I need to know if it`s any difference in hight of the outgoing shaft on an old oil pump part #.827643 and a new oil pump part #.8M0051418 ? Main problem is the hight of the oil pump drive # 881669 driven by the cam,I feel the oil pump drive is to deep in the block and not hitting the cam drive propperly .It is the newer type 525 EFI .Thanks.

For the drive pump, it looks like they have 2 designs for the mounting hardware...Not sure if they're interchangeable or not but in the link below if you look at item numbers 26 - 35 you may see something that you're trying to figure out on the top side.
http://www.mercruiserparts.com/Show_...nd+Camshaft%29

Looks like they switched oil pumps almost around the time they switched the mounting hardware on top.
http://www.mercruiserparts.com/Show_...n+And+Oil+Pump

Let us know, good luck.

Thanks for reply Lakematdude,you are right they did switch to another oil pump and part #,I did sort it out with mesuring the drive hight , it`s not posibel to go too deep with the oil drive,the oil pump shaft will set the hight.
Have a nice spring and boating