Need help identifing a year

I bought a boat that has an 85 hp force it needs water pump but I can't figure out the year because the .i.d tag is worn off any ideas on how to find out the year

This site sells the impeller.
http://www.marineengine.com/parts/sierra-marine/sierra-marine-parts-catalog-00194.htm

If it's an 85 then this is the part #
After 5 posts you can add a picture of the motor.
Until then you can use a photo sharing site to add pics.

The housing can look real bad but still work real good.
The wear plate under the impeller if it has deep grooves, replace it.

What color is the motor? White,is 86 or older blue is 87- 89 85hp
90hp started in 1990

Under the power packs on the block and below the bottom carb
is a foundry stamp, in the center of the stamp is the year.

Sometimes the starter(if original) will have a year written on it?

Thanks a lot I pulled ccarbs off and is says made in USA with s circle under it with 88 stamped in the center so I'm assuming it's an 1988.....t truely appreciate your help