Speed under power (BMW D7)

[Rhys05]

Just wanting to find out what I should be able to do under power with the D7. I've got the (what I assume is) original Martec folding prop on it. It seems like it doesn't rev nearly as high when under load as it can when out of gear, which seems to me it might be overpropped...but...I can't be sure due to no tachometer (anyone know how to add one to this engine?). I can usually get ~5.4 knots at nearly fully throttle on flat water with little wind, which seems kind of low since hull speed should be around 6.25 knots. Bottom isn't racing clean, but not bad either. Thoughts? Input?

[stephenrwallace]

5.25knot sounds to slow for your diesel. Am able to get 6.25kt in flat conditions with my 5hp Nissan 4 stroke with hi-thrust prop. The diameter and pitch are usually stamped into a conventional bronze prop--don't know about Mar-tek folding. With that info, you could contact manufacturer or Michigan Wheel to be assured that prop is sized right for displacement and hp.