help ID 2.5 FrankenMerc

[Varmint]

can't find a serial number,but has 225/260 C3 heads with dowel pins,steel bore,(put a magnet to bore and pulled it out of my hand),has been converted to carb,with WH22's,has a small hole in front half,looks like it spit a piston ring,makes sense to call it a promax,except for the fact the block appears to have a date code stamp of 03 08 90.? haven't had time to tear it down further,but has 3.5" bore also.

[Varmint]

[Varmint]

a weld on each cylinder

[Varmint]

[Varmint]

pretty sure it's a promax frt. 1/2,has an oil injection port,with a block off plate,whereas the 245/260 was just a machined boss,and has 7 petal reeds,

[90 5.0]

That's some serious frankin' mercin' going on I think?
wasnt 91 first year for 2.5?

[Varmint]

yes,was no promax yet,so,don't know what it is,

[90 5.0]

My first guess would have been 200 promax with a 2.4 flywheel on it but the date is throwing that off.

I have no idea

[Varmint]

My first guess would have been 200 promax with a 2.4 flywheel on it but the date is throwing that off.

I have no idea

all I know is it hit 90 on an xtb21 before it popped something thru the frt. 1/2

[Krazymaan]

The three welded up holes on the sides of the cylinders would have been where the rubber bleed off tubes went.

[wrechin2]

That's some serious frankin' mercin' going on I think?
wasnt 91 first year for 2.5?

91 was the first "fishing" 2.5 if you will. I had one in the shop with 2-XX-90 date code and was black. This one has had the bleeders welded up and probably bead blasted to mimic being anodized. just my .02

[Krazymaan]

never seen a "single number" year stamp?

Try looking this number up in the Merc books. Its a single digit. It will get you nowhere, buy yet it exists. LOL

[tlwjkw]

not very often but date stamps have been wrong... ask Bobby!...... 1st gen block with fat block build date!.. once stamped, no goin' back.. can't be surprised with anything merc builds at anytime!

[Krazymaan]

a weld on each cylinder

What are the three drilled and tapped bosses for on the side and what is the big boss facing upwards for. Every photo i ever see, nothing is ever attached to them. Is that a 2.5 thing or can 2.4's have them too? I've seen 2.4's for sale with those but none of my 2.4's have any of those drilled bosses/pegs/posts, whatever you call them.

[tlwjkw]

they are for additional boxes that are use on various motors.. ie: idle stab., oiler, knock sensor etc. early (analog) efi hot rods for tpi..... jus a lotta different things... yours was way before all that stuff came out.....
jus take a look at bone stock power heads and you'll see.............