The most common and most likely answer to this crossword clue is the 8 letter word TOWPATHS
I've seen this crossword clue in Financial Times
T
O
W
P
A
T
H
S
More clues leading to the result TOWPATHS
Buddy explains!
The straight part
We know that "Ways to give boats horsepower" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ways to give boats horsepower = towpaths.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TOWPATHS mean?
TOWPATHS noun- A path alongside a canal or river, originally for horses towing barges, now more often used as a footpath