Right prop for Yamaha 115

[Bushwacker]

Chance, I ran a 115 Evinrude on my boat for about 30 years and a 13 3/4 x 15 OMC SST was the perfect prop for it. That prop has a lot of cup in it and I was able to raise motor so AV plate was about 1" above keel. Motor had a 2.0:1 gear reduction and would turn about 5500 with a very heavy Bahama-trip type load, carrying about 80 gallons of gas. That was a 300 lb motor, so I could plane at about 12 mph with a heavy load and trim tabs, and run about 32-34 mph WOT depending on load.

However that was a 1975 vintage motor, back when they were rated at the powerhead, so it probably wasn't much more than 100 hp at the prop. Your newer motor is stronger since it's rated at the prop and your boat is probably lighter than my Seafari, so if you have a similar gear ratio, you should be able to run more than 15" pitch. You didn't say what specific prop you're running, but if you're turning 5800-6000 with it, you should be able to run 17" or maybe even 19" pitch, but I'd start with 17". If that motor isn't much over 300 lbs, I wouldn't think you'd need a 4B prop unless the boat is stern heavy for some other reason.