Are the 525's slow to make power. Have a single in 28', low power until 3000 rpm's and then will spin out the prop. Been told that's typical with a 525. Had engine on dyno looks like @ 2200 rpm is showing 200 hp, @ 3000 around 360 hp. You put 5 people on boat and take's almost 40 seconds to make power to plane out around the 3000 rpm mark, embarrassing

It sounds like you need to try some different props. What are you running for rpms WOT, what boat and what prop are you spinning. Need more info.

28 Bravo 4 blade, 28 Sunsation, and other boats like are running same prop.

For whatever it's worth. I have a 27 Donzi ZR with 496HO. Same prop (5,500 lbs dry weight). I also had trouble getting on plane. I think it's just the design of these smaller single engine boats, where weight is so far back, and power is inadequate. I asked people about going to 525, and most didn't think it would help take-off.

So, I put Mercury K-Planes on the boat. Now, I put them all the way down at take-off and it makes a big difference. Really gets up fast with just two of us on board. Had six on board this weekend, and it takes a little bit longer to get on plane, but still very reasonable.

Do you have K-Planes?

K-Planes help a lot for getting on plan, but if you are blowing the prop out, I'm not sure that will help. I'm not familar with the X-dim on the 28 Sunsation, but you may need to try a 5 blade. It seems like every boat is different. You might want to post over in the Sunsation forum and see if you can get any help.

bob,

Are you still having issues with the Sunny

40 seconds to plane out sounds like a problem to me. And not something that a prop change will fix if the boat runs correctly at WOT.

which 525 ?

Thats my thoughts too, but no codes, 100% available power, ran great on dyno.

Mercury Racing 525 EFI