Mercury 175 XRi ECU on 200 EFI

[killerpirate]

Hi Guys,

Ive been encountering issues with my 200 efi lasts weeks. It suddenly started to idle rough and i lost a small amount of top speed (about 2 mph). Furthermore the engine has lots of power and feels strong.

Replaced/rebuild: Pulse fuel pump, VST, reeds (boyensen), checked spark on plugs.

Today i swapped the 200 ECU with a 175 XRi ECU. I did test in on the hose and it appears to idle fine suddenly. Again, this was on the hose and not in the water.

My question: would a faulty ECU be able to create such a situation where it idles like Sh*t, but still works great on other RPM's?

Also: Whould it be okay to go for a test run with a 175XRi ECU on the 200 Block? Would it be lean? Or would it be okay in practice?

Thanks!

[LakeFever]

have you checked the tps and done a link n sync?

[tlwjkw]

Hi Guys,

My question: would a faulty ECU be able to create such a situation where it idles like Sh*t, but still works great on other RPM's?

Also: Whould it be okay to go for a test run with a 175XRi ECU on the 200 Block? Would it be lean? Or would it be okay in practice?

Thanks!

yes, it could..........

run it like ya stole it...... you'll never know till ya try it... merc was not to "hands on" with they're quality control with tha ecu's, soooooooooo......................

don't think they understood tha word "lean" with anything they (production) built except some ecu's that had a lean spot at certain rpms.. again tha QC process!

[killerpirate]

So it would be fine to taken it for a testrun?

Did not test the tps, cause i dont have the test harnass. Been thinking about doing it eithout the harnass, but i cant think of any way to reach the terminals :)

Sync & Link, that is the sequence where you set all the timing and throttle valves to spec, correct? Section 2c-10 to 2C-18 of the service manual?

I have this manual: https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.hedges-uk.com/boat/Merc/outboards/2-stroke/2-stroke/135-150-175-200/135-150-175-200%2520With%2520Serial%2520Numbers%2520United%2520States%2520-%25200G960500%2520and%2520Above.pdf&ved=2ahUKEwiyxPXdlf6HAxWv2QIHHd-WATQQFnoECBYQAQ&usg=AOvVaw1rQ84IyK-5yhx4Y5LSRv_u

[tlwjkw]

that one is for tha 2000 ('lectronic motors) and up.. what year is yours?

[PanRonnie]

So it would be fine to taken it for a testrun?

Did not test the tps, cause i dont have the test harnass. Been thinking about doing it eithout the harnass, but i cant think of any way to reach the terminals :)

Sync & Link, that is the sequence where you set all the timing and throttle valves to spec, correct? Section 2c-10 to 2C-18 of the service manual?

I have this manual: https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.hedges-uk.com/boat/Merc/outboards/2-stroke/2-stroke/135-150-175-200/135-150-175-200%2520With%2520Serial%2520Numbers%2520United%2520States%2520-%25200G960500%2520and%2520Above.pdf&ved=2ahUKEwiyxPXdlf6HAxWv2QIHHd-WATQQFnoECBYQAQ&usg=AOvVaw1rQ84IyK-5yhx4Y5LSRv_u

To test idle yes, full throttle no
unless You add an adjustable pressure regulator to pump up the pressure
And having an egt gauge with alarm is really great

https://youtu.be/_s_7rLZsgdw?si=sbAw0QyY3rzCwsvz

[tlwjkw]

all that fancy 'lectronic stuff wasn't even on tha drawin' board when we used "real world" testin''... jus sayin'.................

ecu doesn't have anything ta do with fuel pressure anyway.......... thats all on tha pump and regulator..... it jus tells tha pump when ta run.

[PanRonnie]

all that fancy 'lectronic stuff wasn't even on tha drawin' board when we used "real world" testin''... jus sayin'.................

ecu doesn't have anything ta do with fuel pressure anyway.......... thats all on tha pump and regulator..... it jus tells tha pump when ta run.

