NEED SETUP HELP 21 CAT

[tom galdys]

I Have a 21 Aeromarine cat. Running a 5 port NR, Think it has a NR pipe and am running exhaust thru the transum using larger tube and coupler hose(3/4" ID). What should my pipe length be and what prop. Also,the strut is under the boat and what height should it be. Can replace pipe with OPS3280 and run it up thru the cowl. Don't really want to cut it up but I will. Have tried a x440/3,x440/2, x640, x442/2. Need help from the pros for the proper setup. PLEASE HELP. Thanks Tom

 

[BeaverGuy]

Tom - I'm no "pro", but I have some experience setting up my Aeromarine cat powered by an OS 21RG which is probably not as highly tuned as your NR. I'm using an X442/2 with good results. Reducing the plug-to-pipe distance to get this thing on the pipe has been a problem since I'm not willing to cut the cowl. I runs well, but is not on the pipe with the AB 21 Parabolic pipe inside the right side of the boat exiting through the transom. The centerline of the strut bore is set at the same level as the bottom of the rear tunnels. Pix available. - Chris

 

[Glenn Quarles]

I Have a 21 Aeromarine cat. Running a 5 port NR, Think it has a NR pipe and am running exhaust thru the transum using larger tube and coupler hose(3/4" ID). What should my pipe length be and what prop. Also,the strut is under the boat and what height should it be. Can replace pipe with OPS3280 and run it up thru the cowl. Don't really want to cut it up but I will. Have tried a x440/3,x440/2, x640, x442/2. Need help from the pros for the proper setup. PLEASE HELP. Thanks Tom

Tom, I have set up several Aeromarine .21 cat boats and they can be a blast! I always adjust the strut so it sits flat on the table with the boat. I set it up like that and never move it. The Nova pipe will work great, but you will want to shorten it up to about 3.5" measured from the side of the head back to the high point on the pipe. The X440/3 is a good prop...my son's first boat like this would run 50 mph solid every time. If I can get the time I will post pictures of how I cut the cowl on my wife's cat boat. It takes away from the turbin look, but works well and I still think it looks kinda neat.

Glenn

 

[Ron Olson]

Geez, it's been a long time since I worked on an almost similar Cat, Aeromarine with the blue head NR. I had a sneezed purple head so I swapped out the jacket and combustion chamber. A local guy had it and it was a dog so he had me go through the whole thing for him. I finished it just as he was getting ready to move to Missouri so I never saw it run once it was done.

I set it up using the other pipe measuring system at 8-1/2" and I think an Octura X-440. As far as I know, the boat is somewhere in Florida now as the guys brother got it.

 

[tom galdys]

Glenn, When you mentioned the pipe measurement, What is the side of the head back? The back of the motor or from the plug? Thanks Tom

 

[Ron Olson]

Glenn's measurement goes from the glow plug straight back to where the divergent and convergent cones of the pipe meet (the fancy way of saying the widest part of the pipe).

 

[tom galdys]

Thanks Ron, That's the way I would measure it but he said the side of the head back. i would just like a clarification. Thanks Tom

 

[Glenn Quarles]

Thanks Ron, That's the way I would measure it but he said the side of the head back. i would just like a clarification. Thanks Tom

Tom, Ron is close, but I do measure it from the side of the head (even with the glow plug...basically at the point where the header/pipe come closest to the side of the head) back to the high point of the pipe.

Glenn