Mercury 225hp 3.0L....

[tony1204au]

Does anyone know the differences between a 225hp and a 250hp 3.0L Merc...
Its a 2003 with the motorola ecu on the side.
Looking at the parts book, the heads look the same.
Could this possibly be just a different ECU??? or is the porting different??

[XstreamVking]

Biggest diff I know is the 250 has a 4 hole intake, 225 has 2 holes. Diff computer, also...

[tony1204au]

Thanks for the reply... That is the case with the earlier ones up till 2001 I think...
This one is the later type with the downdraft single hole intake... Very similar to an opti setup, but just an EFI...

[XstreamVking]

I should have read your post better... (its 6 am and no coffee yet) You said it was an 03, for some reason I was thinking older. There are some mods to get more hp from a 250. They have been posted here. Might be able to find em.... Seems that a pr of 300 heads and 300 electronics was the biggest diff to make 300 from a 250.

[mrcrsr]

change the ecu

[Go Time]

Porting in the blocks is different. 225 has exhaust port notches, 250 does not.

[mrcrsr]

Porting in the blocks is different. 225 has exhaust port notches, 250 does not. not true, that had to do w/ the years the engines were built, 3 litres(all) had port notches up to about late 99, then they got rid of them

[Stitch King]

Checkmate250 made a 3.0 liter with the Motorola 555 ECU outperform a 300xs using a Simon tune and lots of Simon parts.

I believe it was lightened flywheel, tighter heads, intake, poppet diverter, and the ECU tune.

I was on the boat and the motor was very strong and responsive. It was so good that we outran another Checkmate 21 with a 300xs owned by his buddy and we had 3 more people in the boat than the other guy.

[Stitch King]

The only other 3.0 liter (including 300x) that had such instant throttle response was my old motor with a Wolf V500 ECU running the show. Talk to Charlie (Mrcrsr) above about that. :)

[kct11]

Checkmate250 made a 3.0 liter with the Motorola 555 ECU outperform a 300xs using a Simon tune and lots of Simon parts.

I believe it was lightened flywheel, tighter heads, intake, poppet diverter, and the ECU tune.

I was on the boat and the motor was very strong and responsive. It was so good that we outran another Checkmate 21 with a 300xs owned by his buddy and we had 3 more people in the boat than the other guy.

I woulnt go so much by that, I couldnt drive it then...:D Joe's boat does run real good though.

[tony1204au]

Its sounds like this 3.0 has a bit of potential... A 300xs would of been nice, but the budget doesnt allow for it unfortunately...
Does anyone know about the porting.... I want to put this powerhead together, but Im holding out to see if I should get it ported first...
I just dont want to be porting, unless I know of a port map that will work...

[XstreamVking]

http://www.biggerhammer.net/mercury/ This site has some good info for the 3.0 and 2.5 and 2.4. 3.0 stuff is at the very end...

[mrcrsr]

port timing is the same between the older style(pre 2000 2 computer engines) including the 225,250 and 300 promax, some used different cyl heads for higher compression, all used different computer tuning and any 250/300 used a 4 butterfly intake system. as far as the newer motorola stuff, 225/250 share the same port timing, computer tuning and possibly the heads are different, the 300x has different port timing. i run a wolf ecu w/ basically my own software and have been happy w/ the results, i'm also running alot higher compression w/ quite a bit of other stuff done to the block and port timing mods

[tony1204au]

Some great info there.... Thanks....
I guess what i really want to do, is upgrade this 3.0L to factory specs of one with more power... Keep in mind we are dealing with a motorola type engine...
I know that the heads are the same for the 225 and 250 in '03, and if you say port timing is the same, then the ECU is the extra 25 ponies..
Give me an inch and I want a mile....lol...
Can I port this thing to 300x or 300 PM specs, get the right heads and ECU flashed and be around the 300hp mark?? Or is there more to it..

[Stitch King]

Unless you are going for the absolute max power you can squeeze out, I would not mess with the port timing. That mota can make plenty of power as is with just bolt ons. I've even heard of guys dropping the 300 XS stroker crank in the 225/250 block. Keep in mind that there needs to be work done to avoid the pistons meeting with the heads.

FWIW, making big power at lower rpm's translates to longevity. These motors make max power in the low 6000 rpm range and can crank 1.62 gears and 32+ pitch props easily. Porting will move the rpm band up and yes higher rpm with a given amount of torque means higher horsepower (based on the formula) but higher rpms shorten the lifespan unless some real precision machining work is done.

Call Simon...

[Stitch King]

I woulnt go so much by that, I couldnt drive it then...:D Joe's boat does run real good though.

Did you guys ever run again head to head after he got it dialed in?

[mrcrsr]

Unless you are going for the absolute max power you can squeeze out, I would not mess with the port timing. That mota can make plenty of power as is with just bolt ons. I've even heard of guys dropping the 300 XS stroker crank in the 225/250 block. Keep in mind that there needs to be work done to avoid the pistons meeting with the heads.

FWIW, making big power at lower rpm's translates to longevity. These motors make max power in the low 6000 rpm range and can crank 1.62 gears and 32+ pitch props easily. Porting will move the rpm band up and yes higher rpm with a given amount of torque means higher horsepower (based on the formula) but higher rpms shorten the lifespan unless some real precision machining work is done.

Call Simon... ken, i actually went a little further then the 300x port map in my 3 litre, i have the limiter in the wolf set to 7k rpm, last time out w/ the new skater it was rite there, i actually have 275 hrs on this engine, and it hasn't led an easy life, including running almost 50 gals of fuel thru it on a dyno to set up the fuel curve, but you definetely have to know what you're doing to modify port timing. i did lose a bit of lo end torque from doing it, even running 160 psi compression i never got it back. as far as the 3.2 crank, you don't even gain 200 cc's from it

[HighVelocity]

I asked the same question 4 years ago and nobody really knew the difference then either... Lots of good guesses but no one could say for sure... I'm thinking maybe Eric Simon knows if anyone...

[Stitch King]

ken, i actually went a little further then the 300x port map in my 3 litre, i have the limiter in the wolf set to 7k rpm, last time out w/ the new skater it was rite there.

Sounds sweet!!!! Does the ride you offered me when the motor was on your old boat transfer? What kind of speeds are you seeing?

[mrcrsr]

we were still setting the skater up, it went 96 using a friend's 1.75 sportmaster, he borrowed my 1.62 sporty to try on his boat,i'm figuring the 1.62 will be perfect for this setup, i currently have the boat apart for paint, but your more then welcome to come for a ride when its done. the next 3 litre i build will be crankcase injected, the beauty of running the wolf, no limitations!

[Stitch King]

It's going to be a few months before I'm down there but you are on the list to visit.

Yes, the 1.62 gears will make a difference. IIRC, the step down from 1.75 was sort of like adding 2" of pitch to a prop on my old Liberator which translated to a 500 rpm drop.