mercury 175 efi issues acting up rough idle cuting out then runs great

[RHowe]

I have a 1996 mercury EFI new block is 1 year old.

My Engine will run perfect then when I re start it on occasion it will idle reel poorly likes its fouled.

If I go to WOT the boat will BOG , I will then idle put in nuetral rev it and it will clear out ,fix itself.

Then it runs great for 3 hours stop go ect.


It will then repaet itself all over again.


Here is what has been done so far.


new anti syphon valve


new primer bulb


new fuel filter


new spark plugs


Cleaned out VST and re installed.


Yet the issue is still there.



What is my next thing to do?

[Highcentered]

It's gonna get posted anyway by someone whether it's your problem or not so I'll take the liberty of being the first. Not all fuel system components are created equal so it really is good to have the best there is with the liquid they try to pass off as fuel these days. Definaly run ethanol free gas if you can find it.
http://www.bbcboards.net/mercury-3-l...tem-first.html
Anyway, have you tried running some Seafoam through it? You can also get your injectors professionally cleaned by Don Weed who will be by shortly to try to help you. If it runs fine after clearing it out it's obviously fuel related somehow whether it be bad gas, poor quality oil, injectors dirty, etc. A lot of people keep Seafoam in their tank to keep fuel and carbon related performance issues from happening. If I don't run my '94 efi wot enough it gets cranky. It runs its best when I'm fishing the river a lot because the run back to the ramp is usually several miles with the hotfoot pegged. ALWAYS idles smoother at the end of a long run.

[EuropeanAM]

Welcome to BBC!

Recommendations (in this order):

-Ensure that ALL recommended items in the following post have been addressed (OEM components, and AT THE SAME TIME): http://www.bbcboards.net/mercury-3-l...tem-first.html

-Check fuel pressure AT IDLE, under acceleration, and then 15, 30, 60 seconds after key turned off. Report back with results.

-Have injectors been cleaned/serviced/calibrated as needed???

[Chickfisher69]

sounds like a bad ecu cutting out 2 injectors. these 824003 ecu's are known for this problem . Do all the cks listed than either swap ecus or send to simons motor sports or buy a new one. just had one repaired by simons and it works great.

[RHowe]

Ok i looked around at my motor and found that the wiring hrness box on the starter solenoid was super loose nearly hanging there, my guess is this was shorting things out and causing issues, i fixed this ran the boat and the above issues went away, however now i ran say 25 miles no issues then at 35 mph my boat just cut out and shut off. i waited started right back up then shut off when getting on plane. Waited started right back back up no issues for 15 miles, then it did it again shut off while on plane.???

Like it just cust out. No change to the check systems beeps, no issues running the boat. Just cut out when on pad???

what should I look at next??

[EuropeanAM]

Check/monitor BATTERY VOLTAGE AT THE BATTERY with a DVOM (digital volts/Ohms meter) while the engine is running.

Record battery voltage WHEN (or if) the engine shuts down. Very important to know if the voltage has exceeded 14.6 VDC.

You also should visually inspect the VOLTAGE REGULATORS for signs of melting, burnt spots, etc. Check for melted/burnt/browned/blackened bullet connectors (especially the ones on the RED or YELLOW wires). If any of these are noted- replace BOTH regulators, and any damaged bullet connectors.

[RHowe]

Check/monitor BATTERY VOLTAGE AT THE BATTERY with a DVOM (digital volts/Ohms meter) while the engine is running.

Record battery voltage WHEN (or if) the engine shuts down. Very important to know if the voltage has exceeded 14.6 VDC.

You also should visually inspect the VOLTAGE REGULATORS for signs of melting, burnt spots, etc. Check for melted/burnt/browned/blackened bullet connectors (especially the ones on the RED or YELLOW wires). If any of these are noted- replace BOTH regulators, and any damaged bullet connectors.

is this the right part number to replace??
on the boat the number is different 882751??

828151A 1

RELAY ASSEMBLY

[RHowe]

No burnt wires can be found at this time.

