Yamaha 25 Hp Outboard Top Speed

FishingFleet

Thinking about running a Yamaha 25 hp on a small aluminum rig and trying to set realistic expectations for top speed. I’ve seen everything from 20 to 30+ mph claimed online, but it sounds super dependent on hull, load, prop, and setup. For folks actually running a 25 (two‑stroke or the newer F25 four‑stroke), what GPS top speeds are you seeing and what setup gets you there?

A few specific questions:

What’s a realistic top speed on a 14-16 ft jon/utility/semi‑V with one person vs two, light fishing load?
What WOT rpm range should I be targeting on the Yamaha 25, and which prop pitches tend to hit it on common hulls?
How much top speed did you gain (or lose) from engine height changes (moving up holes, jack plate), trim, or switching from aluminum to stainless props?
Do cupped props help with holding trim without killing speed on these small motors?
Any noticeable speed change from adding a small hydrofoil or smart tabs, or do they mainly help hole shot?
Altitude: how much does it knock off on a 25 hp in your experience?

If you’re willing, could you share your numbers in a quick format? Trying to build a little real‑world reference:

Boat make/model/length/hull type
Approx boat + load weight
Yamaha model/year (2‑stroke or F25 4‑stroke), tiller vs remote
Gear ratio if known
Prop brand/material/diameter/pitch/cup
Engine height (holes up or jack plate setback/height)
WOT rpm and GPS speed
Elevation and typical load (people/gear)
Any handling notes (porpoising, ventilation, chine walk)

Not chasing a unicorn speed, just want a solid, safe setup and a realistic top-end target before I buy.

LighthouseLover

Hey folks, solid thread starter-love seeing actual GPS numbers instead of butt-dyno guesses. I’ve run a Yamaha 25 on a couple small rigs over the years (older 25MLHU 2-stroke and now an F25), mostly on 14-16ft aluminum jons for fishing potholes and reservoirs here in Colorado. Claims of 30+ are usually unicorns: bone-stock 12ft prams with 150lb kids or propped way down for drag racing. Realistic? 22-28mph solo/light on a 15-16ft utility, dropping 3-5mph with two adults + gear. Heavier loads or chop kill it quick.

Quick hits on your Qs from my setups:

Top speeds: 14ft semi-V (like my old Grumman) solo/light ₂₄-26mph; two guys + cooler/rods ₂₀-22mph. 16ft flat jon pushes 27-29 solo, 23-25 loaded.
WOT RPM: Target 5500-6000 on both 2S and F25 (per Yamaha specs). Undercooked props (too much pitch) bog at 4800-5200 and lose 2-4mph; overpropped ventilates.
Height/trim/prop swaps: Moving up 1-2 holes gained me 1-2mph on the jon but needed more down trim to kill porpoise. No jackplate, but 4″ setback helped turn radius. Alum to SS prop (same pitch) = +1-1.5mph, but SS grips better in slop. Trim way up at WOT for speed, but watch ventilation.
Cupped props: Big yes-helps hold plane/trim on small motors without porpoising, minimal speed hit (maybe 0.5mph). Essential on flat jons.
Hydrofoil/smart tabs: DOEL-Fin or similar added _1mph top (better efficiency) but shone on hole shot (+planing threshold down 200-300rpm) and stability with passengers. Worth $30.
Altitude: At 5000-9000ft here, figure 10-15% loss vs sea level (3%/1000ft rule of thumb). My F25 at 8500ft hits same RPM but 2-3mph slower than Denver tests.

My numbers (two setups for comparison-both GPS via Lowrance Hook):

Setup 1

Boat: Grumman 1471 semi-V / 14.5ft
Weight: _350lb boat + 25hp + solo 180lb me/light gear = 600lb
Engine: Yamaha 25MLHU 2-stroke / 2005 / tiller
Gear ratio: 2.00:1
Prop: Solas alum / 10-⅛″ dia x 10.5″ pitch / 2-cup
Height: Stock transom hole (no jack)
WOT: 5800rpm / 25.8mph GPS
Elev: 5200ft / solo or 1+gear
Notes: Solid hole shot, slight porpoise until cupped prop. Great torque for pushing decoys.

Setup 2 (current daily)

Boat: Lowe L1648M flat jon / 16ft
Weight: _450lb boat + F25 + solo/light = 800lb; two adults + cooler = 1100lb
Engine: Yamaha F25SMHA 4-stroke / 2018 / tiller
Gear ratio: 2.08:1
Prop: Michigan Wheel Vortex SS / 10-⅜″ dia x 11″ pitch / 3-cup
Height: 1 hole up + 3″ setback board
WOT: 5900rpm / 28.2mph solo; 24.1mph loaded GPS
Elev: 8500ft / 1-2 people + fishing kit
Notes: No chine walk, zero ventilation at WOT trimmed up. Hydrofoil on lower unit tamed bow rise. SS prop quieter, +1.5mph over stock alum 10.5″.

2-strokes edge out 4-strokes by 1mph top-end but thirstier and louder-F25 more torquey low-end for loads. Y’all running EFI F25s getting better than this? Post pics of your setups/prop stamps if you’re claiming 30+. What’s everyone seeing prop life on these little mills-mine eat rubber every 2 seasons in sandy ramps.

Safe rigging, OP-get it on the water dialed before chasing ghosts. What’s your hull candidate?