
So, your outboard won’t start. What are the likely causes? What should you check first? Second? Third?
It doesn’t matter what brand of outboard you have or whether it’s 2-stroke or 4-stroke. 95% of starting problems are caused by the same group of things and don’t require a mechanic. In fact, only one of the things to check even requires a tool (and that is just a small flat-blade screwdriver); that screwdriver and a roll of tape (I like Rescue Tape — read about it here) are all you need for any of the simple solutions and jury-rigs presented here.
FOUR CLUES TO WHY THE OUTBOARD WON’T START
Start by noticing important clues as to the cause:
- Sometimes the motor will sound like it’s not even really trying to start; other times it’ll sound like it’s almost starting.
- Is there an external tank connected by a fuel hose?
- Do you smell gas? (If so, immediately extinguish any cigarettes or other smoking materials! Actually, extinguish them before doing any of the fuel system checks.)
- Does it start okay, then die when you put it into gear?
Admittedly, there are going to be times when there is no simple fix. If you’re a mechanic-type and know outboards, great. If not, find someone who is. BUT — and this is the important part — the vast majority of problems do not require any special knowledge to find and fix at least well enough to get home.
THE FIRST THING TO DO WHEN THE OUTBOARD WON’T START
If you’re not tied on to your boat or a dock or anchored, the first priority is to not get swept away from safety. Row or paddle back and tie on or drop your dinghy anchor.
And as a side note, always have your basic safety gear in the boat — see my article on Things to Carry in the Dinghy.
WHAT TO CHECK WHEN THE OUTBOARD DOESN’T SOUND LIKE IT WANTS TO START
Four(or five with an electric start) things to check when the motor doesn’t even sound like it wants to start, regardless of whether it has an internal or external tank:
Kill Switch
Make sure that the kill cord (aka “deadman”) is attached properly to the motor. Don’t just look at it — generally, if it’s even a tiny bit out of place, it will stop the engine — or prevent it from starting. I will undo it, and then put it back into place. In my experience, this is the most common cause of failure to start! NOTE: Always wear the kill cord — read more here about why and an easy way to do it if you need your hands free.
Out of Gas?
Check that there is gas in the tank. This is very common if you’re using an in-motor tank (these are generally only seen on outboards up to about 6 HP). They’re small!
Tank Switch
If your motor has both an in-motor gas tank and an external tank, there will be a switch to choose which tank the motor is using (it’s usually on the front of the motor). Make sure it’s set to the correct one! It can easily get bumped to the wrong position when the motor is removed or put back on the dinghy, or when the motor is tilted up and down.
In Neutral?
Many outboards won’t start in gear and it’s easy to accidentally knock the gear shift into forward or reverse. Make sure you’re in neutral!
Battery
If you have an electric-start motor, it may be that the battery is low or dead. If it’s a small HP (20 or under, possibly larger), it probably has a pull start as well and you can start it that way. As a teenager, I pull-started a 50 HP, and I’ve seen athletic men who could pull-start an 85. For most of us, the upper limit of pull-starting is more like 20 or 30 HP. Even if you’re not strong enough to pull-start yours, a passer-by might be so it’s a good thing to know where the emergency cord is and what the procedure is.
WHEN THE OUTBOARD ALMOST STARTS, THEN DOESN’T
Two things to check when the motor sounds like it’s almost starting:
Choke
Try to start it both with and without using the choke, regardless of what the standard starting procedure is. I find this will often start it when the motor sounds like it’s almost — but not quite — starting.
Throttle
Try varying the throttle position a little. Sometimes giving it a little more or less gas will help — I don’t know why, but it’s been the case with every outboard I’ve ever used.
OUTBOARD WON’T START WHEN USING AN EXTERNAL GAS TANK
If your outboard has an external gas tank, there can be a number of problems between it and the motor. Do a quick visual inspection from the tank to the motor and then run your hand along the fuel hose. Many times, the problem will be very apparent when you do this.
Tank Vent Open
If you are using an external tank, make sure the vent on it is open. If it is not, air cannot flow into the tank to replace the volume of gas as it is used. Eventually, there will be a vacuum and the motor won’t be able to suck gas from the tank. If the vent is open but the tank looks “sucked in,” the vent may be clogged (infrequent, but it does happen). Try cracking the gas cap to let air into the tank — if this works, you can probably get to where you are going with the cap cracked (unless it’s a boisterous day when water might get into the tank), then clean the vent.
Fuel Line Connected
The fuel line can come just slightly disconnected at either the tank or motor end. Don’t just look at it; remove the fuel line, reconnect it and then tug gently to make sure it’s fully clipped on at both ends.
