New Prop. for a Cat. 30

[Kelly]

I am considering putting a new 2 blade 12x13x1 prop on my Catalina 30. The prop was given to me and I would really like to replace the current 12x11x1 prop. I have a 11hp. Universal Dsl engine that runs strong with the current prop. I am concerned that the 12x13 prop might be too aggressive for the engine though. Any thoughts?

 

[Dave]

Check your RPMs

I, too, have a Cat 30 with the Universal 5411 and am running the stock 2 blade prop. The best indicator on whether you can safely make the change to the 2" higher pitched prop is what your top RPM is now. I believe the 5411 (correct me if I'm wrong) is a 3,000 RPM engine. So, if you open her up wide you should just barely obtain 3,000 RPM. If you are propped properly now, switching to the higher pitch prop will overload your engine. This can cause some bad things to happen such as lots of black smoke, carbon build-up and overheating.  My boat seems to be perfectly propped with the stock 2 blade. I can cruise at 5.3-5.5 on flat water and top out just above 6 knots at WOT on flat water. So, this is an indication of the speed you SHOULD be able to obtain if your boat is properly propped with a 5411. Of course on rough water, that speed is GREATLY reduced. I've been told that switching to a 3 blade with 1 inch LESS pitch might be a good idea for powering into wind of heavy seas. But this will cut my sailing speed by 3/4-1 knot. Tough decision....

 

[Dave]

Check Torreson Marine

Follow the link to Diesel Direct at Torreson Marine from the home page here. They have a chart that lists the various size props that can be used on different engines. Dropping down 2 inches in pitch means may make the engine rev too high for the same speed.Dave