2003 Mercury 2.5 xr6 porting

**Kdybalski** · 05-30-2021, 11:38 AM

I have a 2003 2.5 150 xr6 that I want to get extra performance out of and thinking about changing the port timing while the block is apart and putting a better timer on it while I am in there. It has super low hours, but had a problem with one piston, thus the tear down. This motor does have the compression relief built into the cylinder. Some say no go on any mods, but others say it does not make much difference and will respond to port work? Any suggestions!! Btw, motor is going on a somewhat light bass boat and want to get over 200 hp to push lager prop. Some say the motor stock is around 168 to 170 hp now. It has the bigger carbs on it now. Any other mods suggested. If you say tuner, which one. What’s best bang for buck.

**tlwjkw** · 05-31-2021, 01:42 AM

first off.. its a "cdm 'lectronic" motor.. no mater what ya do to it with that type of 'lectrics its limited to what they will support.... ya want more stuff ya need something ya have more control over (switch box 'lectrics).... jmo.

**Kdybalski** · 05-31-2021, 08:59 AM

Originally Posted by tlwjkw

first off.. its a "cdm 'lectronic" motor.. no mater what ya do to it with that type of 'lectrics its limited to what they will support.... ya want more stuff ya need something ya have more control over (switch box 'lectrics).... jmo.

Not sure what options I have as I am not very familiar with this electronic setup. Not sure if you can remove the rev limit box or what. I think it has a timing adjustment as well built into the box. Not sure best route to make it run.

**tlwjkw** · 05-31-2021, 09:10 AM

switch box 'lectrics only way.

no changin' any of tha cdm/'lectronics perimeters on production motors.. stuck with what it is.

**Chaz** · 05-31-2021, 01:50 PM

While it's apart is the perfect time to spice it up a little. You will find casting flash that can be removed , sharp corners that can become more 'air friendly" and mismatched sleeve to block area's that can be brought into line .

The exhaust port notch makes them idle a little better and keeps them from detonating under slow speed high throttle position conditions. (high load) Most don't like them, me included. But if that's what you have .. then go with it .. above 4-5000 rpm it is said .. you , me and the motor won't even know that they are even there ..

You will need to have the heads milled to bring back the compression lost from raising the exhaust port .. Both places a little is better than a lot ..

As long as you don't move the port timing too much , your ignition box will work fine, be more reliable and cleaner looking.
Using a remote fuel pressure regulator you will be able to adjust the A/F ratio, globally.

Chris Carson sell's reeds for blocks that have had the rubber removed . Removing the rubber creates a larger window and the reeds tend to seal up better on the newly honed (wax on - wax off)

flattened surface. (he offers block prep as well)

A EGT meter will help you arrive at a tune-up without hurting it again ...

**David** · 05-31-2021, 07:17 PM

Is the XR6 like the XR4? 'Everyone' recommended a tuner change and removing the idle stabilizer module on my old XR4. It did respond to more spark advance with a couple of MPH. Of course the XR6 is a 2.5L but do the tricks carry over?

**tlwjkw** · 05-31-2021, 11:07 PM

pre 2000 will.. tha production 2000 up uses o-ring block/heads.. most can't jus cut tha heads.. tha deck is also 'bout 40 thou taller.. some jus cut tha deck down and use pre o-ring heads/gaskets (check head bolt length)... responds well that way... but like said, tha main thing is tha production electronics.. they will let ya do jus so much and thats it.... if tha control module don't like it (not with in its perimeters) it won't let it happen.

**Chaz** · 06-01-2021, 08:38 AM

Originally Posted by tlwjkw

pre 2000 will.. tha production 2000 up uses o-ring block/heads.. most can't jus cut tha heads.. tha deck is also 'bout 40 thou taller.. some jus cut tha deck down and use pre o-ring heads/gaskets (check head bolt length)... responds well that way... but like said, tha main thing is tha production electronics.. they will let ya do jus so much and thats it.... if tha control module don't like it (not with in its perimeters) it won't let it happen.

He's not lookin to make 300+ Just a little more for his bass boat ..

O-ring heads .. pretty simple to do , and when they are done ... reliable sealing .

I have about 40 factory head gaskets .. in case you need some antique NOS parts.

**tlwjkw** · 06-01-2021, 08:50 AM

you gonna cut his heads for him at a price he can afford or willin' ta pay?.. no mater, tha production 'lectronics are gonna determine what it does anyway...

**Kdybalski** · 06-01-2021, 09:44 AM

Originally Posted by tlwjkw

you gonna cut his heads for him at a price he can afford or willin' ta pay?.. no mater, tha production 'lectronics are gonna determine what it does anyway...

Thanks guys for the responses. It has the airing heads. Not sure if changing the port configuration would help, but I’m game while the block is down. Any recommendations on port dimensions to work towards. In addition, which tuner would be best. I am going to order stuffers and reeds from Chris.

**tlwjkw** · 06-01-2021, 10:29 AM

someone on here should have tha measurements ya lookin' for?.. maybe they will see this and share... good luck with it.. hope it all turns out well..

**tlwjkw** · 06-01-2021, 10:37 AM

i did have this thread saved in case ya interested?... but don't think your stuff would make use of its full potential?

Mercury Port Heights vs APBA Ports heights (screamandfly.com)

**Chaz** · 06-02-2021, 08:54 AM

Originally Posted by tlwjkw

you gonna cut his heads for him at a price he can afford or willin' ta pay?.. no mater, tha production 'lectronics are gonna determine what it does anyway...

I didn't see where he said he was here to sign up for welfare .. or is dirt poor. I mentioned that if he was going to raise the exhaust port ... that he was going to need to clip the heads . I get it now , just because you don't have the capability to mill the heads, you think that no one else can ....

I don't advertise what I can do on here. I can barely keep up with what walks thru the door and my regular's as it is ...

You , him , anyone else would have to wait. I'm finishing up a set of 3.3 Yamaha heads , just like these. I assume .. you can't do these either ...

https://www.screamandfly.com/showthr...5-HPDI-rebuild

As far as the spark box .. well, lets not get into that online. The mothership thinks it's still owns it ..

Ahh .. so nice to see you can offer something semi-positive to a new guy ..

i did have this thread saved in case ya interested?... but don't think your stuff would make use of its full potential?

Mercury Port Heights vs APBA Ports heights (screamandfly.com)

**tlwjkw** · 06-02-2021, 08:58 AM

i'm waitin' on all tha pictures and magazine articles on tha head cuttin'???

**Chaz** · 06-02-2021, 06:20 PM

Magazine articles .. how bout the cover ..

Like JJ the boss says ... Off with ya whole head .. bouyy ..

I thought you didn't like my pictures ..

We gotz heads to weld up ..

We gotz billet heads ..

We gotz milled Brunswick heads ...

We gotz filled Brunswick heads ..

And you gotz a bad attitude ... but here's your chance ..

The late model stuff you don't understa .. err .. like.

Please tell us the fuel load in Lbs / Hr , BSFC @ stepped RPM , MS of injector off time and duty cycle .

And of course , the timing curve. Spark dwell , CDM charge time .

Take all the time you need ..