Prop to Pad height - lower?

[Gitzit1179]

Hello, I just repowered my 181DC to a new Mercury 4S PRO XS 150 hp. It has a 6" CMC jack plate (manual), 23p Tempest in good condition and is 4 1/4" below pad. She gets out of the hole very quickly and needs very little trim to get up on pad. Slightlly overtrimming will produce a chine walk. Myself, half tank of fuel and all my gear gets me about 55 mph at 5600 rpm. My previous 2-stroke Mercury with the same setup got me around 59-60 mph (no jack plate). I would like to squeeze a bit more out of her - so if you were me would you raise the motor and what height would you raise it to?

[STLBassBuster]

Start raising it 1/4" at a time. Watch the change in rpm and water pressure. You don't want your water pressure below 10 PSI at full tilt. You will probably end up between 3.5-3 below pad.

[Gitzit1179]

Start raising it 1/4" at a time. Watch the change in rpm and water pressure. You don't want your water pressure below 10 PSI at full tilt. You will probably end up between 3.5-3 below pad.

Thanks. I had the motor bracket on the wrong bolt holes relative to the jack plate so I've corrected that plus I dialed up the prop relative to the pad on the jack plate itself. Now at about 3 5/8" inches. Will try that P-t-P height and see how she scoots. I don't need to set the water on fire, just trying to squeeze a bit more out of her. This repower has breathed new life into my Champion - I may never get another boat!

[tj]

PTP is 3.78-inch for > 1985 184 Champ dual console, 1997 Merc 175 EFI, 1997 A45 25P Tempest, 2003 CMC ML-65 5.5-inch manual jack plate, 65GPS@5600
[ 5000-5600 max RPM at full throttle, 97 brochure ]

So mine runs good about 3-6/8 PTP; and yours is 3-5/8.

dry weights: from Mercury Marine website & 1997 Mercury Outboards brochure
- new PRO XS 150 4S 456#
- 1997 150 1998cc 408# (carb)
- 1997 150 magnum 2507cc 390# (carb)
- 1997 150 EFI (or my 175 EFI) 2507cc 407#
[maybe Lithium tm batteries to get less weight??]