1993 Mercury 2.5 xri 175 hp oil injection system

[Crappiecrazy]

i just purchased a 1993 Skeeter bass boat with a 2.5 xri 175 hp Merc. it has been sitting up for 2 years and I'll be changing the impeller, fuel/water separating filter, thermostats, rebuild fuel pump, gear oil, etc.before starting the engine. i did not start it when i purchased it but did do a compression check on the cylinders. all 6 were at 120 psi.
i want to dismantle the oil injection system and go premix before firing up the motor. i have read lots of the threads posted here and feel i can remove the system from the motor. However, i am concerned about removing the detonation sensor and module that it is attached to.

if removed, will this effect the timing in some way ?
Also, the threads on this subject call for removing the rotation sensor near the oil injection pump. would it be ok to simply leave the rotation sensor and the detonation sensor in place and just remove the oil injection components?

i have the kit to plug the hole where the pump is and another plug for the starboard side of the engine.

any help will be appreciated.

[nitro_rat]

https://www.screamandfly.com/showthr...tion%20removal

[Crappiecrazy]

https://www.screamandfly.com/showthr...tion%20removal

that's the thread that shows the removal of the system, which is great and very detailed and simple. my engine is exactly like the one in those photos. i just don't know if removing the detonation components will mess up the timing. I'm needing to know if the detonation module and sensor, and rotation sensor can simply be left in tact. why is there a need to remove them?

[nitro_rat]

The idea is that when any of the timing modules fails it can effect the total advance and if you’re running on the edge for max performance this can cost you a motor. So you pull off all the modules and set your max total timing where you want it and then you can sleep well at night knowing that these black boxes aren’t going to cook your powerhead.

It would probably be a good idea to check the timing after ditching the modules.

Remove all plugs , attach a coil tester or ground out all plugs against the block so that when the motor is turning over the coils can expell thier energy. ( failure to do this can weaken the coils and smoke the switch boxes.) Attach a timing light to # 1 plug (On a V-6 Mercury # 1 is top plug on the right side looking at the rear of the engine ). Establish that your static pointer and O or TDC is accuratey aligned and on the nut accurate my opinion the ONLY way to dead nuts on this is to use a dial indicator!( Do this with a JSRE TDC dial indicator tool , hint hint ! ) once this is established open the foot throttle wide open and with the electric fuel pump ( if so equipted ) is either disconnected or enabled. Turn over with a hot battery over and over while aiming the connected timing light at the two correspondening points ( the static pointer and the rotating flywheel that has the timing marks on it ) as the timing light gets the signal from the firing # 1 plug it will flash and show where # 1 plug is firing in degrees. Adjust accordingly to the desired timing, I set all V-6 Mercurys that CAN be manually set and is not electronicly controlled at 25 degrees. You NO NOT NEED to start an outboard engine to correctly set timing ! I set TONS of them on my engine stand never had a problem in fact I've NEVER in 14 years of racing and building engines have EVER set one running .. ( Too dangerious , what a hassel , who the hell owns a "test" wheel and also I might get wet ! LOL........)

Merry CHRISTmas,

Hope that helps,

This iz politikly incorrect, and very unprofessional, but it'z way tha hell cheeper than $80........U kan also use it to check ignition fire...gap tha plugs az wide az ya kan, and it will sho U a week coil or problem...

6 used plugs, a foot ov 1 1/2 X 1 1/2 aluminium angle, drill 6 holes and tap to screw in tha plugs, and WHALA....U saved yaself $80 and earned tha rite to be called a cheepo, junkyard dog like ME!!!

[Crappiecrazy]

Thanks for that info. I’m going to be using the boat mostly for fishing. I don’t really have the need to be running high rpms for long durations. In that scenario, could I go ahead and leave the oil pump rotation sensor and the detonation module and sensor in tact after removing the oil injection pump and components ?

[Fishinmymission]

Rotation sensor serves no purpose anymore once you put in the plug. It senses through the aluminum block and doesn't seal anything so it can be removed to reduce clutter and weight on the engine or it can be left on the engine.
never had the knock sensor so can't help you there.

[Crappiecrazy]

Thank you for the info !

[nitro_rat]

If you ditch the oil injection you need to ditch the rotation sensor. Otherwise it will alarm as the pump won’t be turning anymore.

From my understanding of the detonation module function it advances the base timing 6 degrees once past 2500-3500 rpms. This it the range it can then retard timing if it senses detonation.

The idle stabilizer also advances the base timing, then pulls some out once you pass a certain rpm.

