some essencial resources on engine
knoledge for Day skipper and yachtmaster

engine and boat checks

Engine checks

Fuel economy

Volvo marine engine

https://youtu.be/u5Y2T-NTLkc?list=PLHwEfFYvn0F04wGIjls6-D4RL8V6WDPSr

another volve engine
https://youtu.be/oHqrq3ptxC8?list=PLHwEfFYvn0F04wGIjls6-D4RL8V6WDPSr

fouled props

changing impeller