MerCruiser 5.7
250 HP · Raw-water (seawater) cooled as standard, closed cooling optional
The MerCruiser 5.7 is a 250 hp petrol V8 sterndrive built on the GM 350 cid small-block, and the standard big-engine option in a generation of cruisers, deck boats and larger runabouts. It was sold in carbureted (TKS) and fuel-injected (MPI) forms behind either an Alpha or a Bravo sterndrive, and that drive choice decides more of your service parts than the engine does — including where the raw-water pump lives. Maintenance runs on a 100-hour or annual cycle, with separate 200-hour and 300-hour buckets for drive-level work. Below are its published specifications, Mercury's maintenance schedule, and genuine service-part numbers.
Specifications
| Engine type | V8, petrol, four-stroke |
|---|---|
| Displacement | 5.7 L (350 cid) |
| Bore × stroke | 102 × 88.4 mm (4.00 × 3.48 in) |
| Rated power | 186 kW (250 hp) — SAE J1228 / ISO 8665 crankshaft power |
| Specified WOT rpm range | 4400–4800 rpm |
| Idle speed in neutral | 650 rpm |
| Minimum oil pressure at idle | 28 kPa (4 psi) |
| Thermostat (raw-water cooled) | 71 °C (160 °F) |
| Ignition timing at idle | 10° BTDC |
| Firing order | 1-8-4-3-6-5-7-2 |
| Spark plug | AC MR43LTS, or AC 41-993 platinum |
| Spark plug gap | 1.14 mm (0.045 in) |
| Engine oil capacity (with filter) | 4.25 L (4.50 US qt) |
| Engine oil | Mercury full-synthetic MerCruiser engine oil, 20W-40, NMMA FC-W rated |
| Seawater cooling system capacity | 20 L (21 US qt) — winterisation reference |
| Closed cooling system capacity | 18 L (19 US qt) |
| Alternator | 65 A |
| Recommended minimum battery | 375 CCA / 475 MCA / 90 Ah |
Maintenance schedule
MerCruiser's recommended service intervals for this engine. Most items are time-or-hours, whichever comes first — boats that sit still hit the calendar interval long before the hours.
Each day, before starting
- Check the crankcase oil level
- Check the sterndrive gear lube level
- Check the trim pump oil level
- Check the power-assisted steering pump or compact hydraulic steering fluid level, depending on your steering system
Each day, after use
- If operating in salt, brackish or polluted water, flush the seawater section of the cooling system after each use
Weekly
- Check the water inlets for debris or marine growth
- Check and clean the seawater strainer, if equipped
- Check the coolant level
- Inspect the sterndrive anodes and replace if 50% eroded
Every two months or 50 hours, whichever comes first
- Lubricate the propeller shaft and retorque the nut (freshwater-only use may extend this to every four months)
- If operating in salt, brackish or polluted water, apply Corrosion Guard to the power package
- Check the battery connections and electrolyte level
- Check that gauges and wiring connections are secure, and clean the gauges
Once, after the initial 20-hour break-in period
- Change the engine oil and filter
- Change the sterndrive gear lube
- Touch up the paint on the power package
Every 100 hours or annually, whichever occurs first
- Change the engine oil and filter
- Change the sterndrive gear lube
- Replace the water-separating fuel filter element
- Retorque the connection of the gimbal ring to the steering shaft to specification
- Check the steering system and remote control for loose, missing or damaged parts; lubricate the cables and linkages
- Check the continuity circuit for loose or damaged connections, and test the MerCathode unit output on Bravo models
- Clean the flame arrestor, the IAC muffler (MPI engines) and the crankcase ventilation hoses; inspect the PCV valve if equipped (on V6 models the PCV valve is a non-serviceable internal part of the valve cover assembly)
- Inspect the condition and tension of the belts
- Check the coolant level and antifreeze concentration for adequate freeze protection
- On driveshaft extension models, lubricate the driveshaft U-joints and the tailstock input and output bearings
- Touch up the paint on the power package
Every 200 hours or 3 years, whichever comes first
- Inspect the U-joints, the splines and the bellows, and check the clamps
- Check the engine alignment
- Lubricate the U-joint splines and cross bearing, if equipped with a grease fitting
- Lubricate the gimbal bearing and the engine coupler
Every 300 hours or 3 years, whichever comes first
- Check the engine mount for tightness and retorque if necessary
- Check the distributor cap, if equipped
- Check the electrical system for loose, damaged or corroded fasteners
- Check the cooling and exhaust system hose clamps for tightness, and inspect both systems for damage or leaks
- Disassemble and inspect the seawater pump, replacing worn components
- Clean the seawater section of the closed cooling system; clean, inspect and test the pressure cap
- Inspect the exhaust system components and verify that the flapper valves are not missing or worn, if equipped
Every 5 years (every 2 years if extended-life coolant is not used)
- Replace the coolant
Genuine service parts
MerCruiser part numbers for the routine service items on this engine. Several vary by build date or cooling type — check the note before ordering. Genuine parts are stocked by the MerCruiser dealer network; where a cross-reference is shown, an aftermarket equivalent is also available.