[RHowe]

THE PART NUMBERS ON THE PARTS ARE 882751/SAEJ1171/ISO8846

IS THIS THE RIGHT REPLACEMENT PART NUMBER ??

828151A 1

RELAY ASSEMBLY

[EuropeanAM]

Check/monitor BATTERY VOLTAGE AT THE BATTERY with a DVOM (digital volts/Ohms meter) while the engine is running.

Record battery voltage WHEN (or if) the engine shuts down. Very important to know if the voltage has exceeded 14.6 VDC.

Don't forget to monitor the above....

[RHowe]

Ok found burnt wires on regulator. replaced regulators.

now battery ready 12-14 volts as its suppossed to.

But te problem still persists.

Bogging at idle and cutting in and out while getting on plane.

The boat is not shutting off now that voltage regs were replaced.

But is still intermitantly having rough idle and bogging when wot to get on plane.

What to check next?

Fuel pressue is good.

[EuropeanAM]

Ok i looked around at my motor and found that the wiring hrness box on the starter solenoid was super loose nearly hanging there, my guess is this was shorting things out and causing issues, i fixed this ran the boat and the above issues went away, however now i ran say 25 miles no issues then at 35 mph my boat just cut out and shut off. i waited started right back up then shut off when getting on plane. Waited started right back back up no issues for 15 miles, then it did it again shut off while on plane.???

Like it just cust out. No change to the check systems beeps, no issues running the boat. Just cut out when on pad???

what should I look at next??

Any chance you can provide a picture of what you were working with here?

Have you disconnected the cannon plug, CLEANED the pins, CAREFULLY spread the male pins SLIGHTLY, reconnected, and STRAPPED THE CONNECTOR IN PLACE?

Fuel pressue is good

What (exactly) is your fuel pressure, under each of the following conditions:

-Idle Speed
-Under Acceleration (when the engine is failing to accelerate)
-15 Seconds after Key Off
-30 Seconds after Key Off
-60 Seconds after Key Off?

[RHowe]

i have pulled the ECU plug apart, it was difficult to spread male pins,

what should I clean it with?

How do i check this fuel pressure?

My mechanic checked it when he tested the boat, it was a 1lb of pressure so he replaced the anit syphon valve.

Then it was at 4lbs as required according to him.

[EuropeanAM]

i have pulled the ECU plug apart, it was difficult to spread male pins,

what should I clean it with?

You are NOT supposed to be altering the pins on the ECU PLUG. Read above- it is the CANNON PLUG (ignition switch harness plug).

I would strongly recommend obtaining an OEM (Mercury) Repair Manual for your engine. It outlines and explains various tests and repair techniques.... including testing fuel pressure.

Will come in handy for your mechanic as well.

[calfisher71]

Ok, it was the cannon plug not the ecu plug.

I have taken to 3 mechanics now.

The last one went thru everything all over again.

He found some vacuum issues, re checked all fuel lines, the new primer bulb was bad from Mercury and caused the cutting out.

The cutting out is fixed now.

All fuel lines have been replaced.

Ran the boat again 2 days ran perfect, I thought the issue was finally fixed.

Then day 3 the bog was back????

My ecu has been checked and is fine.

This is so annoying the amount of money spent to fix and test and fix and test, yet no results.

Help!

[EuropeanAM]

Then day 3 the bog was back????

My ecu has been checked and is fine.

Can you explain precisely "how" the ECU was checked, and determined to be "fine"? Since your problem has proven to be intermittent... it's entirely possible that ANY testing that has been done was not uncovering the actual problem (especially if, due to the intermittent nature, it was not present AT THAT MOMENT).

If you had a NEW OEM Mercury primer bulb that was bad (purchased within 1 year)- it can be replaced free of charge by any authorized Mercury Dealer (under the Parts and Accessories Warranty).

You've been given several suggestions above, for which no specific testing results have been provided. It's very difficult to continue assisting/diagnosing when no results are available...