It has when you use a 175 ecu on a 200

[tlwjkw]

we will have ta disagree on that.. any ecu 150/175/200/promax, all have tha same pump circuit... it turns 'em on or turns 'em off..... tha 175 is not special..........

bobby v. has ran every combination possible with horse powers and ecu combinations.. they usually ran tha same no mater what was on what... if it was bad on one it would be bad on tha other and vice versa.... there was never a lean or fat change at all.

jus remembered one thing though.. some would show a slight change in max rpm... but not enough ta mater much for a production motor.......

[PanRonnie]

I don't mean the pump running circuit, i mean the fuel curve inside the ecu for the designated horsepower
You might get away with the 25hp difference but it could also mean a melted piston

https://youtu.be/7XTil1msFIc?si=gfPnE35hEJ7r8GwE

This is how that looks, really ruines your day
In this case it was aftermarket injectors deviating to much but the idea is still the same
Having a horn scream at you when your egt's are to high is ver good to have

[LakeFever]

I have an xr6 150 I bought from a bass boat guy who ran a 200ecu on for years no issues. He didn’t even know it wasn’t the right one for his motor he didn’t service it himself this was installed during maintenance when what sounds like a driver issuer on his factory ecu failed. Said it ran the same.

I’m about to try a 225 ecu on a 200 and see how that goes

[PanRonnie]

That would be putting a richer ecu ( more horsepower more fuel ) on a lower horsepower engine needing less fuel
You might loose some horsepower from the richer curve but it is not going to brake it

[tlwjkw]

after years and years and years of runnin' justa 'bout anything on anything between myself and bobby neither of us have ever "melted" a motor down because of a lean condition.......... jmo.

[tlwjkw]

That would be putting a richer ecu ( more horsepower more fuel ) on a lower horsepower engine needing less fuel
You might loose some horsepower from the richer curve but it is not going to brake it

has nothing ta do with pressure which i thought you were sayin' tha ecu could regulate....

[LakeFever]

Very true. Using a bit more fuel would probably not even register. I am blown away how much fuel my 200 uses at 3/4 throttle, vs full throttle. It’s not a little more it’s probably five times more fuel at full throttle. I guess that’s how it goes when using enrichment as the rpm limiter. Crazy

I also feel the differences between the 2.5 fishing motors be it 150/175/200 are more about stickers than actual differences in the motors themselves. Think about it. All the fishing motors except for the F have four or five petal front half’s which are the same size intake openings. The biggest differences I can see is in the block castings are between the small and big chests. EE is a small chest yet runs a 200 ecu. CC looks to be the same block with reliefs in the sleeves. FF is different sleeves and bigger chest yet runs great on the same 200ecu lol. Promax 225 is a seven petal though so my thinking is it is calibrated richer. Among the four and five petal motors they are so very similar I can see how any ecu would probably run fine on any 2.5
variant

[tlwjkw]

I have an xr6 150 I bought from a bass boat guy who ran a 200ecu on for years no issues. He didn’t even know it wasn’t the right one for his motor he didn’t service it himself this was installed during maintenance when what sounds like a driver issuer on his factory ecu failed. Said it ran the same.

I’m about to try a 225 ecu on a 200 and see how that goes

it may or may not go to tha limiter... guess you can find out for us......:)

well, it will depend on whatcha runin' i guess, also........:reddevil:

[PanRonnie]

The are actually 2 pressure's between the 2 VST,s
The one with the high pressure pump outside the VST has a lower pressure that the one with the high pressure pump inside the VST
That already could make a difference
As my promax 225 were ported van ackeijlen already told me the orginal pressure was insufficiënt
So i actually started rich but it was still not enough when running the original promax ecu's
I have to run 48 psi on the A6 and close to 50psi on the A32

[LakeFever]

it may or may not go to tha limiter... guess you can find out for us......:)

well, it will depend on whatcha runin' i guess, also........:reddevil:

its a spare haven’t done anything with it yet. Going to build an FF clone to what I have now just to have as a back up and then take the EE and cut it to 260 porting. Will be a brucato for that one. Might brucato this FF I’m running now if the a17 promax box doesn’t work out well.