| Engine oil filter | 866340Q03 Mercury's fitment is 'MerCruiser sterndrive and inboard engines except V6 engines with the oil filter mounted on the engine block'. This engine is not a block-mounted V6, so this is the filter. (The block-mounted V6 filter is 883702K — that is the 4.3's part, not this one.) |
|---|---|
| Water-separating fuel filter | 802893Q01 Mercury's fitment covers all MerCruiser sterndrive and inboard engines EXCEPT 1992 4.3L Gen II engines fitted with an inline fuel filter, 1.6L Vazer, and 3.0L MPI. If your engine is a 1992 4.3L Gen II with an inline filter, this is not your part — check the filter mounting before ordering. |
| Spark plugs | 862029 Mercury specifies AC MR43LTS, or AC 41-993 platinum, gapped to 1.14 mm (0.045 in) for the 5.7 TKS. Quicksilver 862029 corresponds to the MR43LTS. A V8 takes eight — order accordingly. Plugs are also included in the 5.0L/5.7L MPI 300-hour engine kit below. |
| Thermostat | 808252T5 / 864493 / 530451 Raw-water-cooled engines run a 71 °C (160 °F) thermostat; closed-cooling engines run 77 °C (170 °F). Confirm which cooling system you have before ordering. A thermostat and gasket are included in the 300-hour engine kit below. |
| Seawater pump impeller — Alpha drive | 8M0100526 / 43026T2 / 817275Q05 On an Alpha the raw-water pump lives in the drive, not on the engine, so servicing the impeller means dropping the drive. Which impeller or kit you need depends on the drive serial number — 0D469859 and later differ from earlier Alphas. The 300-hour figure comes from the contents of Mercury's Alpha One Gen II 300-hour kit (8M0147073), which includes a water pump impeller kit; no maintenance-schedule row in these manuals names a sterndrive water pump on its own. |
| Seawater pump impeller — Bravo drive | 59362A4 / 59362Q08 / 59362T6 Bravo-equipped engines carry an engine-mounted seawater pump, so the drive does not come off for this job. Which impeller you need depends on whether the pump body is the one-piece or two-piece type — check the pump before ordering. |
| Serpentine drive belt | Varies by configuration Belt length changes with power steering, idler diameter and cooling type, and Mercury does not publish a single belt number for the 5.7 by engine model. The 5.0L/5.7L MPI Alpha 300-hour kit (8M0147068) includes the correct serpentine belt for the engines it covers — that is the reliable way to get the right one. Otherwise quote your engine serial to a Mercury dealer. |
| Flame arrestor / IAC muffler filter | Varies by configuration The 100-hour schedule cleans these rather than replacing them, and Mercury publishes no standalone part number for the IAC air filter (it appears only as a line item inside the 300-hour kit contents). No Mercury flame-arrestor listing names the 4.3 L specifically. Clean at 100 hours; quote your serial if a part is actually needed. |
| Sterndrive anode kit | Varies by configuration Anode choice depends on BOTH drive family and water type. Mercury currently publishes magnesium kits for freshwater only and aluminium kits for fresh or salt water, and no zinc drive kits at all — their aluminium anodes cite MIL-A-24779(SH). If you have been told 'zinc for salt', that is no longer Mercury's own guidance for drive anode kits. Identify your drive, then choose magnesium (fresh) or aluminium (fresh or salt). Inspect weekly, replace at 50% erosion. |
| Sterndrive gear lube and drain seals | 858058K01 / 19183Q02 Mercury High Performance Gear Lubricant plus the gear-case fill and drain screw seals. Alpha One capacity is 1892 mL (64 oz), which Mercury notes includes the drive lube monitor; Bravo drives differ, so check your drive before buying a quantity. The seals are single-use — replace them at every lube change. |
| Engine 300-hour maintenance kit (MPI, Alpha) | 8M0147068 Mercury's 300-hour kit for 5.0L and 5.7L MPI engines with an Alpha sterndrive, 2002 and newer — oil filter, fuel filter, gearcase drain seals, spark plugs, thermostat, thermostat gasket and serpentine belt. Carbureted and Bravo-equipped engines take different kits; confirm your engine and drive before ordering. |
