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Unknown Boat +tuning questions

Old 07-06-2005, 09:29 AM
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Default RE: Unknown Boat +tuning questions

Ron, that's ok. I screwed up too.. It was the 04 Fun Run that I put fuel in my eyes.. [&o] How time flies when having fun!!
Old 07-06-2005, 12:34 PM
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Default RE: Unknown Boat +tuning questions

That wasn't fun, it scared the heck out of me! I thought for sure that we were going to have to run you to the Hospital. Fortunately we have one close by, just on the other side of the fence of the park. You got real lucky as someone did have fresh water with them to rinse your eyes out with.
Old 07-06-2005, 02:38 PM
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Default RE: Unknown Boat +tuning questions

Those were my thoughts at the moment.. Glad there was clean water near by..
Old 07-06-2005, 03:09 PM
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Default RE: Unknown Boat +tuning questions

Ya know I was using long plugs- That is what came in it when I got it and just kept getting the same size. I DID however just get back from the shop and picked up a couple OS #8 plugs. They are shorter than the ones I have been trying and no pesky idle bar


Im upset no one commented on my little video! Crushed even! Ha, I know its not exciting but there will be more to come for sure. Nice host for them as well.

Fuel tank is a 14oz that I fill to about 2/3 I guess. I was incorrect when I said it was a 17oz earlier but I was mistaken I went with the smaller one after all. It is still a little bit larger than the original one which was a Du Bro also and on the size it says S-6. It is a bit smaller- I wonder if it was a 6oz. I would not think the slightly larger tank would not be an issue b/c I do not by any means "top it off" so the added weight is very small. I keep it right below the seal just to insure no fule comes out. The pickup and breather lines should be fine in the tank, the fuel pickup hits the back of the tank so it would have to be pretty empty to starve for fuel. I am also going to put a one way valve on the line going from the muffler to the tank to keep it pressurized. Was something I read somewhere.


OK also I got a lil crazy and added some flames to the front of the hull- I am not sure if I like them. What do you all think? I am for sure going to put some more clear coats on it- might have it done. The candy apple paint job already looks great and looks 10x when wet. I need that look allll the time. [8D]









And here is the watercooling/ fuel setup. I changed the tubes so it hits the head then the water jacket as suggested above.






Again I know the inside needs to be repainted One thing at a time. The fuel seems to disolve the yellow that the original owner had used.








Old 07-06-2005, 06:30 PM
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Default RE: Unknown Boat +tuning questions

Sorry about that.. Got carried away at work, downloading vid now. Dialup sucks!

If you are concerned that the fuel might leak, I'd check to make sure it doesn't. If there are no leaks, fill the tank full.. If it does leak, that could be the problem. Also, make sure the pickup / breather tubes are not directly against the tank. If that occurs, it could cause starving problems. Been there, done that. I've gotten into the habit of cutting a slot on the pick up line so that won't occur again. Are these lines brass tube or using the supplied clunker?

Ths S-6 is a 6oz tank. Weight is not the concern I had with the tank size. If it works, use it. I've used a one way valve, but only on my exhaust throttled motors since this needs crank pressure vs pipe.


Still waiting for the vid to be downloaded.. [&o]

Oh yea, flames look cool!!! The interior of the boat needs to be clear coated also. Or the paint will keep flake'n away. What do you use for clear coat? Myself, PPG 2021 with reducer / hardner mixed..
Old 07-06-2005, 07:00 PM
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Default RE: Unknown Boat +tuning questions

Sure do get the alligators view of the boat running! Looks good on plane.. Will be better once you can open up the throttle...
Old 07-06-2005, 07:28 PM
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Default RE: Unknown Boat +tuning questions

OK I guess I made some progress.. It now goes about 10 ft and then dies [>:]

One question I have is approx where should the idle needle be set to? Ihave tried suggestons made here but with no luck. I also checked the mfg's web site and there Q&A area. Found here -> http://www.mecoa.com/faq/carb/needle_marine.htm

It suggests turning the main needle to 3 to 5 turns. At 3 turns it spits fuel out the back and smokes just a tad. Later in the faq it says smoke is bad (duh) so I am skared to turn the needle more- wouldnt that be worse? But at 3 turns it doesnt seem to be enough. I have tried it at 2-2.5 and 3 turns and then tried the idle screw all the way out (closed) through all the way in (wide open). It still dies after about 10 ft. It is trying. It had been dying as soon as it hits the water- now it goes 10-15 ft and tried to keep going before it dies.

