mac 21 ob / cooper pipe

[bob miller]

any one using a cooper pipe with a mac 21 ob ? what length works best ? did you shorten the pipe ?...thanks...bob

 

[julianconde]

I never Shortened the pipe but I did on the header I will give you all the measurements from my setup when I get off work ok at noon. Ok take care

julian

 

[bob miller]

I never Shortened the pipe but I did on the header I will give you all the measurements from my setup when I get off work ok at noon. Ok take care

julian

thanks for the reply , let me know how you measure the total length of pipe and header...bob

 

[bob miller]

I never Shortened the pipe but I did on the header I will give you all the measurements from my setup when I get off work ok at noon. Ok take care

julian

thanks for the reply , let me know how you measure the total length of pipe and header...bob

what is your favorite pipe for the mac 21 ob, the silver bullit or tha cooper ?...bob

 

[David Kingston]

I like the silver bullet

Tried SSP OB pipe but cause i live in a hot area, i found that it was hard to keep it on pipe due to the humidity. Not that there is anything wrong with the SPP pipe. I found that with the Silver Bullet pipe im now able to run hard all day without mucking about with anything and its running more consistant.

Dave

 

[julianconde]

The best pipe Is the silver bullet original pipe works perfect and the boat gets on the pipe really fast.

I take a piece of sting start from the middle of the glowplug and measure to the widest pairt of the pipe then I take that and get the lenth. Pretty simple. I'm gonna do some testing with the Silver bullet HP pipe so we will see lol.

 

[gadjit69]

hi,i just put a new mac ob on my lynx.i believe htb put out a couple pipes out,how can u tell witch pipe is original?...thanks again..lil al

 

[John Knight]

hi,i just put a new mac ob on my lynx.i believe htb put out a couple pipes out,how can u tell witch pipe is original?...thanks again..lil al

Take a look at Mark Hoppers website at http://www.htbboats.com Look for the pipes link and the photos are there. The standard pipe has a longer center section, the HP pipe has a shorter center section.

 

[gadjit69]

hi,thanks for the info...have too look at mine in the am

 

[julianconde]

The original silver bullet pipe like John said is longer and thinner the HP pipe is shorter than the original and thicker than the original also.

 

[LarryConrad]

Silver Bullet HP and Irwin muffled are what I have run on my Macs. I picked up a couple of Cooper's to test, but my recent career change,and move put my toy boat testing and racing on hold for the season. The standard Silver Bullet is another one I need to test...but I sent the one I had to Iowa. My headers are only long enough to secure the pipe coupler. Irwin pipe has the inlet trimmed even with the weld...180* U. Silver Bullet HP is just the way it comes from Mark...no trimming. I ran the Irwin butted tight to the header, The Silver Bullet HP out a 1/4" from the header. Performance is very close between the two, but I raced last season with the Bullet.

Larry

 

[julianconde]

Same here just tested the silver bullet hp pipe and it performed beutiful and with plenty of power. You can go wrong with either pipe. It worked for me I just had to chase the needle bit once I got it dialed in it loved it.

So my recomendation you can go with either pipe just as it comes from mark hopper no trimming done to it.

 

[Tim_Duggan]

Interesting - I couldn't get the pipe short enough with the Silver Bullet pipe for the mac to be happy. It was way more impressive for me with a pipe that had the distance from plug to the stinger shorter (in other words, a pipe with a steeper set of cones and less belly). Maybe it was just my combination - HTB290 and OS leg? Oh and yes - I did try the modified carb. Tried several carbs on it.

 

[bob miller]

i am still trying to get my mac to get back on pipe after a slow down...i have tried the cooper pipe and the silver bullit pipe...i have used the 437 three prop and the 438 prop s+b...my boat is the 21 vision...60% nitro...tried various carb settings and different pipe lengths...any suggestions or helpfull tips will appreciated...thanks...bob

 

[RaceCraftBearings]

i am still trying to get my mac to get back on pipe after a slow down...i have tried the cooper pipe and the silver bullit pipe...i have used the 437 three prop and the 438 prop s+b...my boat is the 21 vision...60% nitro...tried various carb settings and different pipe lengths...any suggestions or helpfull tips will appreciated...thanks...bob

Check your PTO and Main Bearings they could be holding you back!

No I dont sell bearings anymore so thats not why I am saying this LOL.

 

[Jerry Wyss]

My findings are that the Mac O/B is a Kantankerous Kod of the highest level. You have my sympathies Bob,, Good luck!

 

[bob miller]

i am still trying to get my mac to get back on pipe after a slow down...i have tried the cooper pipe and the silver bullit pipe...i have used the 437 three prop and the 438 prop s+b...my boat is the 21 vision...60% nitro...tried various carb settings and different pipe lengths...any suggestions or helpfull tips will appreciated...thanks...bob

Check your PTO and Main Bearings they could be holding you back!

No I dont sell bearings anymore so thats not why I am saying this LOL.

i just recently had rod gerhty replace bearings and modify my props...bob

 

[bob miller]

My findings are that the Mac O/B is a Kantankerous Kod of the highest level. You have my sympathies Bob,, Good luck!

i hate to give up on the motor because when she gets on the pipe she is ballistic...bob

 

[Jerry Wyss]

My findings are that the Mac O/B is a Kantankerous Kod of the highest level. You have my sympathies Bob,, Good luck!

i hate to give up on the motor because when she gets on the pipe she is ballistic...bob

Your absolutely correct there, they can come un-corked like no other. The problem is getting it to do that consistantly.

 

[julianconde]

well i have had alot of success with my HTB 290 set up with a Mac on a Lawless and actually i just finished setting one up this past weekend and its very fast and reliable had to find the needle but after that no problems. As far as reliability is concered my engines run perfect everytime they get on pipe right away and have no issues..

Tim you have to shortened you header just a little bit and leave the Silver Bullet pipe alone just like it comes from mark hopper ill give you in a minute my pipe lenth. I run a sharpened and Balanced X438 thats it on 65% ron drake fuel.

Same thing with my other HTB 290 i just put together with a Silver Bullet HP pipe i have no complaints ever im a very happy camper thats why i have 13 of them in my spare engine box lol..