250 ox66 max rpm

**rob.b.** · 08-26-2024, 08:22 PM

Anyone know how to prop these things? Yamaha says 5500, the limiter is 6050. The boat is doing 66.5mph at 5700rpm (per the ****ty Yamaha digital gauges, so it could really be anywhere from 56 to 5800 they take forever to register a number) with 23 mirage plus with the engines pretty far down in the water, maybe 3 or 4 inches below the boat with a foot of setback. Doesn't seem to want to rev any more then that, I can trim to where the boat is barely starting to porpoise at that speed and rpms don't go up, goes the same speed trimmed up or down. Takes off like a ski boat with all the vent plugs in, could take more pitch just wondering if these engines are supposed to be able to go to 6k.

Also, I know, I should throw them away and get some mercs.

**aj06bolt12r** · 08-27-2024, 06:13 AM

Sounds to me like the setup you have is pretty good. Keeping the engines in the meat of the power band and holeshot is excellent. Might not be any reason to mess with anything..

Of course if you want to tinker with it you can start going up with the engine height until some undesired characteristic presents itself... Something like poor hole shot. Loss of bow lift. Loss of bite in rough seas.. ECT..

If raising the engines results in higher RPM and higher top speed.. Good.. You might end up on the limiters and then need higher pitch props.. If raising the engines results in higher RPM and no gain in speed.. Well.. You tried.

**allstock** · 08-27-2024, 08:46 AM

Those are great engines, very reliable if looked after. They will run out of oompf at 5900 rpm so no point in looking for the limiter. 57-5900 is ideal.

**rob.b.** · 08-27-2024, 07:59 PM

They feel like they run out of power at 5500 and are just kinda rolling over after that. Just making sure this is normal before going with more prop. I've done all the usual maintenance new 02 sensors, fuel pumps, filters, plugs ect.

With the engines 2 inches lower it was doing 64 and the slip was really low, little better midrange cruise, much better holeshot, extremely poor handling. Was thinking 24 bravos and move up an inch see how that does. I think I'm a fuzz too high for these props they blow out if you full throttle it below 30mph, turn to hard, running fast in rougher water ect.