Page 118 - REPOWER REFERENCE GUIDE (2020)

Cooling System
Seawater Supply System—Sterndrive

Seawater Supply Connections
All models with the exception of those shown in the following charts come are equipped with a through‑the‑sterndrive seawater
pickup system as standard equipment. Installing the seawater supply system on these models is as simple as connecting a
hose to the transom assembly.
Alpha Models
The cooling system components must be selected and installed in accordance with the following requirements. See the
following chart.
Alpha Models with Closed Cooling

Engine Model Seawater Pickup Requirement
Alternative seawater pickup
4.3L models, 4.5L models, 5.0L NOTE: Bypass the sterndrive seawater pickup system. Ensure that the seawater pickup
models, 350 MAG models, and 5.7L
TKS models hose in the gimbal housing is cut and a block‑off plate is installed to the water inlet on
the transom. Refer to the Mercury MerCruiser Installation Manual.
Specifications—Alpha Models

Alpha Sterndrive Cooling RPM Minimum Flow Minimum Pressure
Models
3.0L (181 cid) Seawater cooling 4000 34 L/min (9 gal/min) Data not available
4.3L (262 cid) Seawater cooling 4000 50 L/min (13 gal/min) 35 kPa (5 psi)
4.5L (275 cid) Seawater cooling 4000 105.4 L/min (23.1 gal/min) 110 kPa (16 psi)
5.0L (305 cid) Seawater cooling 4000 57 L/min (15 gal/min) 38 kPa (5.5 psi)
5.7L (350 cid) Seawater cooling 4000 65 L/min (17 gal/min) 42 kPa (6 psi)
Alpha Sterndrive Cooling RPM Minimum Flow Minimum Pressure
Models
3.0L (181 cid) Closed cooling 4000 Data not available Data not available
4.3L (262 cid)
4.5L (275 cid) Closed cooling 4000 106 L/min (28 gal/min) 138 kPa (20 psi)
5.0L (305 cid)
5.7L (350 cid)

4.5L Alpha Sterndrive Seawater Pump Output for a 15‑Second Period at 1000 RPM
Model Minimum Quantity
Alpha models 4.7 L (5.0 US qt)

Page 4E-6 © 2019 Mercury Marine 90-8M0149179 eng NOVEMBER 2018