1994 225hp backfiring

[cj6891]

I have a 1994 3.0l 225hp offshore outboard that is backfiring through what appears to be emission tubes coming from the head. I have changed three bad coils and the backfire occurs at idle but is more prevalent at higher RPM's. It either blows the tubes off or it has blown a hole in a couple. I have checked for spark from all coils and replaced all spark plugs. My next try will be to remove and clean all carbs. I have also already tried to empty carb bowls and connect a remote fuel tank to rule out water in fuel and got the same result. I'm also suspicious of the fuel/oil injection pump. I get an alarm at idle but when I rev the engine the alarm stops but the backfiring is still there. Any help or suggestions would be appreciated.

 

[cj6891]

Re: 1994 225hp backfiring

OK. First I still can't confirm that the tubes that were being blown off are emissions tubes. I was told by a Marine tech that he thought they were oil tubes but I think he assumed that my motor was an Optimax, which it is not. Anyway I have now cleaned the carbs, and re-built the fuel pump. I think that the backfiring has been solved but I can't confirm this because when I started the engine, no water was pumping through the head. I pulled the T-Stat cover to find that it had no T-Stats. I then disconnected the tube coming from the impeller to the T-stats and restarted and no water was moving. I can only assume now that the impeller is bad and have ordered a re-build kit for the water pump. I'll re-post next week after the water pump is fixed and I can confirm if the backfiring has ceased or not. I noticed a noticeable lack of parts for this engine. Most of the high volume parts are available but there are several major components that if they should go bad, the only option is to look for used parts or re-power. I'm a little concerned about this.

 

[cj6891]

Re: 1994 225hp backfiring

The saga continues. Water pump issue has been corrected. The motor is still missing. Also, when you turn the ignition key on after about 15 seconds I get a beep alarm that contiues and does not shut off. I read another post stating that this could be caused by the overheat sensor was bad. Today I replaced the overheat sensor and there was no change. When I turn on the key after about fifteen seconds the alarm returns. I have replaced all of the coils, replaced the overheat sensor, replaced all spark plugs, cleaned all carbs and re-built the fuel pump and still connot resolve the engine missing. I have ran out of options. My next step is to take it to a mechanic unless someone can offer a suggestion of anything else that I can try to solve the problem. This model does have an ECU but I am sure hoping that is not the problem since those are no longer available. I would appreciate any help or suggestions.

 

[Faztbullet]

Re: 1994 225hp backfiring

Those are the bleed lines and they pop off/split or burn thru do to lean crankcase backfire. Open the mixture needles CCW 1/2 turn and see if it helps, if not you may have to rejet the air bleed. Disconnect the 2 blue wire on oil tank as they are know for float failure and causing alarms. If alarm ceases the oil tank needs replaced. Is it missing at idle or all RPMs???

 

[cj6891]

Re: 1994 225hp backfiring

Those are the bleed lines and they pop off/split or burn thru do to lean crankcase backfire. Open the mixture needles CCW 1/2 turn and see if it helps, if not you may have to rejet the air bleed. Disconnect the 2 blue wire on oil tank as they are know for float failure and causing alarms. If alarm ceases the oil tank needs replaced. Is it missing at idle or all RPMs???

Fatztbullet, thanks for the quick reply. I should have mentioned that the backfiring seemed to be resolved when I replaced two bad coils but I also replaced the old lines with new ones so the backfiring could still be occurring during the miss but the new lines are simply holding up better. As for the alarm, I have already tried to disconnect the two blue wires and this didn't resolve the alarm issue, which is what led me to replace the overheat sensor but that didn't do it either. As for the missing, when I start the engine it idles smooth at first start for maybe thirty seconds but then it starts missing and it misses at idle and with increased RPM's. I've replaced the water separator filter and while doing so I dumped the contents into a jar and saw no evidence of water in the fuel. My unit does not have a sensor on the water separator either. All this being said I can adjust the CCW and see if that has an effect on the miss. If anything else comes to mind I would appreciate the input.

 

[Maxz695]

Re: 1994 225hp backfiring

Jmo check the pee stream for tempature if more than luke warm then missing may be caused by water intrusion and the temp is reaching the point where it will sound the alarm. This would be caused by exhaust gasses heating the water to a dangerous level. Could be head gasket or exhaust port problem Just a thought. You say that the water pump was shot so maybe the engine could have overheated. causing warpage of the head as well. Start with a compression check to see if theres any indication of a leaking gasket. You may have to check each cylinder also for timing issues. If internal damage was done then wear of the parts could have cause timing of one or more cylinders to be off.

 

[Faztbullet]

Re: 1994 225hp backfiring

Start with a compression check to see if theres any indication of a leaking gasket

Sorry but this engine does not have gaskets ..it uses o-rings and can withstand a lot of overheats before failure.
Check the shift interrupter switch on the shift bracket as this kills cylinder 2.4.6 and will cause a miss and low power. Also recheck the heat sensor by disconnecting wires and retesting ,if it still sounds it possible the TPS has failed as manual states it sound horn 15 seconds after ECU detects failure in either sensor.

 

[cj6891]

Re: 1994 225hp backfiring

Sorry but this engine does not have gaskets ..it uses o-rings and can withstand a lot of overheats before failure.
Check the shift interrupter switch on the shift bracket as this kills cylinder 2.4.6 and will cause a miss and low power. Also recheck the heat sensor by disconnecting wires and retesting ,if it still sounds it possible the TPS has failed as manual states it sound horn 15 seconds after ECU detects failure in either sensor.

OK in an effort to find where the alarm was coming from I went through the following with ignition on and alarm activated:
1. Disconnected both leads from oil tank sensor. No change. Plug wires back in.
2. Disconnected all three leads on overheat sensor. No change. Plug wires back in.
3. Disconnected the connector on the TPI. Alarm silenced and then returned about 15 seconds later. I moved the throttle arm to cause movement in the sensor and the alarm silenced but returned after about 15 seconds and then moving the throttle arm had no effect after that.
If I turned off the key and turned it back on I can recreate this every time. Alarm activates disconnect TPI and alarm goes off and comes back on in 15 seconds. Move the throttle arm on the carbs and alarm silences but returns in 15 seconds and this only works once in the cycle.
So am I to assume that my TPI is bad? I want to be sure as this is an expensive part to throw at it without knowing. Also, can a bad TPI cause the miss firing that I am seeing?

Thanks for the help.

 

[Faztbullet]

Re: 1994 225hp backfiring

The TPI could cause a miss if timing was retarded to much and plugs was fouling but thats way out there. Can you narrow miss to a certain cylinder/s with timing light? Disconnect throttle cable and see if timing advances when reved up also....

 

[Jwhitchard0607]

Did you ever fix this? Mine is doing the same exact thing. If so where did you find the parts? Seeing how everything for my motor seems to be discontinued. Also did yours have a 12 pin plug on the stator?

 

[racerone]

Start a new thread for help today.