I have a 18 foot aluminum Fisher, SV-18CC with a 1990 3cyl 90hp Mercury. It weighs about 700 lbs, the motor is about 280lbs. I don't have any good props to run with this setup. I had an old 21 inch aluminum prop that I threw on there and it ran like crap. 31mph at 4200 rpm... The old motor was a 75 Mariner and I ran a Powertech ELD3R 17 at 34mph at 5000 rpms.
Looking for a prop suggestion. Thanks in advance.
I was hoping that you had an Optimax and I'd be able to help. Do you know the gear ratio in your lower unit?
2018 Ranger RT188 SC Black/115 hp Yamaha SHO 4-stroke; Garmin LVS34 - north
2018 Ranger RT188 DC Black/115 hp Merc Pro XS 4-stroke; Garmin LVS34 - south
14' Mirrorcraft tin boat (ancient) with a 9.9 Mercury 4-stroke, no electronics; catches fish anyway
2.3:1Originally Posted by tcesni
I have a 18Ft Design Concepts. Similar boat. 15 pitch $ blade is what i run but i also have a 16P mercury vengeance that is absolutely perfect. I would try a 15.
A 19 or 20" pitch stainless 3 blade.
I'm already running a 16 and it's spinning way too fast, if I go down to 15 I would be way over revs
I'm looking
Same ratio as the Optimax, I run a 22” prop and max out at 5400 rpm which is 350 rpm below my limit so I’d think you’d need a 20 or 21” prop for your boat and a 22” isn’t out of the question as your boat weighs 500 lbs. less than mine.
2018 Ranger RT188 SC Black/115 hp Yamaha SHO 4-stroke; Garmin LVS34 - north
2018 Ranger RT188 DC Black/115 hp Merc Pro XS 4-stroke; Garmin LVS34 - south
14' Mirrorcraft tin boat (ancient) with a 9.9 Mercury 4-stroke, no electronics; catches fish anyway
I'm picking up a 19 inch black max today, going to give that a try. I already tried a 21, I was the first prop I tested. But in hindsight I really had the boat loaded that day and maybe it was an unfair test.
Boat is 700lbs
Motor 280
People 400-500
Gas 72
Gear 50
What's your speed with that setup?
One person, Light99F7BA69-B3A3-4283-A14E-134000EE728F.jpeg chop, full tank of gas and empty livewell.
2018 Ranger RT188 SC Black/115 hp Yamaha SHO 4-stroke; Garmin LVS34 - north
2018 Ranger RT188 DC Black/115 hp Merc Pro XS 4-stroke; Garmin LVS34 - south
14' Mirrorcraft tin boat (ancient) with a 9.9 Mercury 4-stroke, no electronics; catches fish anyway
Awesome!
42 during the summer is typical but with the cooler air and water temps it was feeling frisky last week.
Well, picked up a 19 inch black max this morning, put it on when I got home. Tomorrow's trip will be with three guys all together, and three people's gear so it should be a good test for the 19, if it performs well, I'll throw the 21 on because I usually just fish with one other guy. I'll wait and see what the RPMs are at Full Throttle
Last edited by leckbass; 10-30-2021 at 08:44 PM.
so I picked up a 13 x 19 Black Max, tested it today. Had three big guys, 225 each, 12 rods, gear, etc... 4900rpms at 32 mph, terrible... I'm going to run it again on Tuesday afternoon with one other guy and less gear, I'll see what happens
I can't believe going from a stainless Powertec and 17 to the Black Max 19 drop my RPM's almost 1000, can the third guy in the boat really make that much of a difference?
Are you trimming up?
We are missing something somewhere. What is the diameter of your prop? I know that an aluminum prop will flex more than a stainless prop and lose rpms and a 3rd guy might make a big difference if the boat struggles to get on plane. Since I really need to spin my motor to higher rpms, I borrowed a neighbors stainless prop that wasn't a Laser II, some sort of "economy stainless" prop, and it ran terrible on my boat even though it was 20" pitch compared to my 22". Its like voodoo science. Will be interesting to see how it runs with 1 or 2 people on board.
Definitely trimming up, but I get to the point where the boat just porpoises
The Black Max is a 13 by 19, the power Tech was 13.25 by 19
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