| Drive 300-hour maintenance kit — Alpha One Gen II | 8M0147073 Mercury's Alpha One Gen II sterndrive 300-hour kit (1991 and newer) — drive install gasket kit, aluminium anode kit, gear case drain seals, transom repair kit, shift cable kit, water pump impeller kit, and gear case fill and drain screws. This is a DRIVE part, not an engine part; the engine has its own 300-hour kit. Earlier Alpha One drives take 8M0147072. |
What owners watch
The 100-hour cadence is not the diesel 250-hour cadence
Mercury's schedule is 100 hours or annually, whichever comes first, and on most recreational boats it is the annual half that actually fires — a boat used thirty hours a season still needs an annual oil and filter change. The sterndrive gear lube is on the same clock and is the one owners forget, because nothing about running the engine reminds them of it.
Alpha or Bravo changes the job, the parts and the cost
The 5.7 was sold behind both drives, and which one you have decides where the raw-water pump lives. On an Alpha it is inside the drive, so an impeller change means dropping the drive. On a Bravo the seawater pump is on the engine and the drive stays put. It also decides your anode kit, your impeller part number and which 300-hour kit is yours. Identify the drive before ordering anything.
Drive items run on their own clock and get skipped for years
Bellows, U-joints, splines, engine alignment, gimbal bearing and coupler sit in a 200-hour or three-year bucket that is separate from any engine service, and the seawater pump is in a 300-hour bucket of its own. Because these are drive jobs rather than engine jobs they are easy to miss entirely. A split bellows can sink a boat, and the gimbal bearing and coupler are labour-intensive to reach once the drive is off — so they are worth doing together while it is out.
Eight plugs, and the gap is worth checking against your own manual
A V8 takes eight plugs rather than the six a 4.3 needs, which matters when you are pricing a tune-up. Mercury's own spark-plug gap figures vary across manual revisions for this engine family, so use the figure printed in the manual for your engine's serial number rather than a number from a parts site or a forum.
Manufacturer documentation
The figures above are summarised for quick reference. For the full operator's manual and illustrated parts list, go straight to MerCruiser — they keep the current revision, so you always get the right version for your engine.
Mercury serves the correct Operation, Maintenance & Installation manual against your engine serial number. This engine spans many model years, two fuel systems and two drive families — pull the manual for YOUR serial rather than relying on a generic revision.
Other engines in this range
Never miss a MerCruiser 5.7 service
Keeply builds your engine's maintenance schedule, tracks the hours, and reminds you before a service is due. Ask First Mate "what's overdue?" and get an answer from your own records. Free to start, no credit card.
Engine specifications transcribed from Mercury OMW manual 90-899883179 (October 2007), which covers the 4.3, 5.0 and 5.7 TKS; bore and stroke from Mercury's Product Applications manual 90-863758060 (August 2006); fluid capacities from OMW manual 90-899883173 (December 2007) for the 5.7 MPI. The maintenance schedule is Mercury's 'Maintenance Schedule — Sterndrive Models', transcribed from OMW manual 90-864195061 (November 2006) and corroborated against 90-860171061 and 90-899883179. Part numbers are from mercurymarine.com product pages. Compression ratio is deliberately omitted — the only figure found sits in tables for inboard and tow-sports 5.7L variants, not the sterndrive. Figures are for reference only; always confirm against the manual for your engine's serial number before ordering parts or carrying out service.