Mercury 92 175 EFI XRi 2.4 L power loss?

[H2Okie]

Trip before last opened the throttle to get get my boat up on plane and then RPM's were climbing and then the engine stumbled without stalling and then seemed normal after I backed the throttle off to idle . After that point for the rest of the day when trying to get my boat on plane RPMs seemed to be limited around 2000 and took awhile to get planed off . Once on plane I took the engine up to 4500 RPM and I think I could have got normal full speed but it just didn't sound right and I was concerned about stressing the motor from a yet unknown problem . I promptly put it in the shop and the diagnosis was a disolving fuel line internal liner clogging up the fuel filter/water separater which the mechanic replaced . I took the boat out yesterday and when I went to put it on pad same problem (stuck on 2000 RPMs and trouble planing off. ) Looks like the new mechanic is not as good as the guy that has always worked my boat since new and has been awesome .
Once on plane I went up to 5200 rpms pretty easy for a second but it still doesn't sound right like a moving intermittant miss .
I just checked the resistance of both of the switch boxes and they are up to factory specs resistance wise (all 1180-1190 ohms ). I also checked the resistance for the red and blue pairs from the stator and their resistance is also OK with factory specs (blues to ground 3510/3760 ohms) Reds to ground both 106.5 ohms .
I just put an induction timing light on each plug wire and cranked the engine over and every plug seems to have a steady pulse of plug firings .
Another thing I noticed that was kind of strange - whenever the engine is running and switched off the tach has always settled on 1000 RPMs . Ever since this trouble started the tach has been settling on 2000 RPM when off . Electrical shift due to ground issue? Next I am going to bring a meter and try some live on the water testing at various load to see if I can pin anything down .
This problem sound familiar to anybody ?

[toyomirage02]

i had the same prob on a 200 efi was on a mako bay boat a week ago chased **** all around the boat finally the last piece of fuel line 2 ft long from the filter to the tank was comin apart on inside,drove me nuts.could be as simple as a plug fowling out.or ya might have alittle bad watery fuel

[rock]

Check compression.

Rock

[H2Okie]

I should have mentioned while in the shop and found the disolving fuel line they ran a compression check and listed all 6 cylinders @ 120 #s

[toyomirage02]

no problem with that comp # at all

[rock]

I suggested that cuz of the amount of motors I have seen that "lost power" but still ran. Some of the efi units have a cone shaped filter in the hose leading from the vst to the bottom of the electric pump. I have seen that thing plug up and cause havoc.
You have good compression and you said you checked and have good spark. That leaves fuel. If you can get a set of noid lights you can check the injectors are getting a signal. Do all 6 plugs look the same? Differences could point to a specific cylinder. I would also check the stator. The high side could be going out. A stator failure will often allow motor to run flawlessly up to a certain rpm (usually 2500 to 3500) then fall on it's face (since your tach has changed you may not be getting the reading you think you are). I have also seen them finally accelerate after laboring at the lower rpm for a second. These are easy things to check.

Rock

[simplyorange]

if you had a fuel problem you should probably clean all of it, pump, filters, injectors etc.

[H2Okie]

Thanks for all the responses guys . I have two gas tanks on the boat and typically run on the port side tank with the starboard side empty . I 'll have to gas up the starboard side tank and try running on that tank to see if the problem clears up . My engine has only had Chevron midgrade run thru it since new and the shop changed the fuel/water spin-off filter and checked the screened filter clean on the right side of the ECU . I noticed the tach is now back at 1000 RPMs with the key off instead of the 2000 RPM it had been stopping at . I was verifying all the engine ground wires tight and noticed some powdery white corrosion on some ring terminals on ground wires on top of the engine block . One of those black wires goes to the mounting plate all of the spark coils are mounted on and all of the negative side spark coil wires are bonded to this mounting plate .
A bad connection on that one wire could affect all six spark coils . I cleaned the corrosion off of the ring terminals and the surface of the engine block they connect to . Maybe the tach changing back is just a coincidence , I'll have to see next weekend when I get the boat back out .

[H2Okie]

Before my latest trip to the lake I put a half tank of new Chevron in the spare tank on the way to the lake and launched fired up the engine with no trouble with the fuel tank I had been running when the trouble started . After the engine was warm I opened the throttle and tried to plane off wallowed around stuck at 2000 RPMs before it finally got out of the hole and planed off .
I shut down and switched over to the spare tank containing the known good fuel and unfortunately
the motor responded the same way so it is not the gas thats the problem .
In looking over the motor I noticed something I missed before . It appears there may be slight leakage out of the RH side of the divder plate because its damp with what looks like a gas/oil /carbon mixture seeping out between the engine block and divider plate gasket .

would this leak be a possible indication of why I have a power loss problem now?
I just ordered a DVA peak voltage adapter and a fuel injector pump test gauge so I can start working thru the ignition and fuel system to find the problem .

[Go Time]

Its the stator...high end

[simplyorange]

check for vacuume hose leaks too. then i would agree with checking the stator.

[rutro]

Yes check all your bleed lines. I just got through replaceing all my fuel line because of same problem on a 2.4 carb motor. When it started acting up it sneezed a few times and I guess thats when it poped one of the bleed lines off, I thought that was the only problem till I took it out again. It's probably something simple and you'll kick your self when ya find it!!!! But serriously replace all the fuel line, filters, aand check anything else that has to do with fuel delivery.

[nerve damage]

Did you ever figure it out? I have the excat same problem!!!!!
I pulled the power head off to freshin it up over this winter an I found that someone had replace one of the caps for where the bleed lines would go with a hose an a screw behind the switch box bracket has falling off. Could this be all thats wrong with it?

Thanks Pete

[H2Okie]

Did you ever figure it out? I have the excat same problem!!!!!
I pulled the power head off to freshin it up over this winter an I found that someone had replace one of the caps for where the bleed lines would go with a hose an a screw behind the switch box bracket has falling off. Could this be all thats wrong with it?

Thanks Pete

Yes I did after checking out all of the electrical ignition components with everything passing I moved onto the fuel lines , fuel pump , etc .
I found a bad injector by disconnecting the harness connecter and ohming out the injector pairs 1&2 , 3&4, 5&6

[nerve damage]

Yes I did after checking out all of the electrical ignition components with everything passing I moved onto the fuel lines , fuel pump , etc .
I found a bad injector by disconnecting the harness connecter and ohming out the injector pairs 1&2 , 3&4, 5&6

Thanks H20kie
I just need to fine some info on the values now then :cheers:

Thanks Pete