I have always heard that decarbing gives positive results, but I am trying to figure out why I got negative results--the loss of top end speed. I bought a 1982 Johnson 15hp in 1994. The owner claimed it only had 10 hours on it. If so, it was the hardest 10 hours a motor has ever seen. Nonetheless, good used outboards were hard to come by and the engine has served me well for 15 years. I don't know if the original owner ever decarbed.
Recently, I used a Yahama brand decarb additive. There are two recommended dosages: one for maintenance and one for shock. I used the shock recipe (2 ounces per gallon of gas) and since I also planned on shocking another larger outboard I have had for 21 years, I poured the entire 12 ounce bottle into 6 gallons of gas thinking that I would easily consume it all.
With the boat backed into the ramp, I ran the engine on the treated mixture for several minutes; turned the engine off, and then removed the plugs. The mixture appeared to be working as the plugs showed evidence of carbon being loosened.
One thing I noticed, however, was that there was no smoking. I had always heard to be prepared for a ton of smoke but I was surprised to see nothing more than normal two stroke smoke.
I reinstalled the plugs and repeated the procedure of running the engine and pulling the plugs two more times. I then brought the boat back home with the treated fuel still in the line. (I had heard that if the engine has never been treated to leave the solution in the line to help loosen up the rings more.)
I returned the next day and ran only clean fuel through the engine. I then began to notice that the engine would not run at high speed. I let it run for several minutes on the clean fuel with no change hoping the condition would clear--no such luck. A couple of weeks later I launched the boat to see how the engine would perform on open water. No change--still a major loss of top end.
The engine has been in storage for the past couple of months. I recently tested the compression on the motor and got 75 psi on both cylinders.
What is going on here? Did the decarb mix loosen up some debris and clog my carburetor? The engine mounted fuel filter screen looked fine, as did the additional fuel filter I installed between the engine and gas tank.
The Clymer manual says compression less than 100 psi is not good, but would the decarbing have anything to do with the loss of power? Unfortunately, I never took compression readings before on this engine so I have nothing to compare it to. The engine ran fine before I decarbed.
Is this worth a carburetor rebuild with the thought that I have a clogged jet, or is this engine in need of a ring job?
Given this experience, I have no intention of running that shock recipe solution through my larger outboard but will switch to the maintenance formula and bleed it in slowly.
Recently, I used a Yahama brand decarb additive. There are two recommended dosages: one for maintenance and one for shock. I used the shock recipe (2 ounces per gallon of gas) and since I also planned on shocking another larger outboard I have had for 21 years, I poured the entire 12 ounce bottle into 6 gallons of gas thinking that I would easily consume it all.
With the boat backed into the ramp, I ran the engine on the treated mixture for several minutes; turned the engine off, and then removed the plugs. The mixture appeared to be working as the plugs showed evidence of carbon being loosened.
One thing I noticed, however, was that there was no smoking. I had always heard to be prepared for a ton of smoke but I was surprised to see nothing more than normal two stroke smoke.
I reinstalled the plugs and repeated the procedure of running the engine and pulling the plugs two more times. I then brought the boat back home with the treated fuel still in the line. (I had heard that if the engine has never been treated to leave the solution in the line to help loosen up the rings more.)
I returned the next day and ran only clean fuel through the engine. I then began to notice that the engine would not run at high speed. I let it run for several minutes on the clean fuel with no change hoping the condition would clear--no such luck. A couple of weeks later I launched the boat to see how the engine would perform on open water. No change--still a major loss of top end.
The engine has been in storage for the past couple of months. I recently tested the compression on the motor and got 75 psi on both cylinders.
What is going on here? Did the decarb mix loosen up some debris and clog my carburetor? The engine mounted fuel filter screen looked fine, as did the additional fuel filter I installed between the engine and gas tank.
The Clymer manual says compression less than 100 psi is not good, but would the decarbing have anything to do with the loss of power? Unfortunately, I never took compression readings before on this engine so I have nothing to compare it to. The engine ran fine before I decarbed.
Is this worth a carburetor rebuild with the thought that I have a clogged jet, or is this engine in need of a ring job?
Given this experience, I have no intention of running that shock recipe solution through my larger outboard but will switch to the maintenance formula and bleed it in slowly.