Generaly speaking- should the carb look more like A or B in this crude pic of mine? Or maybe somewhere in the middle? Or more? I have tried it all the way from closed to open and still no luck.







Thanks again for you guy's help. Im close to thinking this engine is funky and go get a new one. However I have faith in it. It ran for 20 min a few nights ago so I think it can run again. I just need to figure this out.

Old 07-06-2005, 10:52 PM
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Default RE: Unknown Boat +tuning questions

Sorry about not commenting on the video. I'm on the tin can and a string dial-up also so when it finally played I missed most of it. I'll have to try it again.
OK, what's next. The tank is the SS-6 which is a Slant-top Square 6 oz. tank. You can go up to a 8 oz. later if you want to for a little more run time.
You can take the needle out a little farther to around 3-1/2 turns. Adjust it to where you get a slight lag when you blip the throttle. The idle screw on carbs in boats basically holds the barrel in place as you only want it in far enough to where you can close the barrel fully to shut it down.
Your drawing is showing the carb barrel right about where it should be, between A and B.
I like the flames, you did a god job on them, I love hot licks on anything.
I'm thinking that your hull is a Prather. A Dumas from that era is kind of close but not with the windshield and the separate radio box.
Keep on messing with the boat, it'll give you a lot of experience for down the road when you decide to upgrade. I'd start one from sctratch if you decide to go with another powerplant that way you can go to a flex cable surface drive without messing that hull up.
I probably missed something, I always seem to.
Old 07-07-2005, 06:04 AM
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Default RE: Unknown Boat +tuning questions

Pic A is where you want to start the motor. WIDE OPEN is where you want to run. You do have an older style K&B motor.. Just wondering if the bearings, piston/sleeve, carb, gasket or ??? is bad... Something is wrong and just won't let that motor sing. How does the motor run when not in water? Needle setting should be around 3 - 3 1/2 turns out.. If possible, pick up some McCoy MC9 or K&B L1 (both plugs will need two washers on the plug) plugs. That OS 8 might not work for the motor. Plugs are made for different applications - heat ranges etc. K&B does make a S1 (S = short), but believe it has the idle bar.

Have you taken the motor apart lately? (I need to go back and reread from the begining) Could be the sleeve is not mounted in the correct spot. Another carb to try? Keep working on it..
Old 07-07-2005, 03:38 PM
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Default RE: Unknown Boat +tuning questions

When the boat is out of the water and I use my lil hand pump to push water through the cooling system it will run great/ idle down if i want it to. Its just under load it doesnt seem to like.

I am pretty sure it still has good compression, I can hear it pressurizing as I turn the driveshaft. The 3 local hobby shops dont have any idea what to do. The original owner doesnt remember any of it (I asked him today about it). I know this all seems soo simple but I just cant get it to run in the water again. I am going to mess with it again this evening until I get mad and come back home lol.

I am starting to just want a new motor for the boat. I have heard of flex drives in here and I am assuming they are better but cant I just put a new engine in there and have it mate up to my driveshaft? The prop driver just screws onto the prop stud. I would assume it would be a matter of matching up the threads.

I am going to keep messing with this thing but I am going to start looking at engine options. If I am going to keep it for a while (which I plan on doing) wouldnt a nice new engine be a good idea? I mean I have prob spent 40 hrs at home and prob 10+ at the lake trying to get it to run. I about cant afford to keep trying to get it to run. the $$ a new engine would cost is worth it to me.