[tlwjkw]

The are actually 2 pressure's between the 2 VST,s
The one with the high pressure pump outside the VST has a lower pressure that the one with the high pressure pump inside the VST
That already could make a difference
As my promax 225 were ported van ackeijlen already told me the orginal pressure was insufficiënt
So i actually started rich but it was still not enough when running the original promax ecu's
I have to run 48 psi on the A6 and close to 50psi on the A32

ya still had ta maybe change tha pump and tha regulator ta achieve those pressures... all tha ecu supplied was tha fuel curve necessary ta support all tha work done to it....

we're talkin' 'bout plain 'ole production motors..

tha one outside actually can run at two speeds (courtesy of tha ecu)... but thats with tha 'ole timey analog ecu's....

[tlwjkw]

gettin' way off topic so i'm done.. ya'll have a very good Sunday....................:D

[PanRonnie]

Yep i have deleted the VST's and run the custom pressure's
But a production 200 with a production 150 ecu?
Well i would like to see that video
You never melted a piston, i had 2 melted with the original A17 ecu my 98 promax had on it
There was a lean spot in it, somebody in Amsterdam had the same engine exact same issue same ecu
The bulletin to replace the A17 to the A32 said it was due to poor fuel quality but older engines were just fine
I am just saying it could happen not that it is going to happen

[LakeFever]

I believe anyone who’s run two strokes for any amount of time ( save for the premix v4 cross flows that never die ) we’ve all melted two strokes down. I did read that the a17 was the second leanest promax box but with a four petal 200 my hope is a goldilocks effect. Just right

Failing that I do have an adjustable fpr so I can mess with that a little and see how it works. Anyways poor op we have taken this thread off the rails here haha. Info overload

[killerpirate]

Thanks for the replies guys!

What about a 200XRi vs a 200EFI? Is there any difference in ECU's there?

[LakeFever]

Thanks for the replies guys!

What about a 200XRi vs a 200EFI? Is there any difference in ECU's there?

xri is what the early efi motors were called. There are quite a few different ecu part numbers out there. Some were better than others. Two types as well there are analogue and digital although they look the same from the outside. They do fail from time to time, some can be repaired, some can’t. There’s a business called Simon performance who specializes in ecu repair and there is also Brucato who sells replacement units. Brucatos typically make more power and get better fuel efficiency especially if you run wide open all the time.

If you look on the side of your ecu there should be a sticker there with some numbers on it. A8 or something along those lines. Most of use use the A plus whatever number beside it to describe the type. If you want to replace your ecu take a look at your number and put up a wanted ( ISO ) ad for that model you’ll probably get some quick replies. Or look on fleabay or other related online sales markets.

[killerpirate]

Alright, i did some testing today

I found a new ECU in my area, but before i buy it, i found something strange.

Today i tested motor again on the hose. I put on a 175 EFI (older motor) ECU on it, and it seems to idle pretty good (unlike last time) as far as you can hear it on the land. Then i removed the 175ECU and put back the 200 ECU on the motor. Exactly the same. Seems to idle ok.
Then i started to remove the spark plugs cables 1 by 1.

Right bank: as soon as i remove 1 cable, it started to idle like ****.
Left bank: when i remove a cable, nothing happens. It just idles the way it does (pretty good). I even removed all 3 left bank plugs and it keeps running the same. When i reconnect 1 wire, it does get a very small 'bump', but nothing really changes. When you remove the cables, you can hear the arcs jumping, so they got spark.

So i put on a new switch box (the top one). No changes what so ever. Swapped the ECU's a couple of times to verify it didnt change.

Took the plugs out, and all 6 off them are a little bit wet, nothing special in my opinion.
I understand that when the engine has no back pressure, its difficult to test.

Also i disconnected the idle stabilizer, which had 0 influence on the way it behaves (i checked timing, and it is approx 0. (VST spec says should be 4atdc), but this test was just to verify that idle stabilizer wasnt influencing.

I have no idea what to make of this. Whats next? Stator? Voltage regulators? I dont see how the voltage regulators can create this effect..

i will try to find a TPS test harness in the mean time.

