Mercury 25XS Serial numbers

[champhotrod]

Does anyone know what serial numbers were on the original 25XS engines in 1985??

Cooper Jess

[jp183w]

Cooper,

From the dealer site it shows the serial numbers starting at 85A001 in 1985. In 1989 the serial numbers started
at B290347.

Hope this helps, Jim

[champhotrod]

So what serial number would be 77H051 ????? 25SS I guess.

Cooper

[jp183w]

From everything I see on Mercnet the race engine serial numbers up till the late 80's were the year a letter and the three digit engine
serial number. The number you have would be a 1977 engine so it would be a 25ss. Most of the 25XS engines in the beginning were just power heads put on 25ss towers so you may have a 25ss serial number on the sadle and a different one on the powerhead.

[25xs]

Cooper,

I believe if it's a 25 "XS" engine, then your serial tag is from an earlier 25 "SS" engine... The swivel & clamp ass'y, exhaust tower & gearcase from a 25 "SS" engine can be used under a 25 "XS" powerhead if the right tuner/adapter plate is used.

The first year of 25XS engines used the later, stronger style, "square exhaust" 25SS exhaust tower & gearcase. A "very" special tuner/adapter plate mated the relatively new, 24.4 cu. in. looper powerhead to the mid & lower and the engine had a 2-piece fiberglass lower engine cover and fully enclosed fiberglass top cowling. The looper powerheads have an aluminum disk pressed into the cylinder block with a serial number stamped in to it. It's a quarter sized disk, but the block likely has been replaced several times.
The following year, the 25XS used the same 9inch exhaust tower & clamps as the newly introduced 44XS .

The 1985 "25XS" engines had serial numbers starting with 85A001 consistent with the format of the 25SS engines...

The1986 run of short 9inch tower "25XS" engine serial tags were located on the new style (looper) swivel bracket with the modern (current) Mercury 8 character serial number where the second character is a letter and the rest are numeric (e.g. 0A123456) This swivel bracket & clamp assembly is also the 44XS part.

The very last 25XS sold by Mercury Performance Products was March 14, 1995 and was Serial No. 0D937381 for $2,400 +tax

[Steve Bork]

I remember Mercury changed the 25XS blocks to a different casting so we sent in our 1986 block and they sent new blocks in an exchange program. Mercury sold lots of 25XS and 44XS with the East and West coast Mercury challenge racing series.