Re: trying to get 500 more rpm.
Engine is runnig good as is . 5.8 omc at wot i am at gps 35mph at digital 4000 rpm on very choppy water. prop is aluminum 4 bld 15X16. boat is 24ft 2455 normal weight is probably around 7000lbs. i know recomended wot is 4500. should i leave it alone or can i make some adjustments like change timing to get the extra rpms.
Howdy,
This is really a Prop Forum question/issue if your engine is otherwise running correctly..........
But have a look at
http://forums.iboats.com/omc-i-o-in...have-technical-information-diyers-468655.html
Focus particularly on #14
If your engine is running correctly and you have the correct drive (most 5.8L engines use a 1.41:1 ratio drive) on the back, you're "over-propped".
All engine manufacturers (including OB makers) suggest selecting a prop pitch that allows operation in the operating range of the engine and specifically at the top of the range when lightly loaded, operating at the MSL PA (Mean Sea Level -Pressure Altitude) you'll normally operate.
If the WOT RPM is
below the normal operating range, AND you're running "right" (good compression, timed correctly, carb/fuel sys "ok", fresh fuel, not over-loaded or dragging an anchor, etc) you're still "lugging" the engine and you need a lower "gear"........
I.E. a lower pitch prop
