I was wondering if this mod will also slow down cargo ships from https://mods.factorio.com/mod/cargo-ships as they are based on trains. I'm hoping it does as that would be awesome.

probably

I will experiment with this later this week and update this thread with my findings.

Necroposting a 5-year-old thread because it's the only one relating to using it with the Cargo Ships mod, there was never a reply as to if it ever worked, and there's a crash using the two mods together on the latest version lol
happens as soon as a cargo ship starts moving, both manually and automatically. I like both mods equally, so aside from requesting a special update just for me, got any suggestions as to how I can just... edit the mod to not affect cargo ships, to get around the problem?

The mod Overloaded Trains (2.0.10) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event OverloadedTrains::on_train_changed_state (ID 31)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'index'
__OverloadedTrains/control.lua:392: in function <OverloadedTrains/control.lua:277>