Maintenance, Corrosion & Winter
Can You Run Your Boat Engine While It Is on the Lift?
Quick answer
Not as the lift holds it, with the water intakes in the air. Mercury, Yamaha, MerCruiser and Indmar all say the engine needs cooling water at the intakes every second it runs, and Yamaha says never "even momentarily" without it. There are two safe ways: lower the lift until the intakes are under water, in neutral, or fit the flush attachment your engine's manual approves, with the propeller removed. Many larger outboards flush through a port with the engine off, so check the model, and never shift into gear on the lift.
On this page
No, not while the lift holds the boat up with the engine's water intakes in the air. The engine makers agree: Mercury's outboard manual says "Without sufficient cooling water, the engine, the water pump, and other components will overheat and suffer damage," Yamaha's says "Never operate the engine even momentarily without running cooling-water," and Indmar, which builds the inboards in many wake boats, says "Do not run the engine unless the boat is in water." There are two safe ways: lower the lift until the intakes are under water, in neutral, or feed water through the flush attachment your engine's manual approves for running, with the propeller off.
Owners hear both "never" and "just put the muffs on." Each is right for a different engine; the damage happens when one is applied to the other.
- Raised, intakes dry: do not start it, not even for a few seconds
- Speed limits on a hose: idle (Mercury 8/9.9), low speed (Yamaha 60F), 1,300 RPM and never over 1,400 out of the water (MerCruiser 4.3 MPI)
- Engine-off flushing: Mercury 75 to 115 hp FourStroke flush port, "with the engine turned off"
- In gear: never on the lift, in the water or out of it
Safety: Mercury and MerCruiser: "Rotating propellers can cause serious injury or death." Fit muffs or pull a propeller from the swim platform or the dock, never standing in the water or on the cradle under a raised hull. Keep swimmers away from a running engine at a powered dock (see boat lift electrical on electric shock drowning), and remember Indmar's warning that exhaust carbon monoxide is "colorless, odorless and extremely dangerous," most of all under a roof.
Why a dry start does damage
Outboards, sterndrives and raw water cooled inboards cool themselves with the water they float in, drawn through intakes on the gearcase or hull bottom by a rubber impeller pump. Indmar's manual explains why that pump cannot run dry: "This raw water pump is designed to use the water it pumps to lubricate its impeller. Do not run the engine unless the boat is in water. If you run the engine with the boat out of the water, the water pump may be damaged, causing your engine to overheat or start a fire."
So the damage shows up later: the engine sounded fine on the lift, and the overheat alarm comes on out on the lake. Indmar adds that overheating damage "is not covered by your warranty." The forum version is "a few seconds is fine": in one Moomba owners' thread a participant says "just about 10 seconds" does no harm, while others describe an impeller that failed on the first outing after a driveway start. No engine maker gives a safe dry time, and Yamaha's "even momentarily" rules out any.
The two safe ways to run it
1. Lower the lift until the intakes are under water
This works for every engine, and it is the only method for engines whose manual gives no way to run on a hose. The goal is water over the intakes, not a floating boat. Mercury's starting procedure has it as a step: "Ensure the cooling water intake is submerged." For an outboard, a useful mark is the one Yamaha uses for running in a test tank: water "above the level of the anti-cavitation plate," because "if the water supply is insufficient, engine seizure may occur."
- Put the drain plug in. See drain plug in or out on a boat lift.
- Trim the drive down into the trim range so the gearcase reaches the water as the lift comes down, but check that the skeg will clear the cradle's rear cross member and the bottom at full lowering (water depth requirements covers the clearance).
- Lower in short bursts until the water is over the anti-cavitation plate on an outboard or sterndrive. On an inboard, keep going until the boat floats free of the bunks (the reason is in the wake boat section below).
- Neutral, then start, and look for the tell-tale. Mercury: "If no water is coming out of the water pump indicator hole, stop the engine and check the cooling water intake for obstruction." Yamaha: "If water is not flowing out of the pilot hole at all times while the engine is running, do not continue to run the engine."
