I have a '93 260 with a 502 in it now. When I got it back in '98 it had the stock 7.4L. With a 21 degree Mirage I was getting 55mph on GPS at a little over 5000 rpm. You have to trim the drive up quite a bit to get the most out of it. I would recommend checking the timing at 3600 and see what you get. It should be 34-36 degrees before TDC. Also, a can of Seafoam in the gas tank wouldn't hurt. Something is wrong. It should run more than 4600 rpm at WOT.

I would say tank was 1/2 to full since i never let it go much lower. Love the 302 as it handles the rough water of the lake i boat at. With the 302, i still get the great cockpit space and it has an ac also for overnight crashing. Wasn't really looking to trade up when it happened, just everything worked out perfect as friend bought my 260 without ever having to put it on the market.

u sure it was over 5k, seems unlikely for 7.4 to achieve 5k w/ that prop or in general.

It's been a few years but that is what I remember. Like I said, to get that speed I had to trim the drive up quite a bit. Timing at 36* before TDC and 89 octane gas just for insurance. Motor ran great when I took it out. Just sold it last year to a guy who put it in a motorhome. Good luck.

So i replaced all gas, used 98 octane had carb rebuilt and boat runs great at 10 degrees timing, still getting 4600 max rpm. Boat still runs at 44 mph top end WOT. Not that I will run at that range, Mid range still feels too high to run at and slow. Enclosed pic of Bams Prop Calculator. Slip seems horrible at 28 %. Any ideas. Took prop to a very good prop guy, he claims prop looks fine, almost new. Though only a Mirage, not a Mirage Plus. Any help appreciated.

found a Rev 4 unexpectatly and had it labbed locally by an old timer down the street...
fyi
Stock Michigan SS 19 39mph 5200rpm max (slips, needs planing help)
Stock 21 Mirage 43mph 4600rpm max (slips, needs little tabs, maybe damaged prop)
More cupping added 21 Mirage 47mph 4500 rpm max (slips, needs little tab)
Rev 4 21 Stock 48mph 4600rpm max (no slip, nice accel, little bow lift, no tabs needed)
Rev 4 21 Labbed 53mph 4900rpm max (no slip, nice acceland and cruise, bow lift much better, no tabs needed for plane, rpm too high)