As these modules are capable of advancing the base timing they are usually ditched in a hipo application to prevent them from advancing the timing at the wrong time and cooking a motor. Since they both advance the timing, the base timing for a motor equipped with the modules will be less than a motor that’s not. After you yank the modules you should reset your timing to whatever you want it to be (usually around 25*).

1) The idle stabilizer adjusts timing at idle to smooth it out.
2) Between 5000 and 5600 rpm, it advances timing 6 degrees beyond WOT timing setpoint.
3) Beyond 5600 rpm, it drops the timing advance back to act as a rev limiter.
4) to remove it, I need to unplug the two wires that connect it to the switch boxes and set WOT timing advance to 25 degrees.

From Mercury manual : The Detonation Control System consists of a detonation
control sensor located on the port side cylinder
head and a detonation control module mounted on
the engine. The detonation control module has seven
wires:
• WHITE/BLUE - Connects to knock sensor, transmits
knock signal to control module.
• GREEN - Connects to #2 primary wire. The primary
voltage signals the controller to monitor
combustion “noise” during a window of time (See
Detonation System Function following).
• WHITE/BLACK - Two of these wires connect to
the switch boxes bias circuit terminals. A third
wire is spliced in one bias circuit (inner switchbox)
and connects to the idle stabilizer module. (See
complete Engine Wiring Diagram - refer to Section
2D).
• GRAY/WHITE - Connects to the ECM; signals
ECM to enrich fuel mixture when knocking occurs.
• PURPLE -
12 Volt power supply
DETONATION CONTROL SYSTEM FUNCTION
1. Combustion noise (or vibration) excites the piezoelectric
circuit located inside the detonation
sensor, which transmits a voltage to the control
module.
2. When cylinder number two ignition primary fires,
it signals the controller to look at a one millisecond
window of sensor output, which it retains as
a reference level of combustion “background
noise.”
3. When “background noise” reaches a measurable
value, usually between 2500 and 3500 RPM (it is
dependent on load), the ignition timing is advanced
6 degrees beyond what the mechanical
timing is set at. Timing advance is accomplished
by lowering the bias voltage.
4. The controller continues to monitor sensor output.
If the output exceeds a pre-determined
threshold level over the “background noise”
(which is indicative knock is occurring) ignition
timing is retarded by up to 8 degrees and fuel flow
is enriched by up to 15% until the sensor output
is reduced below the threshold level.
The detonation control system actually acts as an ignition
advance module, when knock occurs it takes
away the advance. Ignition timing will not advance if:
a. Knock sensor fails.
b. Blue/White wire becomes disconnected.
c. Black wire has poor ground connection.
d. Purple power wire becomes disconnected.

https://www.screamandfly.com/showthr...76#post3032476

[Fishinmymission]

He can leave the sensor in and keep it connected to the warning module or disconnect it. It makes no difference. He will have to disconnect the warning module from the alarm horn. If the rotation sensor is missing or not getting the correct rotation pulses timed to the ignition, the warning module will send an a rapid beep oil injection alarm.

[Crappiecrazy]

thanks for the wiring info and your input.i would like to keep as much in tact as possible regarding the misc. sensors and modules. I'm thinking of leaving the rotation sensor on the motor and just kill the alarm. i would also like to keep the detonation sensor and detonation module intact and letting it work as intended by Mercury to control the timing functions. what do you think about that ? will that work ? thanks !

[Crappiecrazy]

thanks for the reply! that makes sense. do you know the location of the warning module so i can disconnect it from the alarm horn? i'm guessing its under the dash somewhere?

[Crappiecrazy]

I wanted to thank all of you who replied to my threads about removing the oil injection system from my engine. got it done with everyone's input.

I wanted to share my story of how i discovered Scream and Fly. Before purchasing the Skeeter with the 1993 2.5 175hp mercury, which was the 3rd boat that i was looking at to buy, I ran across a beautiful 1991 19.5ft. Charger VF 195 bass boat with a 2.4 240hp Bridgeport Merc. This boat was a one owner, all original, in pristine condition and always kept inside. This boat was only used for fishing local lakes and not used more than 3-4 times per year. While doing research on the Bridgeport, I found the Scream and Fly Forum. I test drove this boat and now know why the forum is called Scream and Fly. This boat did exactly that. It was extremely fast and extremely load. I wanted this boat real bad but i ended up passing on it. It was really too fast and too loud to be able to take my kids and wife fishing and/or tubing at the lake. I guess i can say that i got to experience screaming and flying once in my life.

Thanks again to all !!