Doodle Bug
Well-known member
When looking for a solution to a problem, I liked to write down the problem in detail and make a list of what could be causing the problem and all possible solutions.
After looking over my notes I thought the information might be of interest to other airboaters. If you see something that looks familiar, your right, I stole most of the information from you guys. Please don’t get mad. Think of it as a compliment.
I am not a mechanic and until this summer I did not know it was possible to have a carb/auto/engine not diesel. If you see something that I said (or copied) is wrong, or you have other information, solution or ideas, I would like to know so we can all benefit.
Dieseling is caused by having a combination of air, gas and hot spot’s in your combustion chambers when you turn off your engine.
SOLUTION:
1. To cool hot spots in your combustion chambers you need to:
a. When coming to a stop, let the engine idle down for 30-60 sec. or more to help cool the cylinders down before turning off the engine. This also helps to keep the valves from warping.
b. In hot weather remove thermostat or use a 160* thermostat.
c.* Install a time delay kill switch with an emergency shutdown to keep the engine running for 30-60 sec. to insure proper cooling. (For the person who can’t remember to do it all the time.)
2. High rpm when idling:
a. Run the lowest rpm when possible to maintain a smooth idle.
b. Make sure the idling screws are adjusted correctly.
c. Use an idle solenoid to close the throttle blade all the way when you shut off the engine.
d. Use a hand throttle control cable to insure the lowest rpm’s and maintain a smooth idle.
3. Air getting into the combustion chamber:
a. Vacuum leak.
b. Air coming down the idle system of the carburetor (this is normal for the proper operation of the idle system).
c. * Install a air shut off device to the idle system intake on the carburetor.
d. * Install a Tetrafluoroethane gas injection system to starve the engine of air when ignition is turned off. I tried this and it does work.
4. Gas vapor getting into cylinder.
a. Inertia of the prop keeps the motor turning and the vacuum (low pressure) of the motor keeps pulling fuel thru the idle system and keeps
the motor running. * Solution, disconnect prop.
b. * Add a electrical valve to open the vacuum to outside air, at the same time you remove ignition.
c. Gas pump pressure to high.
d. Turn off gas pump 30-60 sec. before shutting off engine to remove pressure from gas line.
e. Add a electrical gas shut off valve just before the carburator.
5. Ignition timing:
a. check timing at idle.
b. Disconnect vacuum advance and use a toggle switch on ignition for easier starting.
c. If advancing the timing makes for easier starting and the ignition is turned off. ( I don’t understand how this would affect the dieseling. Does anyone have an opinion?)
* Possible, but may not be practical. Items may have to be designed and built.
After looking over my notes I thought the information might be of interest to other airboaters. If you see something that looks familiar, your right, I stole most of the information from you guys. Please don’t get mad. Think of it as a compliment.
I am not a mechanic and until this summer I did not know it was possible to have a carb/auto/engine not diesel. If you see something that I said (or copied) is wrong, or you have other information, solution or ideas, I would like to know so we can all benefit.
Dieseling is caused by having a combination of air, gas and hot spot’s in your combustion chambers when you turn off your engine.
SOLUTION:
1. To cool hot spots in your combustion chambers you need to:
a. When coming to a stop, let the engine idle down for 30-60 sec. or more to help cool the cylinders down before turning off the engine. This also helps to keep the valves from warping.
b. In hot weather remove thermostat or use a 160* thermostat.
c.* Install a time delay kill switch with an emergency shutdown to keep the engine running for 30-60 sec. to insure proper cooling. (For the person who can’t remember to do it all the time.)
2. High rpm when idling:
a. Run the lowest rpm when possible to maintain a smooth idle.
b. Make sure the idling screws are adjusted correctly.
c. Use an idle solenoid to close the throttle blade all the way when you shut off the engine.
d. Use a hand throttle control cable to insure the lowest rpm’s and maintain a smooth idle.
3. Air getting into the combustion chamber:
a. Vacuum leak.
b. Air coming down the idle system of the carburetor (this is normal for the proper operation of the idle system).
c. * Install a air shut off device to the idle system intake on the carburetor.
d. * Install a Tetrafluoroethane gas injection system to starve the engine of air when ignition is turned off. I tried this and it does work.
4. Gas vapor getting into cylinder.
a. Inertia of the prop keeps the motor turning and the vacuum (low pressure) of the motor keeps pulling fuel thru the idle system and keeps
the motor running. * Solution, disconnect prop.
b. * Add a electrical valve to open the vacuum to outside air, at the same time you remove ignition.
c. Gas pump pressure to high.
d. Turn off gas pump 30-60 sec. before shutting off engine to remove pressure from gas line.
e. Add a electrical gas shut off valve just before the carburator.
5. Ignition timing:
a. check timing at idle.
b. Disconnect vacuum advance and use a toggle switch on ignition for easier starting.
c. If advancing the timing makes for easier starting and the ignition is turned off. ( I don’t understand how this would affect the dieseling. Does anyone have an opinion?)
* Possible, but may not be practical. Items may have to be designed and built.
