I am looking to replace a Shimano M151 crank. I want to get something that is compatible with the current bottom bracket, which seems to be fine (no noise, no wobble, little resistance).

How can I tell what I can use to replace the M151? Here is a link to the specifications:

https://techdocs.shimano.com/media/te...9830657743.pdf

The bike is a Cannondale Quick 5, bought in March 2009. I'm not sure if it is a 2009 or 2008.

Thanks in advance!

cranks have profile types , the design is around how the planes where the chainrings sit is in relation to the length of the BB spindle ..
so some were designed to sit on a short spindle, some a long one , and generally ends up with chainrings in same places ..

not working in Shimano engineering ,,

did use a M730 crank on a 118 spindle on a touring bike setup

another is on a 127.5 axle with 1 chainring on the middle position (Rohloff 16t, chainline.. )

IDK , not online anyhow ..
Cannot be the free clairvoyant .. assemble choices in the same room and try them .. re sell wat you dont like ..

Thanks, Bob.

So if I understand correctly, I can use any crank that uses the same length spindle as the M151 uses. Right?

Looking at the specs I attached to the OP, the spindle length is "D-NL (122.5 mm)". What does the D-NL mean? Can I choose anything that uses a 122.5 mm spindle, or do I have to match the D-NL part too?

Their codes ? No clue .. write Shimano Irvine Cal is their HQ in USA .. D-NL is that on a loose ball BB spindle ?

the other part of crank positioning is in line with the rear cassette stack so the middles of both line up ..

unless you intentionally want different like a centered big ring and a bail out little one ..

Center on doubles is usually the spider between the 2.

The D-NL is just their designation for their 122.5mm spindle.