[LakeFever]

Ecu controls fueling. Stator, trigger, switch boxes control spark. Those timing modules are notorious for taking out motors. Seeing as the age of all this and especially after personally melting one down I suggest deleting all the black boxes and modules. Manually set the timing to 23 degrees. Delete oil injection and run premix.

[KIRCHNER]

pulling the plug wires off, on the hose says nothing. i have 3 v6, it seems like something is off, the way the motor reacts, but trust me, launch it and take off. itll be running fine. dont ask

[KIRCHNER]

i put two single strand copper wires in the female sockets in the plug bend em over plug connector back together. small single strand 24G? connnect volt meter dont forget to unplug port head sensor. if meter goes -, reverse polarity.

[OnPad]

The starboard coils power is routed through the ecu for injector timing. The port bank isn't. Maybe you drop a pair of injectors when you unhook a plug wire at starboard bank?? Possibly it doesn't register a pulse from the coil going to ground???

What about the map sensor? Your symptoms sound similar to a few old threads read, where a map was bad. Older manual sez a vacuum can be applied to hose and it should create a lean condition altering engine operation,. If no change occurs map sensor is not functioning. Map can also be checked with a efi tester.

My 200xri runs rich, I wouldn't hesitate to try a 175 ecu, but my 150 Supermag plugs come out paper bag colored. Idk if it would have enough fuel running a 200? I remember someone (probably Bobby v) saying he rode mismatched ecu's, and liked the 150 ecu. If I remember right he said "might surprise you". I'm thinking it might,.. when it blows up, or when it runs 5mph faster.

A couple small strands of wire can carefully be sandwiched into the tps plug for calibration, if you can't find a adapter.

[tlwjkw]

My 200xri runs rich, I wouldn't hesitate to try a 175 ecu, but my 150 Supermag plugs come out paper bag colored. Idk if it would have enough fuel running a 200? I remember someone (probably Bobby v) saying he rode mismatched ecu's, and liked the 150 ecu. If I remember right he said "might surprise you". I'm thinking it might,.. when it blows up, or when it runs 5mph faster.



we jus saw such a difference with even tha right (same number) ecu's... i don't think its any particular ecu its because i don't think their R&D (mostly done by tha consumer), QC is/was good enough...ie: tha lean spot 17 for one example... seems ta me they had a hard time duplicating a particular curve over and over with their way of production... thats probably jus tha pessimist in me though.......

one more example.. bobby's original 225 ('94) promax with tha analog would turn well inta tha 7's.. others (ana or dig) might/maybe make inta high 6's.... all on same, same rig..... go figure

[killerpirate]

The starboard coils power is routed through the ecu for injector timing. The port bank isn't. Maybe you drop a pair of injectors when you unhook a plug wire at starboard bank?? Possibly it doesn't register a pulse from the coil going to ground???


That sounds interesting. Could be. But it still is weird to me that it idles so well on 3 cylinders, even on the shore. I would expect at least that it drop some RPM. I guess i will be going to the ramp and test there.


What about the map sensor? Your symptoms sound similar to a few old threads read, where a map was bad. Older manual sez a vacuum can be applied to hose and it should create a lean condition altering engine operation,. If no change occurs map sensor is not functioning. Map can also be checked with a efi tester.

The MAP sensor is located INSIDE the ECU correct? It is connected with a small hose to the intake manifold?
That would mean that both MAPS in the ECU are faulty (could be)

[LakeFever]

I too was confused by pulling plug wires on my first one of these. Some wires you pull and it’s as if it’s not doing anything. Pull another and it almost dies. I verified spark on all holes and tested it as suggested and it flew so I stopped checking things this way. I also didn’t know the ecu referenced the spark at all so that would make sense if pulling plug wires takes out injector pulses too. Probably why it does what I just described.

As for the ecu swaps iirc the A17 was the replacement for the first ecu that had the lean issue. I thought this was corrected with the A17 no?

[OnPad]

The MAP sensor is located INSIDE the ECU correct? It is connected with a small hose to the intake manifold?
That would mean that both MAPS in the ECU are faulty (could be)

Yeah, map is inside the ecu.

You make it out testing today?

Beautiful sunrise while fishing this morning!!
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