Old 07-07-2005, 04:20 PM
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Default RE: Unknown Boat +tuning questions

Don't know if this area was touched at all.. Take the flex shaft out and inspect it.. Are there any broken strands? Man, this has got me stumped.. [:@]

Raise the prop a tad bit. Maybe there's just too much load on the motor. But you did state it ran 20 mins once..
Old 07-07-2005, 04:29 PM
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Default RE: Unknown Boat +tuning questions

How long is the pipe length? Measure from the plug to the weld on the pipe where the two cones meet.. It appears that the pipe coupler could be too long. Did you change this when the boat transfered over to you? Believe that motor orginally came with the can muffler that is now used on the SS motors.
Old 07-07-2005, 04:36 PM
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Default RE: Unknown Boat +tuning questions

The pipe is the one that came on it. It was 12in. total lenght. I took 3/4 an inch off the total length. From the cylinder/plug to the weld it is 7 3/4in. and the total length is 11 1/4in.

And its a direct drive I guess they call it- no flexshaft. And when the motor is not in the boat the shaft will spin like its on ball bearings (even though it is not).

Also the guy at the local shop suggested that after the motor heats up the sleve could be getting slack on it and loose compression. I didnt think that was an issue b/c it did run once and when I turn the motor over you can hear a suction cup sound on one portion of the stroke- so I think its still got good compression.
Old 07-07-2005, 06:00 PM
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Default RE: Unknown Boat +tuning questions

The pipe sounds too short. When the pipe is too short, you will have problems getting the needle set right. It will either be too rich or too lean, and impossible to get the right setting. I'm running a rear exhaust K&B 3.5 in a plane. This is a very similar engine, but with a front case designed for airplane props rather than a flywheel. With the prop I'm using right now, the engine turns around 17K RPMs, faster than yours sounded in the video. The pipe measures 263mm (10.4 inches) from the plug to the weld. When I tried moving my pipe a bit shorter, I couldn't get the needle adjustment right. Check your measurement, and perhaps pull it out some for now.

If you haven't done so already, go back to the smaller tank. Larger is not necessarily better when it comes to tanks. Using one that's too big allows the fuel to slosh around and also results in a major difference between mixture as the tank empties. You should also do a pressure test to confirm that the tank doesn't leak. Put a piece of fuel line on one tank pipe. Put a finger over the other tank pipe and blow into the line. No pressure should leak from the tank. If it does, you need to find out where the leak is.

About plugs. My K&B 3.5s have always been happiest when running K&B 1S non-idle bar (part #7321) plugs. Since I still have an adequate supply of them I haven't tried something like an OS #8 (which I use for many of my airplane engines). You can order these from Mecoa if your local hobby shop doesn't have them.

If your engine is too lean, it will die not long after you launch it. You may want to go back to the recommended 3 1/2 turns out and see what happens. Note, this will lead to an idle that I would call sloppy rich. Throttle response will be a bit sluggish, as Ron described. However, if you tune it on the shore for a good idle and crisp throttle response, it's almost certainly too lean.

That's all for now. The video proves the engine will run. Changing to another engine will not get you past the problem of learning to tune it right. Better to learn this on the one you've got than spend $ on something new and have the same problems, or worse, ruin a new engine.
Old 07-07-2005, 06:43 PM
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Default RE: Unknown Boat +tuning questions

Very nice info there. I was able to slide the piece of muffler pipe I cut off back into the hose that connects the muffler to the water jacket. The flexible water hose is a few inches long, so the little piece that was cut is now inside it acting as a spacer. The muffler is now snug up against that. So now my pipe is back to stock length. I thought about leaving it out and pulling the muffler back out a lil, but I did not think that was smart due to a 3/4 in gap in the metal portion of the exhaust (inide the rubber hose). That wont transfer heat off the motor so that is a no go. I will need to get a new tuned pipe, but this should do for now.

I will have to purchase a smaller fuel tank, I dont trust the one that came in it ( very dirty etc etc).


Here are a few pics of the motor I just took. You can see the black hose I mentioned above. I would go try it but its a little late in the day. I will have to go in the morning for sure













One other question, as to the steering/rudder. Mine is now all metal- Servo gears (Hitech HS5645MG) servo arm, linkage etc. Well when the boat was running it will turn right very sharp but barleyyyyy turns left. I figure that is due to 2 things. One the rudder is ofset to the right of the prop about a 1/2 inch or so. Another factor being the torque that the prop produces makes the boat lean to the right a bit and thus sinks the rudder deeper I guess? I have seen some dual rudder setups before but not sure where to look. I am sure an easy fix would be to move it to the center of the boat. But will it be less effective in the prop wash? Seems like it would be.