- Stay at idle unless the boat is off the lift and under way.
Hewitt's 2025 lift guide has you lower until the boat "is no longer resting" on the bunks, and only then "switch on the engine." That is the order for leaving the lift. For a test run, an outboard or sterndrive can start with the hull still on the bunks, as long as the intakes are covered and the shift is in neutral.
2. A flush attachment, if your manual allows running on it
Muffs, or the maker's flushing attachment, clamp over the gearcase intakes and feed them from a hose. Mercury's 8/9.9 FourStroke manual runs the engine on one, and says why: "The engine must be run during flushing in order to open the thermostat and circulate water through the water passages."
The manuals agree on the setup:
- Propeller off first (both). Yamaha adds: "Keep yourself and others away from the propeller shaft."
- Water on before the engine starts, and enough of it. Mercury says to adjust the hose "so water is leaking around the rubber cups to ensure the engine receives an adequate supply of cooling water."
- Neutral, low speed. Mercury: "Do not run the engine above idle when flushing." Yamaha: "Shift into 'NEUTRAL', and start the engine while supplying water, then keep it running at low speed for a few minutes."
The boat stays up, but muffs that slip off or a kinked hose put you back to a dry start, so someone watches the tell-tale the whole time.
Check the model: some engines flush with the engine off
Much of the "never run it on the lift" advice comes from owners of larger outboards, and for them it is accurate. Mercury's 75 to 115 hp FourStroke manual flushes through a connector on the bottom cowl, and step 1 is "With the engine turned off, place the outboard in either the operating position (vertical) or in a tilted position." With the tap half open, water runs through for about 15 minutes. The manual describes no hose running method, so these engines run on a lift only when lowered into the water.
Other large outboards work the same way. In a 2009 Louisiana Sportsman column quoting owner's manuals, the Yamaha F250 instruction for its flush port reads "Do not perform this procedure while the engine is running," Honda's BF135A and BF150A flush for at least 10 minutes without starting the engine, and Suzuki's DF200 to DF250 manual gives both: a flush port with the engine off, or ear muffs with the propeller removed and the engine at idle.
That settles the two answers: a 9.9 hp kicker runs on muffs to open its thermostat, a 115 hp FourStroke flushes with the key off, and neither runs dry. Your manual's flushing page says which you have.
| Engine (manual) | Run on a hose? | Limits stated |
|---|---|---|
| Mercury 8/9.9 FourStroke (1F10201BK) | Yes, flushing attachment | Propeller off, neutral, idle only |
| Mercury 75 to 115 FourStroke (8M0125338) | No method given; flush port with engine off | About 15 min, tap half open, vertical or tilted |
| Yamaha 60F | Yes, flushing attachment or test tank | Propeller off, neutral, low speed, a few minutes; tank water above the anti-cavitation plate |
| MerCruiser 4.3 MPI sterndrive | Yes, flushing attachment on the drive's pickups | Propeller off, neutral, 1,300 RPM (plus or minus 100), never over 1,400 out of the water, about 10 min |
| Indmar inboard (2005 operator's manual) | Only with a flushing device from an Indmar dealer | Otherwise "do not run the engine unless the boat is in water" |
Sterndrives
A sterndrive takes its water through pickups on the drive, so on a lift it behaves like an outboard. MerCruiser's 4.3 MPI procedure removes the propeller, uses the throttle-only button to hold 1,300 RPM, and runs "with sterndrive in neutral for about 10 minutes or until discharge water is clear" while you watch the temperature gauge. Its ceiling: "Do not operate the engine above 1400 RPM out of the water and without sufficient cooling water supply."
