My Freedom 25 has a 1GM Yanmar (6.5 hp/3400 rpm) and when I’m motoring the “sweet spot”, where the motor and boat seem to be doing their best, is just over 2,000 rpm and 3 knots. If I increase the rpm I get a lot more noise and vibration, but hardly any more “speed”.
Is three knots a typical motoring speed for a Freedom 25? The Yanmar gets me in and out of the marina just fine, but it would be nice to get a couple more knots out of the combination when becalmed with a distance to go. 
The sweet spot on my F25 was at 2400 rpm with a speed of 4.5 knots
Happy sailing
Jim D
If I recall it should be 85% of the max continuous RPM. Max is 3600 (I think), so cruising should be around 2800 to 3000. Vibration could be a shaft alignment issue. Not a big deal to address.
The design water line for the Freedom 25 is about 20’. I measured the scum line on mine from stem to stern and this is about right. For a 20’ DWL, the hull speed is just about 6 knots. This is the speed where the bow wave is as long as the boat, and as you go faster, it requires more and more energy. 75% of hull speed is 4.5 knots. I used to have a Honda 9.9 outboard, and it could easily (~75% power) push the boat to 7 knots in flat water. Flying the spinnaker in 18 knots deep reaching I have seen above 8 knots.
The power the engine develops is not the power that gets transmitted to the water to propel the boat. There is an efficiency factor that accounts for losses along the way. A typical number for the “propulsive efficiency” of an outboard gas engine is about 38%, which means a 6hp motor only applies about 2-1/4 hp to moving the boat along. Doesn’t sound like much, but based on measurements I’ve made of my hull, it should be enough to push along a 4000 lb displacement Freedom 25 at over 6 knots, at full power, in calm conditions. At 50% power, you should still see more than 5 knots in calm conditions.
Waves and wind can increase drag quite a lot; maybe a factor of 4 or 5 time more power is required for the same speed. If you are only seeing 3 knots at 75-85% power, that might be the issue. If you are only seeing 3 knots in flat water, sheltered from the wind, then you might have a problem.
I used to run at ~ 2600 but now hang at ~ 2200 and 4.5 knots in flat water. I did have to power home in a heavy sea at one point coming back from a regatta that was canceled for too much wind, in waves I was often down to 1.5 knots.
My F25 cruising is 3.5 knots at 1,800 rpms can go for ever, I can rev higher to get more speed but not worth it for me unless on a long delivery with no wind. my max GPS speed is 9knots this was with no kite. This last weekend with my new sq top main I was easily doing 4.5-5knots upwind main alone in 12-15 knots win speed. this was with rotating mast set at 45 degrees, and back stay set for no mast bend, boat was locked in and super easy to sail.
cheers,
yarrow
My 84 25, round mast easily does 5.5 knots at 3,000 rpm. Could the problem be with the folding prop?