Fuel Line Kinked or Pinched
Just like with a garden hose, a kink or pinch in the line will stop the flow of gas. Check that the fuel line isn’t kinked or under something that could partially block the flow. Common culprits are the hose going under the tank, getting pinched between a corner of the tank and the hull, someone stepping on the hose or placing something on it.
Also, check where the fuel line attaches to the motor — we once had an outboard where the fuel hose had been bent almost 90° downward coming off the hose barb, basically crimping it (I have no idea how it happened, probably in loading something large into the dinghy). I was able to hand-hold the hose straight to get back to the boat, then could cut the crimped section off and re-attach the end.
Squeeze Bulb
Squeeze the bulb in the fuel hose to get fuel up to the motor. Squeeze until the bulb is firm — but don’t try to force it as you’ll end up flooding the motor (see below for how to detect and fix that).
If you have just replaced the fuel hose or bulb, double-check that the arrow on the bulb points from the tank to the motor (it has one-way valves in it). If you squeeze and the bulb stays “squeezed” or is slow to regain its shape, check that the tank vent is open; if it is, you probably have a blockage in the hose or it is kinked.
If you squeeze the bulb and it never gets hard or takes more than 5 or 6 squeezes to get hard, it’s likely that there is a crack/cut/nick in the fuel hose between the tank and the bulb which is pulling in air.
If you squeeze the bulb and smell gas, you almost certainly have a cracked, cut or nicked fuel hose between the bulb and the motor, or the fuel line is not securely connected to the motor.
Cracked, Cut or Nicked Fuel Hose OR Loose Connections
See the “squeeze bulb” section immediately above. If the leak is on the pressure side (between the bulb and the motor), you’ll usually be able to see where the fuel is leaking. If it’s before the bulb, you simply have to look and feel to find the imperfection. And note that it may be a hose clamp that has come loose, or it’s possible for the squeeze bulb to have a crack in it (sunlight takes a toll on both the hose and bulb).
If it’s a loose connection and you have a screwdriver, you can tighten it. If it’s a crack or nick, a few wraps of tape will often hold the hose together enough to get back to the big boat (or ashore if you need to buy hose — but you do keep spare hose aboard, don’t you?) IF you keep your speed slow so that you’re not demanding too much fuel.
Of course, replace the fuel hose ASAP — if it is cracked, even just near an end, just cutting off that section is not a long-term fix as cracks are a symptom of UV damage and the whole hose is suspect once you’ve found one crack.
Blocked Fuel Hose
Many fuel hoses have a liner, which can delaminate and more or less wad up (see my post about this). Check for this by removing the fuel hose at the motor. Use a small flat-blade screwdriver to depress the ball valve in the fitting on the hose end, holding the hose end over your bailing bucket or something else that will catch any fuel. Fuel usually will squirt out immediately. Pump the squeeze bulb a few times (since my hands are holding the fuel hose and screwdriver, I use my foot if there’s no one else in the dinghy) and see if there is good fuel flow with each squeeze.
If it seems like there is a blockage, the long-term solution is to replace the hose. As a get-home measure, keep your speed low (so as to need less fuel) and keep pumping the bulb to help force fuel through the blockage. This will work for a brief stint but once the delamination starts, it quickly gets worse. Replace the hose ASAP!
HOW TO TELL IF THE OUTBOARD IS FLOODED
Flooded refers to flooding the motor with fuel, not having dropped it in the water (that takes a totally different and much more “mechanic”-type solution – see here).
If you try starting the motor and smell gas, the motor is likely flooded (yes, as noted above, the gas smell can come from a cracked fuel line, but that is not as likely). Do NOT use the squeeze bulb – that will further flood the motor!
You have two choices for a fix:
- Wait about 10 minutes and try starting again.
- Do not use the choke, open the throttle all the way and try starting again — it will usually take at least 2 to 3 pulls. If it doesn’t start with a half dozen pulls, wait 10 minutes and try again.
Sometimes, after flooding, it will start and then die. If that happens, particularly if it was a cold start, you can now start it using your typical “cold start” procedure with choking it, etc.
OUTBOARD STARTS BUT DIES WHEN YOU PUT IT INTO GEAR
Starting then dying when you put the motor in gear is the classic symptom of having something caught around the propeller — usually a line of some sort, although I’ve found other things as well. Leave the motor off and tilt it up to check, then remove whatever you find. Make sure to get it all!
CONCLUSION
If the motor won’t start, don’t just keep pulling and pulling or wearing the battery down. Systematically think about what the problem is most likely to be and check those items first. Seriously, the vast majority of outboard problems are things that are pretty simple to overcome.
