I trust you are well.
I would be very happy if you could give me some advise on propheight. I have a PM 25 with twin Merc 2.5 EFI SS engines.
I have mounted the engines directly on to the transom. The engines have 2 inches built in setback. Current propheight is 1,2 inches below the transom. I use CLE lower units. 1.87 ratios.
I have only got hold of two different props; Bravo 28 x 14,5 and Mirage Plus 14,4 x 27 pitch. Top speed with the Bravos was 84 mph at 6.300 rpms and with the Mirage Plus top speed is 86/87 mph at 6.800 rpms. Over these speeds the boat requires more bowlift, and the props loose bite and rpms climbs with no more speed.
I am spinning the props inward.
Bravo is a bowlifting prop, but the 4 blade create transomlift too. The Mirage Plus is a low rake prop with large blade area. I think these are the reasons why the do not fit.
Its very difficult to get hold of props to test here in Norway. I will try to get hold of two Chopper 28 props. Maybe a pair of ET's too. Or Raker props... What do you think?
Or should I add 2 inch setback spacers. This will lower the propshaft 0,5 inch and give a little more lift. Or is the correct prop the key answer?
Cheeeeers, Toffen G