outboard props?

[TomMoorehouse]

I dont have my outboards anymore... but got a few props that I cant help to wonder how'd they work. Has anyone tried the 2138 or 2142 on their .21 ourboard? How did they work?

 

[ggillman]

Good one Tom,

Prathers and Octuras seem to be the hot ticket.

Gene

 

[billr]

Hello guys! I posted this same thing at the RCBOAT forum also, but for best results, I came here also. I am glad to see the prop business coming up a lot. Let me tell you my results and setup before I ask the question.

I run a Hopper 260 hull with a CMB .21 Red Head on a lawless outdrive and Irwin pipe with stingers in the end. There have been a few mods to the engine and so forth, but with a standard 1440, I was running about 50 or so mph. I put on a polished Hopper modified 1440, and I was clocked at 56 mph. The pressure in the pipe became so great, my joining sleeve for the pipe and header gradually spaced more than I knew. After that point I went to a race where the course was really tight. On that course(Baton Rouge) I was clocked with radar at 50 mph. At one point in the race, I changed props to a not polished, and rough X640. This prop was not clocked, but seemed to have more speed and seemed to handle better coming out of turns better than the other,( I did not slow down as much in the turns ).

Now, after my setup stuff, here is the question: Could somebody explain the difference in a satin finish and a high glossy polish. How do you get a satin finish?

Also, has anyone had any luck increasing your speed from cutting the tongues off of the prop, or mybe even back cutting?

Thanks,

Billy Richardson

Mississippi Model Boaters Association

8)

 

[Grimracer]

Billr

What do you mean by standard 1440. Was this a (Bag) prop? Out of the bag so to speak, With only balance and light clean up.

If so this would explain the speed jump with the Hopper 1440. However i have never run a Hopper 1440 and do not know what this is. If its anything like a Anderson 1440 "it most likely is" then I got yea.

The handling became better with the X prop! This is typical and to be expected. Most 1440 are rotten at getting the boat out of the corner (remaing lift). However if the boat is kept light this becomes less. Probably dew to less hunker-down. "a grimracer-ism". The boat trying to bury its self under water as the keelson digs in.

Tom

Yes i have tried some of the props that you mentioned. It's really hard to get the boats to set on the water with them. The outer sponson lifts hard and the motor unloads big time. This is because the diameter of the props is too small. Any bigger and the prop would hit the cavatation plate. (Remember I run stock motors). I can not cut the plate. I will however be cutting a few up this summer for testing.

Grimracer

 

[Bill Richardson]

Well, the standard 1440 was an "out of the bag prop." The Hopper modified prop was the cause of the increase in speed. I guess the focus of what I was trying to get at was when I put the X640 on, it seemd not to hunker down in the turns. And the other focus was the Satin finish...how do you get it or what is the difference between a satin and a fine polish as seen in other articles.

 

[ggillman]

Hi Bill,

As far as the backcutting and mods to the blades there is a excellent page here:

http://www.rcboat.com/prop.htm

Satin is like a like a very fine grit sandblasted finish or slightly rough after sandpaper finish, highly polished is like a mirror like finish, thats the best way I know how to describe it, hope this helps, ;D

Gene

 

[Grimracer]

Billr

The reason I freaked out is because I have never been able to get a bag 1400 series prop to work on any of the tunnel boats I have tried them on. I always spin the motor so hard that the things blow up.

They also lift to much for the boats I run them on. However if I back cut them and cup them I can run the tar out of them.

Keep me up to date on the performance of the props.

Grimracer

 

[Ron Olson]

I know that most of you guys in here run 3.5 outboards but how about the 7.5's. Has anyone tried out the M447 prop? I know that some people run up to the X450 but I thought that I would give the M447 a shot. Normally I run an X447 or 448 on my tunnel.

 

[Tunnelbill]

Hey Ron,

What is the M447? Have you tried any Andy Browns

props like the 1450/3.2 and the 1450/3.6 they are very fast props on the 7.5 tunnels. TB

 

[TimD]

Does anyone out there with a PIPED 3.5 outboard have any problems with pulling a prather 215 prop or is it too big for good RPM's? Please mention what type of motor and pipe for fair results.

