Originally Posted by NickHoult
What do folks think about, between the pulling power of an old 40hp and a much newer 30hp, does the ware and tare reduce power as cylinder psi drops through use?? I.e would a much newer 30 be about as effective as an old well used 40 (1980-1990)?
Late 70's- early 80's motors were measured at the flywheel rather than the prop, so a vintage engine with a 25hp sticker would only be the equivalent of a late 90's 20-22hp 2 stroke.
Your question is virtually impossible to answer, I have a 20 year old engine that sat unused for 20 years, its as good now and as powerful as the day it was produced. However last year I bought a 20hp Yamaha that had had a very hard life, worn gears, poor top end and slow recoil, it was beaten on an identical boat by a 15hp Evinrude
Like all used boat things, only 3 things matter, condition, condition and condition.
To answer your question, a good 1990's 40hp will walk all over a newer 30hp. A knackered 1980 40hp will probably be about the same as a modern 30hp.