Help with an Mercury 150 2.5 Carbed to EFI 175 conversion

**Gsmith223** · 12-28-2016, 10:43 AM

So long story short I blew a powerhead on my 1998 Merc XRI 150. I traded it in on a rebuilt XR6 150 but soon started having issues with it. The guy I bought it from offered to swap me back my original motor the 98 XRI but he had removed the EFI parts and put on carbs. So I went ahead and did it. So the motor I currently have is a 1998 XRI 150 serial number 0D275859 with carbs from a mid 90's XR6 and NO oil injection. I am not happy with the power from this current setup 52 MPH at 5500 RPMs, same motor before I blew it was hitting 60 MPH at 5800 RPMs the XR6 was even better hitting 62mph at 6000 RPMs. Everything has stayed the same lower unit, prop motor height all the same yet the rebuild with carbs just doenst have the power.
The guy I bought the rebuild from said it might be do to the carbs not matching the block and heads right. They are model WHM 14a
So in my quest to get my speed back I came across a buddy who blew is his 1998 merc 175 EFI motor that will sell it to me at $600, I need a lower unit any how so I thought this might be a good opportunity to get my power back.
I am considering trying to convert my motor back to EFI buy using his motor as a donor but realize his motor blew for a reason so I dont know if this is all worth it and how hard the work would be? I would like to add the oil injection back too but not sure how much of his oil injection I can use or have tested to make sure its good before I go this route. I can send the injectors off for testing\cleaning but I am not sure how much trouble this is going to be? I dont expect to get 175 HP but just get back to where I was before would be great.

My other option is to try another set of carbs to see if that improves my power.

Any help or options will be greatly appreciated

**CircleHook** · 12-28-2016, 12:58 PM

$600 is very good price- buy it just for parts
I do not think 14s or the right carbs- pretty sure they should be 16s

others will chime in....

**skeeter91** · 12-29-2016, 09:15 AM

ID SNAP THAT MOTOR UP!you can make your $ back or at the least,break even.convert it back to EFI and live happily ever after!send the injectors and ecu to Brucato fuel injection,they will scan the box for any issues and flow the injectors before and after cleaning,they are good people to deal with.and last of all,id stay away from the guy that screwed you on that motor deal!

**Gsmith223** · 12-29-2016, 09:37 AM

Originally Posted by skeeter91

ID SNAP THAT MOTOR UP!you can make your $ back or at the least,break even.convert it back to EFI and live happily ever after!send the injectors and ecu to Brucato fuel injection,they will scan the box for any issues and flow the injectors before and after cleaning,they are good people to deal with.and last of all,id stay away from the guy that screwed you on that motor deal!

So the conversion back is possible but how much work is it going to be is my question? is there a way to verify his oil injection system still works? Should I just premix with the EFI installed?

**skeeter91** · 12-29-2016, 09:42 AM

id premix,but you can keep the oil injection as long as the crank gear is good and you have all the parts.the conversion is not a big deal so long as you have ALL the correct sensors and ohm the out , per mercury service manual spec.
if you dont have a service manual,get one!

**Dave Strong** · 12-29-2016, 12:26 PM

Go with the EFI, but don't use the oil injection. JMO

Dave

**rock** · 12-29-2016, 06:57 PM

You really need to lose that oil injection. It's a bad thing.

Rock

**Dave Strong** · 12-29-2016, 07:15 PM

Originally Posted by rock

You really need to lose that oil injection. It's a bad thing.

Rock

If that motor ever got warm the plastic gear will fail sooner than later.

Dave

**Gsmith223** · 01-03-2017, 03:44 PM

Okay so looks like I would get rid of the oil injection but will the 175 EFI work on the 150 block I have been told there are some difference with porting between the two and the 175 ECU will be too rich for the 150?

**skeeter91** · 01-03-2017, 04:15 PM

its my understanding that the 150 and 175 EFI are ported the same,ecu is different?those in the know will answer this for sure!I do know of some that have put 150 ecu's on modded motors and they scream?!

**CircleHook** · 01-03-2017, 04:49 PM

Originally Posted by skeeter91

its my understanding that the 150 and 175 EFI are ported the same,ecu is different?those in the know will answer this for sure!I do know of some that have put 150 ecu's on modded motors and they scream?!

this would be a good question for James Perry

**90 5.0** · 01-03-2017, 05:04 PM

Originally Posted by Gsmith223

Okay so looks like I would get rid of the oil injection but will the 175 EFI work on the 150 block I have been told there are some difference with porting between the two and the 175 ECU will be too rich for the 150?

That is correct

**tlwjkw** · 01-04-2017, 08:27 AM

Originally Posted by Gsmith223

the 175 ECU will be too rich for the 150?

jus theory ....

you will never know 'bout tha ecu deal till ya run it.. they all vary on what will run on what.. don't think any two "production" ecu's run tha same!............. jmo

**FORBESAUTO** · 01-04-2017, 09:50 AM

Rich ain't never hurt nobody. Try it and see, if too rich just hunt ya down another ecu. Very possible could run just fine.

**skeeter91** · 01-04-2017, 09:59 AM

if it runs really rich,which i doubt it would,you can lean it by 10% by connecting the leads from the temp. sensor in the plenum.i did this with a 200 ECU on a 175 to confirm the 175 ECU was bad and it worked fine,but was a little sluggish on holeshot,but not by much.