1996 Mercury 150 EFI 2 stroke - loss of power

[MeanMachine87]

I have a 97 Pro-Line 251 WA w/ twin mercury 150 EFI. Starboard engine runs fantastic, port not so well and I've dumped some serious cash in this thing over the past 2 months and no one seems to be able to fix it.

Background - had new throttle cables put on the engine last year before I stored it. While they were being replaced shop noticed oil injection lines a little weathered. they cut off the bad and reinstalled. Unfortunately they flip the lines and it caused the oil valve to stick open and flood the cylinders with oil. Got that fixed and the motor ran well for about 6 fishing trips. All of a sudden coming back in the port engine started losing power and rpm's were up and down. Changed the plugs and tried it again the next morning - ran decent for the trip out and on the return trip same thing. Took it to the shop and they stated it was the power packs. Had both power packs replaced and now the engine is a dog. WOT on both engines the PORT caps out at 4000. Power is gone. Back to the shop it goes, replace an EFI pack $586 and a trigger switch $188. Still no power and I don't have a clue what to do next. The guy at the shop states he'll come out and go for a ride but I'm beyond frustrated at this point and really need some help.

Could the injectors be spent due to the oil? It seems as though I'm only running on 3 cylinders. One thing I did on my own was start it with the left side wires unplugged...fired right up. Switched and pulled off the right and tried with just the left - it wouldn't start. Could the power packs be bad? Should I try and put the other packs back on? Side note - compression was check in all cylinders and is good, can't be fuel because the kicker and other engine run off the same tank and I always treat the fuel. I did put in new batteries this year, not sure if that could cause an issue. New fuel filter on both engines this year. Thoughts?

 

[MeanMachine87]

Put the old power packs back on and change a filter for the return fuel filter. Fired it up at home and seems/sounds like it should. I'm going to run it a night this week and see if I'm good.

 

[MeanMachine87]

Took the boat for a run tonight with the old power packs and no change. Engine is still a dog. Any ideas? I'm down to ecu or injectors or maybe something else?

 

[Dukedog]

I
One thing I did on my own was start it with the left side wires unplugged...fired right up. Switched and pulled off the right and tried with just the left - it wouldn't start.

Are you sayin' it started with ONLY starboard (1,3,5) plug wires attached and port (2,4,6) completely disconnected? Then wouldn't start at all when tha procedure was reversed? If you have completely lost fire on one bank but have fire on ALL three on opposite bank that leans toward stator or trigger. Do you have an oem manual? If you have tha confidence to do this its an easy test. Your stator wires are red and blue to one switch box and red/white and blue/white to tha other, You can swap these from one to tha other and see if tha problem follows (starting will be opposite bank firing) Keep in mind this is a "backyard" test. Needs ta be done that right way if equipment is available. These things are really hard ta diagnose on a computer though.......An oem manual would be a big help to ya. If nothin' else it would help ya understand more so of what your mechanic is or isn't doin'.........

 

[MeanMachine87]

When I put the original power packs back in I could fire the engine on both banks but no high end power. Good til about 2000 rpms then engine dogs out. I don't have an or manual but will see if I can get one. I have the mechanic going with me for a ride to test it on the water. He said it performed well on the dyno but never had a chance to experience the power difference. I also did some research last night reading other forums and think it could be the stator. But I don't want to keep throwing parts at it without knowing for sure. Not sure if this is important but tach would fluctuate whill running constant speed. Both batteries are new and 750cca. Mechanic said should go with 1000cca but they would be ok. Thanks for the reply I really appreciate it!

 

[wired247]

Where did you get a EFI ECU for $586? I'm assuming its used but thats the sort of thing you'd want to get bench tested by someone with the right equipment before you use it. In any case its more likely to be the high speed coil one one side of the stator than anything else. PM me.

 

[MeanMachine87]

wired247 - sent you a PM. It wasn't an EFI ECU but some sort of EFI module my mechanic stated was spiking when engine was running.

Read something on another forum and was wondering if this could also be a problem. Similar issues with fouling of plugs previously.

Did he test the PORT side temp sensor, and the Intake Air Temp Sensor? These sensors are critical to proper fuel delivery... and if reporting an inaccurate temp (especially a COLDER TEMP) may make the engine run VERY rich.

Also verify thermostat function. A sticking open PORT side thermostat will result in susbstantially rich mixture.

thanks again for the help!

 

[wired247]

Your mechanic basically robbed you. None of the controller boxes are needed and the standard course of action is to disconnect them and see if the problem goes away. If it does then talk about replacing them. The one he likely changed was the idle control box which absolutely is not needed. They dont cost $586 either. The rest of the black boxes are just for alarms or oil injection and dont do squat for how the motor runs. There are no other EFI modules other than the ECU except for the water sensor.

If the motor is under 90 degrees it will go slightly rich. If the TPI isnt set right it will run like crap. If the MAP sensor and/or ECU arent working properly it will run poorly. The port side sensor needs to be working properly. Its a $35 part. The air box temp sensor is also cheap. I would try testing the stator first though as it sounds to me more like a high speed coil problem.

 

[Dukedog]

99% of tha time with power loss with nothing actually visible its gonna be one or combination of these things. switch box boxes, stator, trigger. Once those are determined good or bad ya go from there. Sounds like they were never checked. Most of tha other things mentioned will case a problem that's usually only related to that part. With experience ya kinda know which one goes with which. Not always but ya have an idea from previous problems. If this guy has a "dyno"/knows how ta use it and ya still got a problem I'd be askin' a lotta questions.................

"""""When I put the original power packs back in I could fire the engine on both banks but no high end power. Good til about 2000 rpms then engine dogs out.

Not sure if this is important but tach would fluctuate whill running constant speed.""""

These two things indicate a stator and maybe a rec/reg also without any real way ta test it available!!!

Justa be fair on tha dyno thing. If he is only able to supply tha motor with a hose when makin' a run on it it can't be "loaded' enough ta give ya a "real world" results......

 

[MeanMachine87]

Thanks for the info. Based on your responses it sounds like the stator which is really the last major part aside from the ecu that has been replaced. Mechanic stated it looked fairly new as it may have been replaced within the last few yrs. I've owned the boat about a yr now so who knows when that was checked. Wired I'll give you a call tonight. I appreciate the help and will keep you posted with results.

 

[MeanMachine87]

Quick update - I have a stator on the way. Fingers crossed that's the problem. In the interim since I have twin 150's I'm going to switch the ecu's and see if that's it. My dad is coming out friday for some salmon fishing and if I have to get an ecu from brucato I want to have a little time. Thanks again for all the input i appreciate it!

 

[MeanMachine87]

Switched the ecu's today and no change. Fingers still crossed on stator waiting to get a tool to remove or a mechanic to change it.

 

[MeanMachine87]

Brought to a premier merc guy today. Compression good 105-110, spark test good. Bad was throttle linkage was bent and needs work, also said bottom left cylinder didn't seem to be burning much and maybe a clogged injector. Going to fix throttle linkage first then check the injectors. He did an ohms test on stator and that's good. Feel a little better but hope this guy figures it out!

 

[MeanMachine87]

Brought to a premier merc guy today. Compression good 105-110, spark test good. Bad was throttle linkage was bent and needs work, also said bottom left cylinder didn't seem to be burning much and maybe a clogged injector. Going to fix throttle linkage first then check the injectors. He did an ohms test on stator and that's good. Feel a little better but hope this guy figures it out!

 

[MeanMachine87]

Tested the injector harness. 2.2 ohms for each lead Confirms 1 3 n 5 not running. Bad ground? Bad harness?