.21 OS R/C boat engine!!!

[Glasply150]

Hey guys gotta kick question for you. I recently converted a electric motor R/C boat with a O.S. .21 liquid cooled engine. For some f'n reason everytime I drive the thing it dies in the middle of the lake, and I have to swim out to get it! It has got to be something to do with the lack of fuel. Its like theres not enough pressure or something. Also, when I installed the gas motor, I used a direct drive shaft. Do they make a type of clutch to install on these motors???

[Tom Foley]

Make sure you use pipe pressure on the tank to keep a steady supply of fuel to the carb . Adjust the carb so that its very rich to the point that it will not overspeed on the stand , then turn in the needle valve clockwise ,leaner , until it will cleanly take throttle application and then try running it on the water . sounds like its lean to me . Don't keep revving it on the stand with no load or you will take out the con rod for sure .

[moparbarn]

i always use the largest tubing, that will stay on, that i can to run from the pipe to the tank. .21's normally use fairly small tubing, and i have seen oil from the exhaust be thick enough to restrict the pressure to the tank. it won't actually clog the tubing, it's just hard enough to push through the tube that it affects fuel flow. if you are running a tuned pipe, put the pressure fitting in the largest diameter of the pipe. this has only happened once to me, and i think it was fuel/lube related. i agree with tom, though, it sounds lean to me. kinda a pain, because, like tom says, you can't tune on land. make a run, turn needle, make a run, turn needle, repeat as needed. when you think you have it right, run a tank through it and check the glow plug. should be bright and shiny. if the wire is dull or frosty looking, it's too lean. wire should still be coiled and all "in line". if it isn't, it's too lean. glow plugs can be read like spark plugs, just looking for different things. i don't know how you are set up, but raising the tank can help by reducing the distance the fuel has to be lifted. i know it's a fresh set up, but check all fuel and pressure hose for cuts or splits where they go on the tubing and fittings. very easy to get a tear in silicone hoses, and not even realize you did it. have you thought of a fishing rod for boat retreival? a couple of casts, and you stay dry.

AIRWALK

[mike bryan]

allways replace the glow plug first any time you're having any kind of runnability issues.

[LittleProps]

are you running a hopper tank? If not, do you have the fuel tank mounted as high as possible?

[moparbarn]

are you running a hopper tank? If not, do you have the fuel tank mounted as high as possible?

this issue has always confused me. i have run .21 tunnels with and without hopper tanks, tanks low and high, and NEVER noticed ANY difference. stock, modified, pipe or stock exhaust, different props and hulls-nothing. all K&b ob's. is this just a larger motor thing? pressure taps in crankcase, stock in lu housing, or in tuned pipe-nothing. one other thing, i run clunk lines instead of a hard line inside the tank, and mount my tanks with the fittings facing foward. i think the clunk style setup follows the fuel better, and by putting the tank "backwards", the clunk line doesn't have to fold over to get to the fuel. works great for me, i have no lean out issues at the end of a run. if i'm lucky, i get maybe 5 seconds warning before i run out. kinda sucks, because i usually die out in the middle of the pond, but that's when the fishing rod comes in handy. any thoughts?

AIRWALK
TS1-stock 3.5 K&B
TS2-mod 3.5 K&B/pipe & porting
dumas hot shot sprint-3.5 K&B with prather mod kit

[LittleProps]

I have no experience with outboards... i just read alot about people having starvation issues without having hopper tanks, or having the tank up high.

When i was running hardtanks in my nitro boats i always used a clunk pickup, but i always extended the brass tubing all the way so the pickup was always in the back corner that way when it would get low and slosh around in turns it went to the side where the pickup is.

I now only use IV bags but thats for gas. If i could use a bag for my nitro i would.

[moparbarn]

just curious..... , like i said, it doesn't seem to matter on my boats. any progress on that overpowered rigger you were setting up? inquiring minds want to know.

AIRWALK

[Raysoncraft16]

Hey, I've Heard of similar problems to this one. It has to do with the fuel tank being full, and fuel entering the pressure line from the exhaust under corners. Then when the throttle is opened up, the fuel in the line restricts the flow of pressure back into the tank, engine leans up and dies. The fix is a big bodied fuel filter in the pressure line.
It may work, may not, but could be worth a try

[LittleProps]

just curious..... , like i said, it doesn't seem to matter on my boats. any progress on that overpowered rigger you were setting up? inquiring minds want to know.

AIRWALK

Unfortunately no i havent eally done anything with the rigger. I got my new cat and was trying to get it dialed in when i had a slight problem with one of my motors



So right now im just concerned with getting my new motor and getting some time on it before a race i have coming up on the 20th.



The rigger doesnt lack much though. Just need to get the aluminum so i can build the motor mounts, get a micro servo for the throttle and get that all setup and get a new strut, shaft and prop. Im really not in much of a hurry to actually run the boat as the motor is somewhat rare and still very new so i dont really want to lose the motor if the boat comes apart