2004 mercury 250 efi removal of oil injection?

**camaroguy71** · 10-15-2018, 06:08 PM

Hey, thanks in advance for any help with this. I have a 2004 efi 250 motor that i want to run premix in instead of the injection. Question is i was told i cannot do it? Can i do it an d how do i? What is the process and the proper way so i have no alarms or issues?
Like i said i was told from the dealer that i cannot remove the oil injection and use premix?

**cali kid** · 10-16-2018, 08:03 AM

You can remove it. Just unplug the oil tank warning sensors, and block off the pressure hose to the big oil tank, you can also unplug the oil pump. The dealer must have thought you have an Opti.

**Chaz** · 10-16-2018, 08:04 AM

The easy way is to leave the pump on the side of the block. Make sure it's still full of oil and run a short 1/4" I.D. hose as a "loop line" from the inlet to the outlet barbs. Remove everything else.

You could remove the pump and put a resister in line. but if you hook it up bass-akwards, the wire breaks and it touches ground, not enough resistance, etc ... it could damage the ECM .

Personally ... I'd rather let the motor mix it's own oil . It's smarter than me , it's gotz more time to sipher on it than I do . They idle at something like 200 to 1 and go to 40 to 1 at WOT or something close to that. ( we had that seminar out of the manual a couple months ago .. LOL )

**Chaz** · 10-16-2018, 08:13 AM

Cali ,
I don't remember if the oil bag sensor is looking for an , open , closed , or scaled resistance , in that circuit . It's he11 getting old ..

Another one for the manual I recon ..

**hsbob** · 10-16-2018, 11:11 AM

if its a multi port oil injection like the optis, then you cannot remove the oil injection and use premix. eg the rod ends do not have oil catch holes in the fuel stream, etc.

**cali kid** · 10-16-2018, 01:49 PM

Originally Posted by hsbob

if its a multi port oil injection like the optis, then you cannot remove the oil injection and use premix. eg the rod ends do not have oil catch holes in the fuel stream, etc.

One line from the oil pump goes strait to the VST and mixed there, on the EFI version.

**cali kid** · 10-16-2018, 01:59 PM

Originally Posted by Chaz

Cali ,
I don't remember if the oil bag sensor is looking for an , open , closed , or scaled resistance , in that circuit . It's he11 getting old ..

Another one for the manual I recon ..

The last one I did, I just unhooked everything and it worked fine with no alarms, so the sensor must read, open, ok, closed, alarm. I did re-install the system later on, and agree with your last statement.

**RSWORDS** · 10-16-2018, 02:42 PM

The electric pumps are so trouble free why would you want to remove it a deal with mixing? As said the computer is smart enough to adjust the mixture as needed

**Silvershiner** · 10-16-2018, 07:49 PM

I am definitely no expert on these motors but I like the oil system instead of premix.. question for everybody .... Is there some fairly cheap preventive maintenance that a person can do to prevent failure???

**Chaz** · 10-18-2018, 09:23 AM

Originally Posted by hsbob

if its a multi port oil injection like the optis, then you cannot remove the oil injection and use premix. eg the rod ends do not have oil catch holes in the fuel stream, etc.

This is true. It's also pretty amazing that they chose to inject the oil just below the second ring @ an angle towards that scalloped out area by the wrist pin. Obviously, its maze shape in the scallop provides the timing of the oil cycle. The rest of the time this oil hole is blocked by the full length skirt.

I am definitely no expert on these motors but I like the oil system instead of premix.. question for everybody .... Is there some fairly cheap preventive maintenance that a person can do to prevent failure???

Make sure there's oil in the tank ....

Just check your hose's and connections. (nothings falling off) Just snug the caps , no need in over tightning them and cracking them. The system will lose pressure . The parts are made of plastic, take care of them and thay will take care of you ..

**Silvershiner** · 10-18-2018, 09:44 AM

Well said Chaz... had my oil cap crack on motor Reservoir recently luckily I was paying attention to my motor and noticed it right away except I still had a mess underneath the hood... have heard that a guy should replace a check valve somewhere on the motor every once in a while as in years that can prevent problems???? What is everybody's opinion on that...

**vnemous** · 10-18-2018, 10:19 AM

There is a check valve on starboard side of block that does go bad. It pressurizes the oil tank in the boat which pushes oil up to tank on engine. I would at least suggest keeping a spare check valve on the boat. They do go bad. Follow the oil line from boat oil tank back to engine block behind the starter. Part #8781051 20 bucks well spent JMO