Welcome and WOW!!
You bought a bucket of parts
Is it a carburetor or injection engine?
To find the year you need the VIN or Vehicle Identification Number, it should be on a metal plate as far as i know on all SH models the plate can be found near the gas tank on the frame, if there is no plate there should be also a stamped code in the frame tube somewhere over there.
With the VIN code you can find out the year,you only need the "ZDCKF04A0
1-2-3-4-5-6-7-8-9" part ,usually the red number is the year, in ZDCKF
XX the 2 XX is the series/type , if this doesnt work simply google and if your lucky something comes up, if not you will have to research one of the links below given and search year after year of SH model until you find it.
Service manual in electronic form (pdf) have never been officially released (for customers) by Honda but a paper version can be bought although i dont know if one exists for the carburetor model, google for "hayes service manual" or go to your local Honda dealer.
There are 2 PDF's floating around on the web for the 2006-2008 injection model, one is italian the other is english but "locked" with the "FOPN_fLock security" scam which is used by a ebay scammer to sell a service manual which only "works" for a few months and still is not printable,after the few moths the manual is locked and no more accessible, dont buy a PDF or CD on ebay, or actually; dont buy a PDF or CD at all, its the same guy.
I managed to hack the file, if you have a injection model send me a mail and you can have it.
If you have a carburetor model this service manual will do you no good and is useless for you.
In my months during search i never found a SH manual for the carburetor model but if it is information on the engine youre after you may do a search for the following models as they have the same engine: @ (yes the model is called "@" ), NES, SES,Dylan, Pantheon,Scoopy, and a whole bunch of other names of scooters which have this engine.
[edit] lucky lucky for you, i almost forgot i had it; i have a ,sort of ,service manual in italian for the dylan/@/ pantheon/early SH carb model.
It shows different models and years throughout and has exploded parts views (no part nr's) and is clearly a homebrew labour of love but may be be of some use to you, it is a "text type" pdf (not a scan) and so text can be copy/pasted in google-translate.
If you want detaild exploded views look here;
http://www.oemmotorparts.nl/oem3.asp?M=Honda&T=SH150 or here:
http://www.bike-parts-honda.com/honda-m ... -2003.html