What could cause your boat to lose 10mph?

[NickF]

Thank you all for your replies, so to answer a few questions,

Yes those 58mph speeds were off the connect system and it was when I dropped it in fresh off the showroom floor.

I have gone thru 2 full tanks so far this summer, before I dropped it this summer I filled it with 93 (thinking that would help with the fogging oil and stabil that might have been put in the gas tank), the last tank I put in it was 87.

I do have to put a full tank in it again and was going to put 87 from a gas station, not on the water.

The hull is relatively clean, I use to drop and recovery all last year, and so far this year its been in the water for about 2 months (freshwater, but still can see staining forming), plan was to acid wash to see if I get any mph back.

I haven't checked the filters, as the boat was stored and winterized at the dealership at the end of last season. I had the dealership do the "Summerizing" to the boat when I picked it up from them, so I might suspect that they didn't do a whole lot (different story for a different time, just not happy with Nielsen).

The hours on the boat are under 40 for each engine.

The clean out holes are cleared and nothing obstructing, but I plan on pulling it out of the water next week and inspecting everything.

Also no fat chicks, but i was told she's not a lady if she don't weight 280.

Thanks for all the help, I hope to have everything checked out in the next week or so, was planning on it this week, but the rain doesn't look like its going away.

I will post results hopefully if/when I find something.