 

[billr]

Well I have done some experimenting on a 215 with our tunnel hulls! You really cannot beat them. I have tried it on an OS stock and reached the mid to upper 30's. There was a weekend that we all went to the lake and tried the 215's on a K&B 3.5SS which was heavily modified. It ran low 40's. It really is a good prop. It is not to little for a piped 3.5 Look at the prop database on the Intlwaters site, and compare the 215 to an X640. The 215 has a larger diameter of 1.6 and a smaller pitch of 2.5 An X640 has a smaller diameter of 1.57 and a greater of pitch of 2.512 I ran the X640 with a CMB redhead 3.5 (heavily modified with an Irwin pipe) and got roughly 50-52 mph. I would say try both.

The big experiment that we tried was to round the tips on the 215. MAN.....the difference was incredible! I told the guys that it seemed to run really well, so they tried it with the K&B SS gold head...... it FLEW!!!! probably high 30's low 40's. It even took the hopping out of one of the tunnels. Now, many club members have these as the prop or backups.

I hope this helps. If you need pictures let me know and I will post them on our club site.

Billy Richardson

 

[TimD]

Thanks Bill,

The 215 does have less pitch than the X640 and it handles better too. I'm using a different pipe to what everyone else uses and I am trying to see if it generates more torque than other pipes.

I was able to achieve over 50 MPH with the 215 prop.

 

[duc]

I use a car tuned pipe on my 8382 outboard. It runs great with the 215. Hope to post the speed I reach pretty soon. We use a Prather 220 two to. No figurs yet.

Will try the rounded tips two tnx for the tip! ;D

 

[TimD]

Seeing how we don't have a prop forum yet ;D what does rounding the tips of the prop actually do?

Bill, did this mod change the handling of the boat in any way ( did it generate more / less lift) and did you have to change the prop height or angle compared to a standard prop?

Duc, what car pipe are you using?

 

[ggillman]

Rounding the tips reduces the lift and takes the thrust cone further back, Less Lift = More Push

Gene 8)

 

[TimD]

O.K. So rounding the tips reduces lift. The next question for all us prop novices out there is " do we need to lower the prop further into the water?"

 

[billr]

Rounding the tips for me made some difference in speed. I did not lower the engine at all. another guy tried my prop and it took the hopping out of his boat, and went faster. Another guy then put it on his K&B SS gold head. Let me tell you, it smoked everbody. The owner of the boat went the next day and bought a 215 and did the same thing with a little less rounding. Works great without lowering, but experiment!

Bill Richardson

MMBA

;D

 

[ggillman]

Just rounding off the tips usually will allow you to run at the same height as before, but if the prop has heavy mods, like backcuts and tongue relief, more cup, reshaped blades, they generally need to run deeper,

depends on setup. Test it one way and then the other,

to me what you want is when the engine hits the power band on the pipe the roostertail should lay down and the speed goes up bigtime, too much roostertail and your reving out and not getting top speed, run it deeper.

Watch some of Andy Brown's rigger video's, when that tail lays down, Watch Out!!!! He is Gone!!!!!!! ;D

Gene

 

[TimD]

O.K guys,

This is the sort of stuff people like me want to know!

Can I safely assume then that a prop with little or no lift will throw a flatter roostertail than A lifting prop?

Having said that, and going by Bills comment about the rounded tips being faster - is it safe to say that too much of the motor's power is being wasted lifting the transom up out of the water? If that is the case - why is the 1440 so damned fast? ??? ???

 

[billr]

I hate 1440 out of the bag! Although I now have a 1440 modified my Mark Hopper and my Tunnel does 56 mph! 1440's have a bad tendency to slow in the turns. Most of the guys here have them, then complain about the turns. They are really fast on the straights. I talked with Jim Irwin about it, and gave me an idea. He said take an X640 and cut the tips down to the same diameter and shape as an X637. Well test results are not in after all of the cuts,but before the cuts is a different story. The 640 seemed to have the same speed or a little more in the straights and in the corners, it did not slow at all.

On the roostertail thing, well yes the rounded tips willhave less of a rooster(if you can see it good), but I find that the engine height and angle are the biggest mistakes made in field. Tom get us a PROP FORUM ;D

Bill R.