04-30-2025, 08:15 PM
(04-30-2025, 07:58 PM)Paddler Wrote:(04-30-2025, 07:32 PM)BYUHunter Wrote: That motor should be operating between 5300 and 6300 RPM at WOT. Most recommend leaning towards the higher end of the range, particularly if you are at the lower elevation range of where you'll be fishing (you'll lose power/RPM as you go higher).
You should pick up about 200 RPM for every inch of prop pitch you reduce. I would drop the prop pitch 4" to 5" to hopefully get to around 6K RPM. This should also help with the prop torque or "lean" that you are experiencing.
As for sharing "house" and "starting" batteries, your gut feeling that it won't work long term is probably correct. The new fish finders these days pull a lot of power, especially if you have FFS. Add to that radio, nav lights, electric downriggers, and any other draw, and the battery may not last very long. I have my starting battery on an isolator from my house battery, which means once the starting battery has 13.6v, it sends any additional power (via the alternator) to the house battery. This is a one-way relationship. This way, even if you run your house battery dead, you always have a fully charged starting battery.
I agree, dropping 4" should be about right if your current WOT is only 5000RPM. My boat and motor with gear probably weighs close to 2500-3000#, more with full ice (120qt plus 150qt coolers full) and fuel (52 gallons) on a 140 mile tuna trip. I'm running a SS Mercury Enertia 16P prop and can hit at least 5500RPM.
I pretty much only troll and don't turn off my engine very often during a typical day of fishing. I've always run just one battery and run my FF/GPS, downriggers, autopilot, radar, etc with no problems. I don't have a bow mount, don't need one my my style of fishing.
A shared house-starting battery would work fine if you rarely turn off the main, and therefore have a fairly constant supply of alternator power.
I think for Dubob's application, where he shuts off the main and trolls with the bow-mount, and ostensibly runs off of battery power for hours at a time, it would make me nervous.