I have a Bayfield 25 that's running a bit slow under motor. I can only get up to 2.5 kn - the hull speed is just over 5.5 kn. No known or observable issues with the inboard diesel engine. I've got a Yanmar YSE8 inboard Diesel engine in the boat - 8hp/3200 RPM. I do not know the size of the prop - have attached a pic of the prop that's currently on the boat (installed by previous owners). Any thoughts on why I'm running slow?