A buddy of mine just put in a new 415 HP, Merc 502 Mag MPI CPO bobtail engine package in his 1990 250ES.

We installed a box stock 25 Mirage Plus. Only pulls 4500 rpm, speedo just a tick over 70 with one person chock full of fuel.

I think we need more rpm, 5000? Any suggestions for other 250/270 owners?

Thanks,

Kurt

Kurt, I ran a 21 Mirage Plus on my 250ES w/ a modified 454 Magnum. I would think you might want to try a 23 Mirage Plus and maybe a plain 23 Mirage if they are available to test. I would agree that you should be at 5,000 RPM. I think your speed number is pretty impressive.

send the prop to bblades to have it labbed that will get you 300rpm when full of fuel and more speed, 4800 and maybe 49 to 50 with half a tank. I had the same motor but carbed in my 24ol would get 4700 with stock prop. if you drop down to a 23 4800 you will loose speed from the labbed prop but be about the same with non labbed. and forget about the speedo there off by 2 to 4 mph you need a gps speedo for true speed. I had two friends that had that boat one with the 365hp 454ran a 23 and other with the 502 he ran a labbed 25 if that helps. art kurt I never got back to you to day hahha, talk to you in the morning about the cockpit rug I will try to get it to you before you leave for out west it will be the temp rug later art

Was that 70 MPH on the "Dream O Meter". You should probably have a 23 pitch Mirage on the boat. Get a GPS you will be lucky to see 63 MPH. Not trying to be a smart a-- I used to do the same thing. I told everyone my boat did 60 and when I got a GPS it really did 55. Now I got it up to 69 GPS 4900 RPM with Lab finished 25 pitch.

With one person, full fuel (100 gals) and 25 Mirage Plus it ran 67.6 on gps @ 4900

I guess it's running pretty good for a stock 502