Trying to identify my Mercury

[rhafley]

I recently bought a 1991 Champ with a 1991 Mercury V6. The stickers on the cowl say it's an XR4 150 but it looks like a 2.5 block and has horizontal reeds. The serial number is 0D007895.

I'm trying to:
#1 properly identify this engine (because who knows what happened in the last 26 years) and find out for sure if I can use the serial number to buy parts.
#2 Find out if the engine is reliable and what problems I need to watch out for.
#3 Find out what, if anything, can be done to pep it up

It runs great, pushes my boat to 63 mph. Compression tested 130 psi cylinder pressure across the board +/- one or two psi. i looked in the cylinder with a camera and can see that it has thick steel or cast iron sleeves and some kind of relief slot in the top of the exhaust port. Thanks for your help.

[JOE54]

that ser num does show to be 2.4 xr4 born 1990,see if plug on top back of block matches, most problems were related to voltage reg and small gear case[upper drive shaft bearing],cyl head work,reed replacement,advance module removal ,larger diameter gear case 1.87 ratio will help ,boat set up,good prop,Tempest be my choice,it looks like 2.5 casting but has 2.4 sleeves. they even made some 135 same block 2.0 sleeves,xr6 is 2.5L,agian see if plug on block ser num matches od007895, hope this helps ya JOE

[skeeter91]

did the 2.4/2.0 motors come with idle reliefs? i was told the 150/175 2.5 efi motors were the 2.5's with them, but 89-91 was a mixed part run for Merc. too!

[rhafley]

,agian see if plug on block ser num matches od007895, hope this helps ya JOE

Is this plug under the flywheel Joe?

[myron]

to my knowledge the 2.4 never had any idle reliefs

[JOE54]

plug should be just behind flywheel port side top of block look close may been painted/ or pull cyl head measure bore/ bore scope look at intake ports 2.4 should have finger ports in cyl

[cajunrgfm]

it is a 2.4 "fat block",

[rhafley]

So since my 2.4 is essentially a 2.5 on the outside then is is safe to say if I could wrangle up a 175 or 200 longblock my externals will bolt on and operate?

[EuropeanAM]

While they may bolt on, the carbs and the exhaust tuner would be the biggest problem areas.

Is there something wrong with this one, as it is?

[rhafley]

Is there something wrong with this one, as it is?

No sir, it runs great. I'd like about 3-5 more mph out of the boat.