Dual water pickup drives need MerCruiser's seal kit as well as the attachment. Some boats also take water through the hull or transom: MerCruiser says Bravo models with closed cooling "must be equipped with a through-hull or through-transom pickup," and that "flushing the engine with the boat in the water can cause seawater to flow into the engine," so the seacock gets closed first. A boat lowered partway into the lake counts as in the water. When the sterndrive is done, it goes back to full down for storage, for the bellows reason covered in outboard up or down on a boat lift.
Inboard wake boats: the intake is under the hull
A V-drive or direct-drive wake boat has no gearcase for muffs. Its raw water intake is in the hull bottom, so the hull has to be in the water before the pump gets anything. Indmar's 2005 operator's manual, which lists engines for boats including the Malibu LS1 and MasterCraft LQ9, says: "do not start the engine when the boat is out of the water without an engine flushing device available from your Indmar dealer."
That bunk is the lift-specific trap. Indmar's pre-launch checklist carries a warning written for trailers: "Make sure the engine water intake is not blocked by the trailer bunk. Blocked or restricted water flow may damage the engine." A lift cradle has bunks too, set to land on the hull's flat sections, and nothing guarantees the intake falls between them (bunk placement is covered in adjusting bunks for your hull). Lower an inboard boat until it floats clear of the bunks before starting it, and know where your intake is relative to them. Indmar's own trailer instruction is the model: "Back trailer into the water. Make sure the engine water intake is submerged."
For salt or brackish use, Indmar suggests a dealer-installed flushing device "that allows easy connection of a water hose"; with one fitted, its instructions decide whether the engine can run on the lift. Ballast, fins and running gear clearance for these boats are in wake boat lifts.
Never in gear on the lift
Neutral is in every procedure above for a reason. In gear on the lift, the propeller either spins in air (the injury hazard above) or pushes water against a cradle built to hold weight from below, not to stop a hull driving forward. Thrust builds fast: Mercury's manual for its 75 to 115 hp outboards says propeller thrust can exceed the preset pressure limit of the hydraulic tilt circuit at roughly 1,500 to 2,000 RPM, pushing a tilted engine back down. A boat sitting partly on its bunks that is shoved forward, then sideways by the propeller's torque, ends up against the guide posts or the forward cross member.
Nor should the engine run while the lift comes up. EZ Dock's lift guide gets this part right: "Shut the boat off and have everyone exit before raising the lift." Once the cradle takes the hull, the intakes leave the water.
Worked example: testing a rebuilt starter on a boat that lives on the lift
Boat: a 22 ft outboard boat on a lift with the keel 30 in above the water and the plug out. Trimmed down, its drive hangs 13 in below the keel (the Wellcraft 221 figure from outboard up or down), so the skeg is 30 - 13 = 17 in above the water, and the intakes sit higher still.
Option 1, lower it. The keel comes down at least 17 in before the skeg gets wet, and more to cover the intakes: call it 2 to 2.5 ft of travel. Most gear-driven lifts move at about 1 to 4 ft per minute (how fast a boat lift goes up), which works out to roughly 30 seconds to 2.5 minutes down and the same back up. Add the plug in before, plug out after.
Option 2, the hose, if the manual allows it: the boat stays up, but the propeller comes off and goes back on. On a 115 hp FourStroke only option 1 exists. Either way, no steady tell-tale within seconds means the key goes off.
Where this answer stops applying
- Your engine's manual says something different. Follow it; this page applies the Mercury, Yamaha, MerCruiser and Indmar instructions quoted here.
- Personal watercraft have their own flush fittings and procedures in the owner's manual; see PWC lifts.
- Winter storage runs need water the same way: before running ten minutes on stabilized fuel, Mercury's storage section says to "Place the outboard in water or connect flushing attachment." The lift's own end of season is in winterizing a boat lift.
- Lifts under a roof. Running an engine inside a boathouse is a carbon monoxide question as well as a cooling one; see boathouse lifts.
Frequently asked questions
Can I start my boat on the lift for a few seconds?
