Nitro fuel tank placement and flooded engines (question)

[Doug Brumfield]

Interesting.. I have done some porting work on 1:1 stuff, and even modified some carbs to clean up air flow.. .. but it never would have occured to me to delete the low speed needle... beyond removing the needle, what else is done? anything? (in regards to the low speed delete, not the entire engine mod process, I'm not ready to go there with the boats yet) I assume the screw is kept, just the point itself removed?

I would even go out on a limb and say the venturi effect would be its most efficient without the obstruction..

Probably especially important once an engine has been modded to pump more air..

as far as more of a fuel-air 'hit' when you crack the throttle, thats mostly for the start? Seems in most of the race videos their isnt much lifting going on in the turns for most boats..

 

[Grimracer]

I have a vegas deuce boat, all stock save removal of the tigre drive and the addition of a proper backplate.

I have had problems from day one with the engine flooding badly (you can watch the fuel siphon from the tank into the engine and ultimately into the hull)

I have in the past raced gas trucks and touring cars, and I know how to tune well enough that my stuff always started right up, ran good and maintained good temps..

The tank in this boat, if you arent familiar with it, resembles an 1/8th scale buggy tank, and is of questionable quality.

The carb is composite, the engine is a supertigre .18

I have elavated the rear of the boat a foot (tanks in the front) and only filled the tank halfway after running it all the way out of fuel, and it still floods when I try to start it, to the point that the cyl is full of fuel.

Once running it runs alright, though it seems to be just a hair ragged at idle, and economy seems off a bit (my buddies proboats with smaller tanks run longer)

I am planning on replacing the fuel tank (I actually tried a sullivan at one point but it didnt fix the problem) and the engine (or at least the carb)

My question is, how critical is tank level in regard to engine? If the top of the tank is higher than the carb, but the pickup is below it, shouldn't I be good? Is this more likely a carb issue? any ideas whats going on? I know of other people that have this boat without these issues, so I tend to believe something somewhere has to be amiss.

Thanks for looking, sorry so wordy.

Doug,

As the others have stated, syphoning is not uncommon in our boats.

One thing that can be hard for a RC car or airplane tuner coming over to RC boating is how the motor idles and what that looks and sounds like in an RC boat. Trust me when I say.. if its got what “you know to be a great idle”… ITS LEAN for RC boating. WAY LEAN. You want a VERY FAST idle and it’s got to be fat.. not want you are used to. We don’t have to worry about the motor “Stepping down”.

Another important tid-bit is temping an RC boat engine. I guess you can use a “temp Gauge” but truth is it’s not very effective. You cannot bring the boat in safely idling and “any” water that was in the cooling chamber is now gone. Learning to read the plug is way more important in RC boating then Temping!

Also… just so you know.. the ST18 is a thirsty little buggar..

Because we don’t run our boats inverted.. at least most of us….lol.. The tank position albeit important is not “Critical” If one could lower the tank to the point the top of the tank was lower than the carb it would not syphon and run just fine but in most cases that cannot be done.

Grim

 

[Doug Brumfield]

Agreed, the boat doesn't get used like a car.. with the ST I had there is no way the idle mixture couldve been too lean.. needle was faulty /broken.. boat ran fine, but because of that I had a fast idle, and fat mixture.. so no problem there I actually had it idled up at the controller, and brake would close the throttle the last bit and kill it as I brought it in.. may put a 3rd channel kill on it at some point.

I think had I realized what was going on, I could've worked around it (or fixed it)

Im pretty sure the Vegas should be dialled at this point.. Just ordered a UL1 as well, and the upgrade prop.. might even have to do a revolt once they are out and any bugs sorted out.. I've found having several boats is a good idea if you are spending an afternoon at the pond.. another difference between cars and boats.. I can race 1 car all day and be perfectly fine with it.. 1 boat isnt nearly enough.