SA
4803 posts
i have come to the conclusion that the prop on my Adams is rather the wrong pitch or wrong diameter.
while running in gear in the berth it is thrusting plenty of water as did my last yacht.
But In my past sea trials I have noted with head wind or punching into over 20 I'm experiencing cavitation/aeration. This also happens when I increase Revs too much before boat speed is achieved.
i guess I will need to take a dive and remove the Prop for measurements. As I can't find the exact hull for this vessel I will have to go on length/beam and tonnage etc to find the correct prop right?
i think I know the awnser increase diameter which adds drag or spend another few boat dollars on a feathering big diameter Prop am I correct?
NSW
1322 posts
Sounds like the pitch may be too fine. Have you got the power/torque v speed curves for your motor?
NSW
1215 posts
I think Yara is on the mark. prop needs deeper pitch. Theres a company in Parramatta in Sydney who can work it all out for you and supply the adjusted or new prop.
TAS
824 posts
Been on board a yacht that did this and it turned out to be flow over the prop.
In the case (Westerly 33 I think) the back of the keel in front of the prop was about half the props diameter and only about 1 foot in front of the prop. The prop just couldn't get enough clear water to grab and the results were pretty much as you are talking about.
In his case he went a larger diamater, shallower pitch so the prop saw more clean water but the motor could still spin it.
