"LakePowell" wrote in message
oups.com...
I'm thinking of buying a 2001 Monterey 262 cruiser. It has the 375 hp
496 mag in it. Dry weight is listed at 5,500 lbs. Specs say it should
go about 50 mph top speed, but I'm assuming that's under ideal
circumstances and at sea level. Test drove the boat at 4500 feet of
elevation and top speed was 38 and it held 30 mph at 3700 rpm. Does
that sound about right or might something be wrong? Would greatly
appreciate if anyone with relevant experience could help.

Thanks!


What was the engine's RPM at wide open throttle (WOT)? The engine should
turn about 4600 rpm at WOT give or take a couple hundred RPM. I'll assume
you intend on running the boat at Lake Powell, based on your ID. If so,
you'll gain some performance , since Lake Powell's elevation is at 3591
feet. This assumes that your test elevation was indeed at 4500 feet.

The only way to set up the boat properly is to take it out at the elevation
you intend to run at, load the boat as you would normally use it, and then
run it at WOT for a brief period and monitor the tach. Mercruiser specs a
WOT RPM for that engine of 4400-4800 RPM. If you're turning less than that
range, you are over propped and working the engine harder than you should.
Since the engine is fuel injected, there are no adjustments to the engine
that are necessary or possible. The only way to bring the engine into its
recommended operating range is to change the pitch of the propeller(s). If
you need to increase WOT engine RPM, you need to step down in propeller
pitch. I'm guessing you probably have a Bravo III behind that 496 mag. If
so, prepare to spend mucho dinero for a new prop set. Been there.