Mercury 3 liter 225 carb vs 250 efi block... pageing chaz and other 3.0 guys.

[RSWORDS]

Here is the situation. With the new family boat being sans motor the 225 carb motor for the hydrostream project is going to be volunteered for use till its 250 can be rebuilt.

In my research it seems that the 225 has exhaust reliefs, and the 250 doesn't. I see plenty of information saying the 225 efi and 250 efi share the same block ,(port timing and what not) but does the 225 carb block share the specs?

Will it be worth my time to swap all the 250 fuel system and electronics over to my 225 carb motor motor? Will it run as hard as the 250?

[Chaz]

Robert ,
We are obviously talking about early model twin computer , V-belt alternator era motors … correct ?

Then yes , even the 300 pm share the exact same block .

[RSWORDS]

Robert ,
We are obviously talking about early model twin computer , V-belt alternator era motors … correct ?

Then yes , even the 300 pm share the exact same block .

Yes sir we are. I knew all the EFI models had the same block but couldn't find anything on the 225 carb model.

Reckon I'll swap everything to get the new boat going and rebuild the other block this winter.

Any idea on factory ho on the 250s? I know alot of people say the 225 efi is 245ish.

[Chaz]

I had to go read your other thread to see what kind of boat you got ...
Vnemous pretty much threw the ball over the plate when it comes to making those motors run . You can only get so much before you have to start altering the port timing and upping the compression .
245 from a 2 shutter intake and all the rest stock .. I don't know , that's too far south of my test wheel .

[RSWORDS]

I had to go read your other thread to see what kind of boat you got ...
Vnemous pretty much threw the ball over the plate when it comes to making those motors run . You can only get so much before you have to start altering the port timing and upping the compression .
245 from a 2 shutter intake and all the rest stock .. I don't know , that's too far south of my test wheel .

I'll probably end up with a 300 ign at some point. Not gonna get too crazy with it though.

Yeah the new boat is something lol. Running 43 with a 225 honda I'd like to see high 40s with the 250efi

[bigshrimpin]

Here is the situation. With the new family boat being sans motor the 225 carb motor for the hydrostream project is going to be volunteered for use till its 250 can be rebuilt.

In my research it seems that the 225 has exhaust reliefs, and the 250 doesn't. I see plenty of information saying the 225 efi and 250 efi share the same block ,(port timing and what not) but does the 225 carb block share the specs?

Will it be worth my time to swap all the 250 fuel system and electronics over to my 225 carb motor motor? Will it run as hard as the 250?

95 - 98 blocks have exhaust reliefs in both 225 and 250
99 - 05 don't have exhaust reliefs in either the 225 or 250

[Chaz]

95 - 98 blocks have exhaust reliefs in both 225 and 250
99 - 05 don't have exhaust reliefs in either the 225 or 250

Early sq box V-belt first born till 2001
Late Motorola serpentine 2002 till death

I think the 250 xb was the only early model without notch's .