Page 53 - REPOWER REFERENCE GUIDE (2020)

Propeller Selection

2A184329 and 4400–4800 2A184339 and 4400–4800
below below
WOT RPM 4600–5000
2A184330 and 2A184340 and
above 4600–5000 above 4600–5000
2A184329 and 4950 2A184339 and 4950
below below
Rev limiter 5150
2A184330 and 2A184340 and
above 5150 above 5150
Cruising RPM

Modern inboard engines operate at higher engine speeds than those produced just a few years ago. The materials and design
of the new engines allow these higher speeds without a durability penalty. In fact, overpropping the boat to reduce the cruising
RPM to previous levels will increase the susceptibility to engine damage from detonation and preignition.
The recommended cruising RPM ranges are listed in the following table.
Model RPM Range
3.0L, 4.3L, 5.7L, 357 4V, 357 MAG 4V 3200–3600
4.5L MPI 3200–3600
350 MAG MPI 3400–3800
350 MAG MPI Horizon 3400–3800
Black Scorpion 3600–3800
MX 6.2L MPI, 383 MAG MPI, 383 MAG 4V 3600–4000
MX 6.2L Black Scorpion 3600–4000
6.2L MPI 3600–4000
496, 8.1S Horizon 3200–3600
496 HO, 8.1S HO 3400–3800
540 Bravo 4V 3200–3600
357 4V 3400–3800
4.5L Maximum RPM Specification

Maximum rated RPM
Engine Kilowatts (horsepower) RPM
149 kW (200 hp) 4400–4800
4.5L MPI ECT
186 kW (250 hp) 4800–5200
149 kW (200 hp) 4400–4800
4.5L MPI non‑ECT
186 kW (250 hp) 4800–5200
Boat‑in‑the‑Water Tests

Engine Idle Speed
The engine should idle at the RPM as specified in the appropriate Operation, Maintenance and Warranty Manual with boat in
the water, drive unit in forward gear, and the engine at normal operating temperature. If the idle speed is incorrect, ensure that
the throttle cable has been adjusted properly.
Adaptive Speed Control (ASC) Propping with G3
IMPORTANT: Propping of the boat can be done as normally done with all other MerCruiser products, but to achieve the best
optimum propeller selection you can use the propping procedure with the G3 tool to verify your propeller selection.
NOTE: The following procedure explains propping on an engine with a RPM specification that is 4800–5200. This same
process can be utilized for other ASC engines with a different RPM range. The dynamic principle is the same. Refer to your
engine's wide‑open throttle (WOT) range and substitute the minimum/maximum WOT RPM in the following procedure.
A special propping procedure using CDS G3 should be used for optimum propping.
• Install the best guess propeller.
• Run the engine at 100% Demand Linear (demand request by operator) with optimum trim. The Demand (demand request
by control software) and Demand Linear with Guardian (demand request by Guardian) should both equal 100%.

90-8M0149179 eng NOVEMBER 2018 © 2019 Mercury Marine Page 4B-5