a lot of headaches. If you're looking for an inline needle, Ron Shaw sells a decent one from Nova Rossi, the OS needles from Tower Hobbies are good as well. If you want to run a needle set up that you can adjust with your radio, Don Ferrette on here sells about the best one I've ever used.

-Mitch

 

[ian thompson]

Hmm ahh well I dont mind really ..I didn`t pay much for it.I dont think the seller knew what he was selling either.Thanks for the help guys..Im now researching inline & inflight needles lol

This should have a bit more oomph than my K&B`s

Ian

 

[ian thompson]

Is this the correct needle assembly? Found this on Tower Hobbies : OS Part# 23882900 ..OS remote needle assembly 21RZ-M ..It says it can be adjusted with a servo but the pic doesn`t show this..

Ian

 

[ian thompson]

Im not doubting you guys but I found these :

Apart from the colour the crankcases appear identical..Is the MAC a copy of the CMB or vice versa?

Now i`m really confused..but happy lol

 

[RonShaw]

Ian,

I keep the remote adjustable needles and three styles of bases in stock at less than Tower prices. Thanks.

http://www.novarossi.us/collections/needle-valves-remote-adjustable-and-needle-bases/products/needle-valves-remote-adjustable

 

[Andy Brown]

Im not doubting you guys but I found these :

post-2144-0-35256100-1418351943.jpg

post-2144-0-45864500-1418351913.jpg

Apart from the colour the crankcases appear identical..Is the MAC a copy of the CMB or vice versa?

Now i`m really confused..but happy lol

The MAC uses the CMB crankcase. All other internal and external parts are pure MAC. The Engine in your pics is using the MAC Off-road buggy crankcase. Someone must have changed it out. The actual MAC Outboard case has the cooling fins turned down to the same diameter as the black water jacket.

Now that I look closer, that is the MAC Buggy engine with an O.B. carb and water jacket and standard flywheel. It is set up for Inboard use.

 

[ian thompson]

Thanks Andy how can I tell if my engine has CMB or MAC internals ? Not that it really matters but I`d like to know lol.. It seems someone has gone to a bit of trouble to mill off the side of the case where MAC or CMB should be then install a MAC water jacket & carb.. Why would anyone bother ?

Is the CMB porting different in the liner? The rod in my engine doesn`t have the groove milled up the centre..also the carb has a needle in the barrel..is this MAC or CMB ?

Cheers

Ian