Hello, I have a 1971 Catalina 27 with an Albin 022 engine, that may or not be original. It has a new cam shaft (by the previous owner), installed and does run smooth. That said, whenever I bring up the RPM's and the boat is approaching around 5 knots plus or minus, The engine starts to slip. I think it has a gearbox rather than a transmission. But as soon as I bring the RPM's back down it is engaged and runs fine, This is not a new thing, Its been doing it for a year since I have owned the boat. The Albin guy in Sweden suggested I try Kendall Super D3 motor oil. Which I did.However it is still slipping. Could it be a prop issue