And a pic of the rudder and cav plates.







Thanks again for all the help.





Old 07-07-2005, 07:46 PM
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Default RE: Unknown Boat +tuning questions

Don't worry about a new pipe right now, the long hose with the spacer is fine.

As long as the rubber stopper on the original tank is still flexible, and it's not leaking, it should be ok. To clean it, remove the stopper and pour in a little rubbing alcohol. This will cut the old oil and stuff that's in the tank. Once it's clean, confirm that the stopper is ok and if so, reassemble it.

Boat racing is done clockwise around a big oval. That means the boats are setup to go straight and make right turns. Left is usually only used for occasional course corrections or perhaps collision avoidance. You could change the rudder setup, but my suggestion is to make the most of what you have. Use it as a platform to learn with. When you start itching for something bigger or faster, start looking at building a new boat.

And one more question. Is that a remote needle valve I see in the latest pictures? If so, any of our suggestions about initial needle settings are meaningless. I'm not saying it's a bad thing, but I think all of us were assuming (and we all know why we shouldn't do this) that you had the stock needle. Since it's not the original needle, you're on your own for finding the right setting.
Old 07-07-2005, 07:59 PM
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Default RE: Unknown Boat +tuning questions

/me nods


Yes it is a remote needle. I thought that is how all of these motors/ carbs were. Thought you all were aware of that from the getgo- sorry. Maybe that would explain why it was running that one evening on 2 1/4 to 2 3/4 tuns before the battery for the reciever got low. Also picked up a nice 5 cell 1100mAh for the reciever to use when the 270mAh pack that the radio came with runs out.

I am trying to remember if I had cut the pipe before that evening. I think I cut it after I got home. I want to say I was going to cut it before I had gone out that day but I did not want to make a change like that when the boat still had not run in the water yet.

I have to get back to work tomorrow But I will be messing with it this weekend.

Old 07-11-2005, 09:59 AM
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Default RE: Unknown Boat +tuning questions

More suggestions/comments.

1: Make sure the fuel lines are short as possible, but not to short as they might get pinched. Put a 6 or 8 oz tank in there.
2: I did notice the remote needle from the start, still start around 4 turns out and lean in from there. When motor is running, place your hand behind the pipe. Should have oil coming out. To much oil will be rich, none there it's lean. 3: On an run attempt, bypass the exhaust cool'n, might be making the motor to cold.
4: There should be a gap between the header and pipe. If they touch, you could end up with radio problems.
5: As stated, you pipe may be to short. Make 1/8" adjustments at a time.

Sorry, didn't get parts shipped out Friday, will get them out Wednesday.
Old 07-11-2005, 03:51 PM
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Default RE: Unknown Boat +tuning questions

Thanks, I will try what you suggested. I know it does not spit fuel/ oil out the back- One time I was messing with it and it started to spray it on my tools lol so I turned it back down thinking this was the max it could go. I know when a regular engine spits fuel out that isnt good. I guess that is the norm for these engines?

Either way that could be the answer right there. Just hasnt had enough turns on the needle.

I hope so. I messed with it for a longggggg time this weekend with no luck. Would go about 15ft and it was tryin to go but would bog down and die.

Old 07-12-2005, 08:19 AM
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Default RE: Unknown Boat +tuning questions

Spitting out a bit of fuel when starting is fine. Once the throttle is opened it'll be sucked in. If the motor will sing when starting the boat and bogs/dies on water, the prop may be too deep. Either bring the prop up 1/16" or try a smaller prop..

I had a motor run so so once, knew there was something wrong. After a total tear down, it was the bearings. If you get a chance tear down the motor and roll the bearings while holding the inner race with fingers. Inspect the bearings, piston, sleeve, rod, etc for scratches..

The carb could be the issue if it had sat for a length of time with fuel in it. Fuel will gum up the inner parts and cause hair to be pulled out. It'll look fine, trust me.. If you have another carb, try that...

Keep looking, don't give up....

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