RC MAD RAY

Hi all, i have an aquaforce airforce airboat.
to be honest, since i purchased it ive had only 2 decent runs out of it.
this is my problem :
i replaced the original 46 engine purely because it wouldnt run correctly. many posts on here suggest its a very cheap nasty engine so i removed it.
in went a used o.s 46, no problems i fault, this is going to run a treat. how wrong i was !!! it just wont run right, it wants to cut and die at half throttle,will only continue to run if very very rich, which means slow and messy boating ! Im not a happy bunny !
is it over proped though i havent changed prop size ? fuel tank ? or have i just replaced one knackered engine with another one [:@] !!!
thanks
RC MAD RAY

jasperrc

Some more details might help to determine the problem.

What size prop are you running?
How big is the tank?
How far below the engine is the tank mounted?
Have you tried to replace the fuel lines?
What kind and how fresh is the fuel you are using?

If that .46 was tuned for a tank level with the motor, you will have to readjust the carb for the low mounted tank. A fuel pump would fix the problem if tank location is the issue, but I know other boats run in that configuration without issue.

RC MAD RAY

hi, im using the standard 11x6 apc prop, duraglow 10% model technics fuel about 3 months old.
i havent moved the tank at all and its positioned right behind the engine at the same level as the engine.
it seems to want to go, you think you get the mixture right, it does half a lap round the lake then slowly wants to die. bring it in, richen it a bit, send it back out, same thing, half a lap it flys then needs richerning again. i do this untill it runs at a constant steady pace. but i end up with slow and very smokey.
thanks
RC MAD RAY

asmithnc

Mad Ray

Your issues could be a number of things. I remember my high needle (under vibtation) was loose and would lean it self out. Check this.

RS 38-40

My Feedback: (3)

You may also check for pin holes or breaks in the fuel line and/or clunk line . Maybe a plugged clunk ?

crispyspa

Yea.. I was going to say plugged fuel line and/or pin hole in fuel line. It's a good idea to start with a clean tank, then, filter the fuel going into the tank from the bottle AND have a fuel filter on the engine supply line.

Could also be a vacuum leak in the engine itself. Front seal, rear gasket, head gasket or the carb seal ( or a combo of many) could be the cause of the problems.

Or, like Andy said: "my high needle (under vibtation) was loose and would lean it self out"

boatman1

What about the glow plug ? has it been changed ?
is it the break in plug ? try a new glow plug

is this a new motor or used ?

A 11x6 may be a bit much for 10% , try a 10x6 and see if the rpm's come up

Thats about all i can think of

crispyspa

Ah...yes....We tend to overlook the simplest things sometimes. Car won't start? why check the spark plugs if the gas gauge reads "empty" LOL