She is christened

[dubob]

Bob,  If you have the factory prop it would work great at sea level, thats where they test them, some prop calculator are ok, merc has one, you RPMs should be between 5500 and 6k WOT,  what ever pitch prop you have I would drop it 2 pitches, thats most likely the case for the selection you have available, advise stainless and 4 blade, better low end , waay better, I have one you could try depending on you pitch, I always run just below porpoise depending on waves, most efficient, Im guessing you have cable steering from you description,  I bet you dont have all your fishing gear in yet either, more weight to slow you down, I like to have the low end more than top speed, some shops might let you test drive a prop, not sure in your area, I would ask.

My prop is a 12.8 X 17.  I will get a 12.8 X 15 installed and keep the 12.8 X 17 as a spare.  Stainless props are a no go for me for one reason - they don't give at all when contacting rocks and transfer all that energy directly to the lower unit internals.  I have been there, done that at least 3 times.  Repairing or replacing the lower unit is 4 to 10 ($3000) times more expensive than replacing an aluminum prop ($300).  Rebuilding an aluminum prop is about half the cost of buying a new one.

Mine is 2015 ranger vs1780 with a 115, I also have vessel view, Highly recommended, I can read fuel consumption, codes, time to empty, temps, its blue toothed to your phone,

Vessel View has been discontinued and replaced with SmartCraft Connect Module that Bluetooth's engine information to your phone and/or sonar display (if compatible).   I ordered the SmartCraft Connect Module and a 13 X 15 prop today.  Now I have to decide on which app to install on my phone to best access the data.

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I do not have a gas kicker and turn off the 115 when I'm trolling and using the Ulterra Quest for drive and steering.  My lithium's (two 12 v in series) have 140ah to play with and on the first trip used 15% of capacity to run for 3 hours at between 4 and 7 prop speed level maintaining 1.7 mph.

I have one crank battery for the 115 Merc.  I have 2 Cannon Mag 10s and a Garmin Echomap Ultra 2 106SV drawing power from the crank battery.  The sonar lets me monitor the crank battery voltage level.  The draw from just the sonar on my 3 hours of fishing the other day was very little and the monitored voltage level read 12.7 after 3 hours.  I'm guessing I could let that get as low as 12.0 v and still be able to start the 115.  I have a spare Gp 24 battery and a set of jumper cables in the boat just in case.  

I'm thinking also that maybe a jump starter kit might be another option to gain maximum protection will fishing and not running the 115.  Another cheap option would be to run the 115 at idle and slow the boat down with sea anchors thereby keeping the crank battery fully charged at all times.