mac 21/ cmb 21 prices

[k&b guy]

just compared prices. mac @ phils hobby shop 234.99. cmb @hobby supplies (aust.) 384.75. (converted). cmb better eng? or ???????? CARTER

 

[shoboat]

Carter,

Which CMB outboard LS or RS? It does matter. They are both good motors, and both need an after market lower

unit you know?

Good Luck,

Mark Sholund

 

[k&b guy]

mark, the cmb is a rs. CARTER

 

[Jerry Wyss]

Talk to Tim Duggan about the RS, would be a great unbiased opinion. I know hes ran a few as well as

modifying some. He should be back on friday,, I know some about the Mac,, my pal "Jim" has one on a

OS lower that I made up for him. I'm completely sure they are a tough engine for being in Jim's hands

for several months now :lol: :lol: ,,he,, he's gonna frickin' kill me when he reads this :lol: neener neener

 

[shoboat]

Jerry,

I am not biased on CMB engines, I have an O.S.-XM-21 that runs great on 70%. I think the O.S. lower is a nice

piece,much better than a K&B. You are right though, Tim has a lot more experience with all the outboard motors. :lol:

Having Fun Testing Already? I should be out in a week or less.

Have Fun,

Mark Sholund

 

[Jerry Wyss]

Jerry,
I am not biased on CMB engines, I have an O.S.-XM-21 that runs great on 70%. I think the O.S. lower is a nice

piece,much better than a K&B. You are right though, Tim has a lot more experience with all the outboard motors. :lol:

Having Fun Testing Already? I should be out in a week or less.

Have Fun,

Mark Sholund

OH JEEZ, Here I was worried about Jim! :lol: I gotta get a CMB here perdy soon so I can see what I'm missing,

hell, I haven't ever had a Nova either :blink: I must be sick,,,,,,,

 

[shoboat]

Jerry,

Once you try a 21 RS OB you will not need anything else. :lol:

Have you tried puting any of the O.S. piston and sleeves in the XM-21?

I was thinking about the VZ-M piston and sleeve,what do you think?

We talked about it last year,but we never got it done.

Thanks,

Mark Sholund

 

[Jerry Wyss]

I have a VZ-M P/S coming just for that reason The VZ-M is great! all the timings are right where you want them

even for an O/B,, It's also even Better in another O/B powerhead,,that'll be just my secret,,hehehe

 

[Hill Jim]

Talk to Tim Duggan about the RS, would be a great unbiased opinion. I know hes ran a few as well asmodifying some. He should be back on friday,, I know some about the Mac,, my pal "Jim" has one on a

OS lower that I made up for him. I'm completely sure they are a tough engine for being in Jim's hands

for several months now :lol: :lol: ,,he,, he's gonna frickin' kill me when he reads this :lol: neener neener

Jerry,

You never miss a chance to bust my chops :lol: :lol:

 

[Jerry Wyss]

:lol: I knew You'd catch me! :lol: You gotta admitt, a Thunder Tiger woulda been Dead Long Ago!

Hey, I bet it woke you up better than coffee, yeah?

 

[Tim_Duggan]

You are right though, Tim has a lot more experience with all the outboard motors. :lol:

Don't know where I got this reputation from????? There are far better engine builders on this forum than me. I'm no expert (sh1t - I'm racing a Thunder Tiger - what does that tell ya!) so feel free to dispute my comments. I've blown up Nova's so they aren't bulletproof either - just took 8 years to fail! I consider them to be the benchmark for 21 engines.

I have modified one RS21 OB and also looked at the remains of a very blown up RS21 OB. Like most engines there were things I liked, and things I didn't like! The one I modified had crazy crank timings and 0.008" sub piston induction. Raised the sleeve with a shim, re-adjusted the head button to suit and also reduced the bowl volume to raise the compression to where I wanted it. I also blocked off the HUGE oil supply for the front bearing. All of a sudden the engine started easily, would idle and was far easier to tune! If you want further info - contact Poolschool on here - it's his engine and I think he is happy with it now. He should be - it flies.

The one that blew up had never been opened ex factory before the big bang. There was no crank endplay because the crankpin was rubbing hard on the PTO race - hard enough to put a groove into the crankpin and to make the outer race of the bearing very dull. The hole in the PTO shaft was less than 0.003" larger than the crankpin and had sharp edges. The crank pin had no radius for the PTO pin.

I think you can guess what broke off - it wasn't the rod. Repair parts costs almost as much as much as a new engine!

The ports in the sleeve were very rough - nothing 5 minutes with a needle file wouldn't fix (- but should you have to do that on an Italian race engine?)

In summary - if you're not that proficient in checking things out properly inside an engine like what I mentioned - send it to or buy it from someone who is, before running it. Could save you some heartache and gain some good power.

I could be giving this engine a bad rap, but 2 out of 2 for major oversights that are easily rectified isn't what I'd consider a fluke. I'd consider it poor quality control.

As for the MAC's, The one I had the most exposure to was already modified by Andy so I didn't touch it. Only played with carbs, pipes and props and water cooling. Love's to rev! Very temp. specific engine. As it had already been modified I couldn't tell if there were any "oversights" that had to be rectified.

In my experience the fastest 3.5 O/B I've ever played with was a converted and modified Novarossi P5X. Loves to rev and has some serious torque too!

From what I've seen of the PLUS - they are even stronger than the P5, but have a 14.5mm crank so converting to O/B hasn't been done (yet). Seriously expensive excersize tho' - far more than a CMB or MAC + mod's from an engine guy.

Tim.

 

[Jerry Wyss]

Jerry,

Have you tried puting any of the O.S. piston and sleeves in the XM-21?

I was thinking about the VZ-M piston and sleeve,what do you think?

We talked about it last year,but we never got it done.

Thanks,

Mark Sholund

[/quote

Mark, The VZ-M P/S is not gunna work in the XM and would be way too much trouble to do so.

 

[topfuel443]

Weve tried a few different sleeves in the OS. Like Jerry said, the VZm is not worth even trying. Way too different on case porting/sleeve porting. RG sleeve seems to be the best sleeve for an XM, modified of course. Port demensions are the same, but atleast its got a good chrome sleeve. A well known Nova Rossi sleeve can also be made to fit, but it requires a bunch more work.

~James