Hello. I have a Johnson J25RSTC, 25hp, 2 stroke, outboard tiller I bought new off the showroom floor back in 2003.
About 1 month after breaking in the motor per Bombardier's specifications an interesting, chronic, and now extremely aggravating problem arose.
From a cold start, if I run the motor at full throttle, within 5 minutes it will start chugging. Along the lines of a severe misfire or pre-detonation. Maybe even along the lines that the fuel pump isn't delivering enough fuel. It's hard to describe, but when this happens, the motor bucks so hard that it will actually pop up out of the water enough to engage the shallow-drive tilt. After the engine's hot, if I run it wide open, it will take 1.5 - 2 minutes to exhibit the same behavior. I can run the motor in short bursts at full throttle, but never sustained.
Oddly enough, if I run the motor wide open just long enough to get on plane and then very, very slightly back off the throttle until I hear a slight reduction in RPM, it will run problem-free all day.
When the motor acts up, what usually does the trick is to hit the kill switch, wait 5-10 seconds, fire it up, put it in reverse, and run the throttle wide open for a couple seconds.
Idling and low-speed are completely normal. The only time I need to restart the motor while fishing is if I hit the kill switch or, as has happened on occasion, gotten stupid and ran out of gas.
Things I've done:
1.) Took it to 3 different shops. Each one claimed to have fixed the problem. One said a temperature sensor, another said rev sensor, don't recall what the other one said. However, since none of them ever fixed the problem and I figured out a workaround, I've not bothered to take it back to any shop.
2.) Replaced spark plugs.
3.) Tore apart the entire fuel system. Cleaned and reassembled it. Checked all hoses and Ts - no leaks. At the same time I replaced the zip ties Bombardier used at every junction of vacuum and fuel lines with hose clamps.
4.) I've ran the motor with the cowling both off and on. That makes no difference.
5.) Held my hand under the "pee jet" while running the motor. The water's warm, but never gets to a temperature that's uncomfortable or where I had to take my hand away.
6.) Re-routed the fuel line to the filter so it's now on the opposite side of the power head. Before it was routed in such a way that it was leaning against the heat exchanger.
The first and last tanks of the year I dump in 10 ozs of Seafoam and adjust the oil content appropriately.
I have a dedicated 5-gallon mixing can to ensure, as much as possible, a consistent 50:1 mix.
The last tank of the year gets run until it and the engine are dry.
At the end of the season, I let the lower unit drain for 1-2 days, then fill it with fresh grease.
Engine is stored outdoors. I live in southern MN, so it sees temps anywhere from -40 to 95.
I'm no mechanic, but that this point I'm positive this behavior has nothing to do with temperature.
Any suggestions as to what to do next (at this point I'm ready to dump this motor in the lake and go buy a new 4-stroke Honda) are greatly appreciated.
Thank you.
About 1 month after breaking in the motor per Bombardier's specifications an interesting, chronic, and now extremely aggravating problem arose.
From a cold start, if I run the motor at full throttle, within 5 minutes it will start chugging. Along the lines of a severe misfire or pre-detonation. Maybe even along the lines that the fuel pump isn't delivering enough fuel. It's hard to describe, but when this happens, the motor bucks so hard that it will actually pop up out of the water enough to engage the shallow-drive tilt. After the engine's hot, if I run it wide open, it will take 1.5 - 2 minutes to exhibit the same behavior. I can run the motor in short bursts at full throttle, but never sustained.
Oddly enough, if I run the motor wide open just long enough to get on plane and then very, very slightly back off the throttle until I hear a slight reduction in RPM, it will run problem-free all day.
When the motor acts up, what usually does the trick is to hit the kill switch, wait 5-10 seconds, fire it up, put it in reverse, and run the throttle wide open for a couple seconds.
Idling and low-speed are completely normal. The only time I need to restart the motor while fishing is if I hit the kill switch or, as has happened on occasion, gotten stupid and ran out of gas.
Things I've done:
1.) Took it to 3 different shops. Each one claimed to have fixed the problem. One said a temperature sensor, another said rev sensor, don't recall what the other one said. However, since none of them ever fixed the problem and I figured out a workaround, I've not bothered to take it back to any shop.
2.) Replaced spark plugs.
3.) Tore apart the entire fuel system. Cleaned and reassembled it. Checked all hoses and Ts - no leaks. At the same time I replaced the zip ties Bombardier used at every junction of vacuum and fuel lines with hose clamps.
4.) I've ran the motor with the cowling both off and on. That makes no difference.
5.) Held my hand under the "pee jet" while running the motor. The water's warm, but never gets to a temperature that's uncomfortable or where I had to take my hand away.
6.) Re-routed the fuel line to the filter so it's now on the opposite side of the power head. Before it was routed in such a way that it was leaning against the heat exchanger.
The first and last tanks of the year I dump in 10 ozs of Seafoam and adjust the oil content appropriately.
I have a dedicated 5-gallon mixing can to ensure, as much as possible, a consistent 50:1 mix.
The last tank of the year gets run until it and the engine are dry.
At the end of the season, I let the lower unit drain for 1-2 days, then fill it with fresh grease.
Engine is stored outdoors. I live in southern MN, so it sees temps anywhere from -40 to 95.
I'm no mechanic, but that this point I'm positive this behavior has nothing to do with temperature.
Any suggestions as to what to do next (at this point I'm ready to dump this motor in the lake and go buy a new 4-stroke Honda) are greatly appreciated.
Thank you.
