Re: 2010 lowe fm 165 w/ merc 60hp 4-stroke very doggy getting on plane, prop maybe?
Assuming nothing is wrong with the engine, it's the prop.
I know, because I was in almost the exact situation last year. Picked up an 2005 FM165 with a Merc 60 4-stroke. I was talking to the owner about how fast he could go. He told me ~25-28 MPH with 2 people in the boat. Well that was faster than my 19 MPH on my old Lund, so I didnt think much of it.
Until we got to the test drive part. It was slow to get on plane. I had to shift myself towards the livewell area to get it on plane faster. RPMs were maxing out at ~4500.
Other than that, the boat ran and sounded great, so I bought it...
Did a search on the internet and found talk about props and pitch. The 60 4-stroke is suppose to WOT at 6K RPM and should be low 30 MPH with the exact setup. Found others were using 12 or 13 pitch props. So I go look at my prop and it's a 17 pitch prop! The previous owner installed these fins to help with the planing. The dealer set this boat up with that prop.
It should be listed on the side of your prop. In front of the blades.
Anyways, I bought a Black Max 10 5/8 x 12 P prop off ebay, because it was cheapest at the time.
HUGE difference. Gets on plane quickly. Hitting 32MPH on GPS. Topped out at 34 MPH when the water is smooth. Also right at 6K RPM now when on WOT.
Here is a link to the LOWE forum talking about props.
http://forums.iboats.com/showthread.php?t=250420