Tuning Questions

[Roxyflash]

Good speed for the low nitro.Going to 50% would give you a few more mph but may take your plug if its to lean.

 

[Blackout]

I ran 51.3 mph today. Pipe is at 10.5" and I can't make it much shorter as the 180 degree header contributes to much of the length. I found too lean as the boat went slower, so I richened it back up two clicks to get the 51.3 mph. I think I need to restrict the water cooling as the boat seems to run faster after about 3 laps. I assume this is because the engine finally gets up to temperature.

Cut the water back and richen the needle, it'll respond much better and run faster!

I'll give that a try. What head temps should I be looking for about 10 seconds after the engine is shut down? I was thinking about 175 degrees?

Thanks.

 

[glenng]

I run my surface drive Mono with a Cmb at 9-1/2" (from the glow plug to the widest part) and thats with a 455/3 blade.

It gets on the pipe at 3/4 throttle. Looking at your pics it looks way long,also get you a 45 needle the 67 will be hard to fine tune.

Your pipe is measured around the exhaust curve which makes the pipe alot longer than,lets say a exhaust that comes out the back of a motor IE: Mac,CMB,Picco 45's.

Tim

I finally got my Speedmaster .45 in the water. I am still breaking in the motor, but have a few questions. The engine is an O.S. 46VX-M with a Macs 7.5 marine pipe at 11 7/8" long. I have no idea what speeds I am running, but when I go from 3/4 to full throttle there is no change in engine speed. Is this a sign of a rich engine or too long a pipe? Or a combination of both? My high speed needle is only at 1 turn out, but I had to convert to a remote needle so I am using a 9B remote needle. This needle is really designed for a .67 and up engine. Prop is a stock X450/3. Thanks for any help.

Here are some pictures of the boat.

Don Ferrette suggested I use the O.S. 40A needle in my 45 boat-same threads as 9B-screws right into one of Don's Jackrabbit bases.

 

[TimothyJones]

I would take his advice.I do all the time and it has worked for me.

Tim

I run my surface drive Mono with a Cmb at 9-1/2" (from the glow plug to the widest part) and thats with a 455/3 blade.

It gets on the pipe at 3/4 throttle. Looking at your pics it looks way long,also get you a 45 needle the 67 will be hard to fine tune.

Your pipe is measured around the exhaust curve which makes the pipe alot longer than,lets say a exhaust that comes out the back of a motor IE: Mac,CMB,Picco 45's.

Tim

I finally got my Speedmaster .45 in the water. I am still breaking in the motor, but have a few questions. The engine is an O.S. 46VX-M with a Macs 7.5 marine pipe at 11 7/8" long. I have no idea what speeds I am running, but when I go from 3/4 to full throttle there is no change in engine speed. Is this a sign of a rich engine or too long a pipe? Or a combination of both? My high speed needle is only at 1 turn out, but I had to convert to a remote needle so I am using a 9B remote needle. This needle is really designed for a .67 and up engine. Prop is a stock X450/3. Thanks for any help.

Here are some pictures of the boat.

Don Ferrette suggested I use the O.S. 40A needle in my 45 boat-same threads as 9B-screws right into one of Don's Jackrabbit bases.