Quickly find anchorages, services, bridges, and more with our topic-focused, easy-to-use waterproof guides. Covering the ICW, Bahamas, Florida, and Chesapeake.
Explore All Guides

Carolyn Shearlock has lived aboard full-time for 17 years, splitting her time between a Tayana 37 monohull and a Gemini 105 catamaran. She’s cruised over 14,000 miles, from Pacific Mexico and Central America to Florida and the Bahamas, gaining firsthand experience with the joys and challenges of life on the water.
Through The Boat Galley, Carolyn has helped thousands of people explore, prepare for, and enjoy life afloat. She shares her expertise as an instructor at Cruisers University, in leading boating publications, and through her bestselling book, The Boat Galley Cookbook. She is passionate about helping others embark on their liveaboard journey—making life on the water simpler, safer, and more enjoyable.
Ernie Lorimer says
My Yamaha 9.9s typically need the throttle to be goosed a few times for a cold start. They have an accelerator pump at the bottom of the carb that sprays a little gas into the throat when the throttle is advanced, to help it come up to speed before there is enough air flow to draw gas at higher rpms.
Goosing it a few times sprays some gas into the throat that helps it start, and it is necessary almost all the time.
Bruce Stewart says
Excellent article Caroline. Thanks.
Captain Mark Nine Lives says
“Flooded refers to flooding the motor with fuel, not having dropped it in the water (that takes a totally different and much more “mechanic”-type solution).”
Actually all you need is to be prepared because at some point you will do this. The secret to rescuing your motor is speed and following a couple of simple steps. Get the motor out of the water and quickly follow these steps.
1. Remove the spark plug
2. Pull the starter rope through until all the water has been pumped out of the cylinder.
3. Spray a ton of WD40 or the like into the spark plug hole.
4. Pull the starter rope through several times.
5. Spray a lot of WD40 in again and quickly put the spark plug back in and connect the spark plug wire.
6. Start the engine and run it for a while.
I’ve never had this fail to work and never had any engine issues after,
Carolyn Shearlock says
When it’s gone into salt water, the motor has to be flushed with considerable amounts of fresh water, too. For a 4-stroke, several oil changes. If the gas tank went in the water, get fresh gas before even trying to start it as the gas will have water in it.
Another key is not pulling it out of the water until you have all the tools assembled. Once you get it out of the water, work quickly. It’s usually best to replace the spark plug, particularly in salt water.
And as I said, doing this requires a certain amount of “mechanic-y” skills, which was outside the scope of a 101 article. But yes, good to know how to do.
Rod says
If its flooded with salty , its best to soak it in fresh and agitate it. The salt residue is the cause of damage and will reappear later even months. Corrosion will eat away at electrcal items and connections. Remove flywheel, if you can and wash out electrics and dry.
Gary says
Kill switch can fail, you can disconnet it, and motor will start. Use this trick if you forget the laynard. A good reason to lock your dink
Carolyn Shearlock says
Yes, you can disconnect it if you know what you’re doing. A bit beyond the scope of this post, which is simple things to check.
Craig Newton says
Love your articles Carolyn.
Carolyn Shearlock says
Thank you!
Rob says
I have a 1988 45hp Mariner engine runs with the ear muffs on but as soon as the boat gets put I to water it won’t start. Take it out crank it with the muffs on it starts after a couple cranks. Carbs have been done fuel pump duel lines stater and foils new plugs and wires. Compression is good . Only won’t start when the lower section of motor is in the water. Very frustrated any hell would be appreciated,
Carolyn Shearlock says
Boy, I’m not a mechanic and don’t have an answer for you. One thought is whether there is something with the cooling water circuit, since that seems to be the difference.
Jason says
Did you ever find out what the problem was? Mine is doing same thing
Sammy says
I just had same issue with my 87 evinrude , beat me down for 2 months finally took to a mechanic and it was a $6 piece ,a sheared fly wheel key I’d try that . Granted the flywheel puller is a little pricey but it’s worth a shot
Goldie says
Rob, did you find the problem, because my has the same problem. I have a 50 Tohatsu and it’s got same problem. It’s not overheating it just want crank when you launch t. But with ear muffs on land it will crank and run great.
Garry says
Most outboard vent the exhaust below waterline it be restricted.
Jim says
I have a force forty outboard engine. It starts sometimes and then dies after about 5 minutes. Try to start will not work.
Carolyn Shearlock says
Hi Jim! If the simple solutions listed here don’t help, you probably need to talk to a mechanic.
