New member

[Greg Ruggles]

Hello everyone, just joined and am excited to start learning. My name is Greg and I have a 40" Dumas Scarb 337. It has a .46 O S Max VRM in it. I bought this boat when I was 16 and now I'm 61. I destroyed the stuffing tube back in 1980 and it sat in the rafters ever since. This past February 2024, I fix it up and got her wet. Quick question, is there a tuned pipe on the market for this engine? I want to go faster... who doesn't right?
Here's what the boat looks like now.

 

[Danny King]

Welcome aboard. Have a pic of the inside?

 

[Greg Ruggles]

This is what I've got. I'm told that this is NOT a tuned pipe for this engine. I've looked at a lot of websites and can not find anything for this engine. The engine runs great, tops out probably between upper 30's to low to mid 40's. I just bought a Picco 90 with a tuned pipe and a 5" engine mount for $300.00. I was thinking of putting it in the 40"Scarab,but people are telling me that would be to much engine for that size. I may now but a 47" Catamaran from Bonzi Sports and put the Picco in that instead. I may look at getting a CMB .67 and install that in the 40". I need more speed. I've also heard that putting a OPS 60~67 tuned pipe on the .46 engine would increase performance...but I was told by other people that it would hurt the performance be cause of "Lack of back Pressure". Like I stated earlier, I'm looking to learn and gather information. Here are some pics of the inside guts of the boat.

 

[Danny King]

This is what I've got. I'm told that this is NOT a tuned pipe for this engine. I've looked at a lot of websites and can not find anything for this engine. The engine runs great, tops out probably between upper 30's to low to mid 40's. I just bought a Picco 90 with a tuned pipe and a 5" engine mount for $300.00. I was thinking of putting it in the 40"Scarab,but people are telling me that would be to much engine for that size. I may now but a 47" Catamaran from Bonzi Sports and put the Picco in that instead. I may look at getting a CMB .67 and install that in the 40". I need more speed. I've also heard that putting a OPS 60~67 tuned pipe on the .46 engine would increase performance...but I was told by other people that it would hurt the performance be cause of "Lack of back Pressure". Like I stated earlier, I'm looking to learn and gather information. Here are some pics of the inside guts of the boat.

Lmao. Welcome to rc boating. Lots of opinions and many ways to go about it.
There is no substitute for lake time. Overthinking can be a killer.
Be patient and REMEMBER EVERYTHING!
Just because something didn’t work once doesn’t mean it doesn’t work.
What is the pipe length. From the plug to the pressure fitting

 

[K F Wheeler]

Welcome to R/C boating!
Sounds like you got bit by the bug... Well, got plenty of people on this site to help you with your questions. And, can sympathize with your affliction!

Ken

 

[Greg Ruggles]

Lmao. Welcome to rc boating. Lots of opinions and many ways to go about it.
There is no substitute for lake time. Overthinking can be a killer.
Be patient and REMEMBER EVERYTHING!
Just because something didn’t work once doesn’t mean it doesn’t work.
What is the pipe length. From the plug to the pressure fitting

Sorry for the long response time. I measured from center of glow plug to the pressure fitting and got 8.25".

 

[Danny King]

Sorry for the long response time. I measured from center of glow plug to the pressure fitting and got 8.25".

That is short. Should be around 10-10.25” to start. And will need more prop.

 

[Greg Ruggles]

That is short. Should be around 10-10.25” to start. And will need more prop.

I currently am running an X450, 2 blade. A X452 ran slower. How can I lengthen the pipe?

 

[BradFoster]

Welcome, IW is a great site for our Hobby

 

[Greg Ruggles]

Welcome, IW is a great site for our Hobby

Thanks Brad, I see there's a lot of people from Michigan. I'm about 30 minutes north of Detroit.

 

[Jeff Barnes]

Welcome Greg I run a mono boat about that size I run a 450/3 blade and pipe length about 9 3/4 from plug to center weld on pipe I'm in the Saginaw Bay club about an hour or so north of you we have a lot of club races stop by in the spring Jeff Barnes

 

[Greg Ruggles]

Welcome Greg I run a mono boat about that size I run a 450/3 blade and pipe length about 9 3/4 from plug to center weld on pipe I'm in the Saginaw Bay club about an hour or so north of you we have a lot of club races stop by in the spring Jeff Barnes

How can I lengthen the pipe???

 

[Greg Ruggles]

How can I lengthen the pipe???

I've ran a 450, 3 blade when there's a little chop on the water. 2 blade when the wather is smooth.

 

[Jeff Barnes]

Greg now that I look at your picture better that pipe looks way to big for that motor here's what I run it's a ops 6280 pipe I measure from center of plug to weld 9 3/4 I have a pipe that might work better for you I can send it to you to try

 

[Greg Ruggles]

Well I definitely would appreciate that, it will have to wait until next year, I put the boat to bed for the season. I'll give you a holler next year. In the mean time, I'll check chkeep gathering information.

 

[tnrcboatracer]

When measuring the pipe length, I measure straight along the pipe centerline from the center of the cylinder to the weld or mid point of the band. You can sleeve the exhaust outlet to raise back pressure when using a larger pipe. Tuning the diameter of the outlet is also a thing.

 

[Alan Elzer]

Sorry for the long response time. I measured from center of glow plug to the pressure fitting and got 8.25".

Welcome Greg
We normally measure to the center of the midsection of the pipe. Where your measuring isn't the midsection. Where the pressure fitting is the beginning, look closer at the pipe, about 1.750 to 2 inches back look for a ridge or seem where a cone on inside may have been molded inside. This it the tail cone of the pipe mark it. Then measure between the marks ,that's the center of the pipe to measure pipe length in future. I would say about an 1.250" back from pressure fitting is close. But you should be about 10.5 ".
A better prop choice would be ABC 1914-15-60/3 OR 1915-23-50/3. I can help you with these ready to run props as well, as I'm a dealer & sell raw or finished props from ABC.
You can reach me on here, [email protected] or call leave a message 812-453-8137. Alan