mac temp.

[k&b guy]

what temp. are you guys running to get the mac to "wake up"? tnx.

CARTER

 

[julianconde]

Mac what 21,45,67,84 ??

 

[k&b guy]

.21 o.b. sorry.

CARTER

 

[julianconde]

ok i run Mac Outboards i normally what i do is restraint the water comming out the engine. upon startup i let the engine heat up considerably until when you can touch the head then i tell my pitman to throw the boat it.

what lower prop and pipe are you using on your boat and also whats the Hull ?

julian

 

[k&b guy]

ts2- k&b lower- x438- silver bullet hp.

 

[julianconde]

ok k Sharpen and balance X438 or a Mark Sholund X438. you are on the right track get the Silver Bullet Pipe at 8 inches from the center of the plug to the center of the PIPE and 65% Nitro. I dont know a setup on the TS2 boat you might want to ask someone else on that but the engine is good to go in my books thats my setup that i us as far as power and fuel ,pipe and prop my friend let me know if you have more questions ok..

julian

 

[Rokieboater]

I took the water cooling head off and switched it to a MAC air cooled head with three fins cut off. Motor runs best when it runs hot. Tried the water cooled head with it constricted and ran best with the air cooled head.

Motor also ran best with an Irwin pipe or a cooper pipe.

Just my .02 cents

Robert

 

[k&b guy]

thanks robert. i`m where you were at. eliminated water completely. wrapped fins behind water jacket.can not reach 190. where did you get your aircooled head at? appreciate your help.

CARTER

 

[shoboat]

Carter,

You need to reduce the cup on the X-438 for the MAC OB - 21 motor.

They like to spin up for best results.

Have Fun Testing,

Mark Sholund

 

[Rokieboater]

thanks robert. i`m where you were at. eliminated water completely. wrapped fins behind water jacket.can not reach 190. where did you get your aircooled head at? appreciate your help.

CARTER

Yes I agree with Mark on a reduced cup prop. I also ran a X-637 that spun up nice. I got my aircooled head from www.cmdracing.com Same company that makes your motor. He makes a buggy motor that has the air cooled head. You can call or e-mail them.

Good Luck

Robert Holland

 

[Andy Brown]

We still have plenty of the aircooled heads in stock. $35 shipped. We also got the best results with aircooled head. Run .006 -.007 head clearence.....however, I do know that Julian is getting good results with more clearence.

 

[k&b guy]

thanks for the info andy.

CARTER

 

[julianconde]

thats correct Mr Andy Brown but i will not disclose the head clearance im running now.. Heat is not the problem guys is the fact you have to run the right pipe and head clearance a SSP NR21 carbon fiber pipe will work extremely good on then mac 21 along with the props stated above..

julian

 

[John Knight]

We still have plenty of the aircooled heads in stock. $35 shipped. We also got the best results with aircooled head. Run .006 -.007 head clearence.....however, I do know that Julian is getting good results with more clearence.

Has anyone tried the air cooled heads with the MAC21 inboards? If so, what have been the results?

 

[k&b guy]

i remember reading a while back where someone was going to make a insulator out of g-10, 1/32" for between the powerhead/lower unit. never heard how it turned out. i made a gasket 1/32" out of regular gasket material. oil,water,gas,solvent resistant. haven`t tried it yet. am i wasting my time with gasket material?. input appreciated.

CARTER

 

[julianconde]

why would you want to do that ?? just currious i dont use any does not give you any performance gains..

julian

 

[moparbarn]

We still have plenty of the aircooled heads in stock. $35 shipped. We also got the best results with aircooled head. Run .006 -.007 head clearence.....however, I do know that Julian is getting good results with more clearence.

Has anyone tried the air cooled heads with the MAC21 inboards? If so, what have been the results?

john, i picked an AB modded mac buggy engine to put in my wife's nitro buggy, i'm also gonna try it in my jae. want to see how it compares to my cmb .21 LS evo2's. maybe by the wtc, i'll keep ya posted .

 

[julianconde]

Robin it wil work I have seen it done a ssp carbon fiber hydro pipe will work very good and that buggy engine. I got a conversion for a outboard to make it to a inboard with the aircooled head.

Julian

 

[k&b guy]

julian, you`re on this forum alot. are you telling me you never read anybody talking about the aluminum lower drawing the heat out of the engine? my lake temp. is 42 now. air is 55. i guess your boats are an exception to the rule. there`s power in heat. you never said what temp. your macs run at. or is this also info you don`t want to give out? i`m done.

CARTER

 

[Andy Brown]

The MAC OB likes heat. We ran the stock Buggy engine in a mono, but with the OB water jacket and black carb.

Inside the mono the engine builds plenty of heat. Ran the AB 21 parabolic pipe and an X440/3. Was good for 54 mph on 60%