Carla says
Great article Caroline. One other thing to check in the top four. Many outboards will not start in gear. Don’t ask how I know, I wouldn’t want to embarrass someone. Just check to make sure it’s in neutral and try again.
Carolyn Shearlock says
Another good point! Don’t know how I missed including that. I’m going to add it now.
Hugo Sanchez says
Hi Carolyn – Hope all is well! I have a 88 Bayliner Capri that will only start with the choke button being pressed and held there. What do you think is my problem? I just bought the boat and the first two times I took it out everything worked like a charm. But now, it will only start with the choke button being held in. Do you have any recommendations as to what the problem is?
Thank you so much!
Carolyn Shearlock says
First thing to try would be cleaning the carb, particularly if it only runs if you continue to press the choke. Sometimes you have to clean the carb a couple of times before it’s sufficiently clean. If that does not do the trick, it’s time to call in a mechanic.
Dean says
i have a f25elh mercury four stroke it will run fine and get you as far as you want to go but when you shut it off it will not start back up. Then when you get home it will fire right up and run fine.
Carolyn Shearlock says
That’s beyond the scope of this article. You’ll want to research carburetor troubleshooting.
William Serdynski says
Four stroke engines that start up when cold but won’t when hot usually have valve problems. As the engine warms up, the valves expand and don’t seat as well causing a loss of compression. As long as the engine is running, it usually keeps running. When it cools down, it will start again. A valve job is needed. You will be amazed how quickly engines start with a fresh valve job.
Ken Humphries says
I have a Mercury 2016 60hp 4 stroke motor. It started up and ran just fine until the foot of the engine hit a stump going pretty slow but it knocked the engine off and couldn’t start it up again, it wouldn’t even turn over. Could that bump cause a safety switch to stop engine or cause the timing to get knocked out of line? Help!
Carolyn Shearlock says
That’s going to require more of a mechanic. Good luck!
Ken Humphries says
Thank you, I was afraid of that.
Duncan says
I have a 2001 tracker targa with an internal fuel tank. My issue is, I hook up my 60hp Mercury to an external tank runs like a champ. Soon as I plug it into the internal tank. Won’t turn over. I have a new supply fuel line, checked tightness and sprayed for leaks no problem. Took the fuel siphon valve and fuel withdrawal stem out perfect no blockage. Brand new non ethanol gas with appropriate sea foam additive into it. It is roughly a 20 gallon tank.
I had the boat running at 3000 rpms like two weeks ago.
Carolyn Shearlock says
My first thought is that air is getting into the fuel line (cracked line, fitting or pickup) on the internal tank to motor. A crack that lets air in won’t show as a leak on the suction side.
Rod says
The engine may be too low in water creating back pressure through exhaust
Other thing you may try is to remove plugs taking care with fuel and crank over to see if you’re getting water ingesting to cylinder you may see moisture on plugs or head. Depending on age of engine
Paul St-onge says
40hp mercury Efi starts and stops right away then won’t start for about 10 minute
David Rosenbaum says
I have a new 6hp 4-stroke Tohatsu that I started today for the first time. ( Started on the 2nd pull )After letting it idle for 12 minutes, I shut it off.
After a couple of hours I tried to to start it again and nothing: doesn’t start or even sound like it might. Ideas?
( Prior to the first start, I followed the manual: added oil and pulled starter cable a few times with lanyard detached to circulate oil prior to starting; added fuel to internal tank [non-ethanol with StaBil 360], left vent on cap ‘open’, replaced safety lanyard; motor on outboard stand and 30-gal rubbish bin filled with water to 4” above anti-cavitation plate. Started on second pull; idled smoothly. I also shifted to fwd for a minute or two, then back to neutral. After 10 mins, I stopped it by pressing kill switch.)
Carolyn Shearlock says
Most likely the kill cord got slightly out of place. Remove it and reinstall it, then try again.
David R says
Dear Carolyn,
Thank-you for your suggestion. (And I’m happy to have discovered TheBoatGalley! )
One of the service people where I bought it, Cumberland Watersports (Online Outboards), said that it was likely overfilled with oil (!) and suggested that I drain it and refill with 12-13 oz even though it would read a bit low on the dipstick. I did that and it started right up! So a little Tohatsu peculiarity…
Micheal hill says
I have a 35 hp mercury. I hit a stump and now all it will do is pop and try to run, but will not start. It acts like it’s out of time. But shear key is good. Can anyone help me?
Todd Chiusano says
I have an 07 Honda 90 . It will not start unless I shift from forward to reverse a few times first. Are there contacts somewhere I can check or clean? Or could it be something else ?