Not with the water intakes out of the water. Yamaha's manual says never to run the engine "even momentarily" without cooling water, and Indmar explains that the raw water pump uses the water it pumps to lubricate its impeller. No engine maker gives a safe dry time. Lower the lift until the intakes are submerged, or use the flush attachment your manual approves.
Can I run my outboard on muffs while the boat is on the lift?
If the manual describes running on a flushing attachment, yes: propeller removed, water on before starting, neutral, idle or low speed, and a steady tell-tale. Mercury's 8/9.9 hp and Yamaha's 60F manuals describe this. Mercury's 75 to 115 hp FourStroke manual flushes through a cowl connector with the engine turned off and gives no running method, so those engines run only in the water.
How far do I lower the lift to run the engine?
Until the cooling water intakes are fully under water. On an outboard, use the water level Yamaha gives for test tanks, above the anti-cavitation plate. On an inboard wake boat the intake is in the hull bottom and can be blocked by a bunk, so lower until the boat floats free of the bunks. Put the drain plug in first.
Can I put the boat in gear while it is on the lift?
No. Out of the water, Mercury and MerCruiser warn never to run the boat with a propeller installed, because a spinning propeller can kill. In the water but still on the cradle, propeller thrust pushes the hull against bunks, guide posts and cross members that are not built to stop it. Keep the engine in neutral until the boat floats free and you are ready to back out.
Sources and further reading
- Mercury Marine, 8/9.9 FourStroke Operation, Maintenance and Installation Manual (1F10201BK): Starting the Engine, Remote Control Models (water pump indicator, p. 76); Flushing the Cooling System and Propeller Replacement (pp. 88 to 89); Storage Preparation (p. 106) (https://www.manualslib.com/manual/3473244/Mercury-1f10201bk.html?page=88)
- Mercury Marine, 75/80/90/100/115/115 Pro XS FourStroke Operation, Maintenance and Installation Manual, 8M0125338 (2016): Flushing the Cooling System (engine turned off, about 15 minutes); Starting the Engine; tilt range and tilt circuit thrust limit (http://download.brunswick-marine.com/filereader/file/pdf/4/enen/outboard/2017/4-stroke/8m0125338r.pdf)
- Mercury MerCruiser, Sterndrive 4.3 MPI operation manual: Flushing the Power Package, Flushing Attachments, Sterndrive Water Pickups and flushing procedure (pp. 113 to 115) (https://www.manualslib.com/manual/1139630/Mercruiser-Sterndrive-4-3-Mpi.html?page=115)
- Yamaha Motor, 60F owner's manual: Warming up engine, cooling-water pilot hole (p. 94); Flushing cooling system with a water tank and with the flushing attachment (pp. 126 to 128) (https://manualslib.mx/manual/83843/Yamaha-60F.html?page=128)
- Indmar Marine Engines, 2005 Operator's Manual (OM0502-04): pre-launch checklist (intake blocked by trailer bunk; intake submerged), Engine Cooling (raw water pump lubricated by the water it pumps), Raw Water Cooling Systems, carbon monoxide danger (https://bakesonline.com/cdn/shop/files/Indmar_2005manual.pdf)
- Hewitt, "Learn How To Use A Boat Lift Properly," March 24, 2025 (https://www.hewittrad.com/about-us/news-and-events/learn-how-to-use-a-boat-lift-properly)
- Hank Johnston, "Manuals provide flushing directions," Louisiana Sportsman, April 30, 2009 (Yamaha F250, Honda BF135A/BF150A, Suzuki DF200 to DF250 flush port instructions) (https://www.louisianasportsman.com/?p=35751)
- EZ Dock, "How to Use a Boat Lift" (https://www.ez-dock.com/blog/how-to-use-a-boat-lift/)
- Moomba owners' forum, "Running the Engine Out of the Water" (owner claims of a safe dry time and impeller failures) (https://forum.moomba.com/archive/index.php/t-12287.html)