Outboard Engine Starting Problems

Troublshooting why an Outboard Motor that won't start


troubleshooting an outboard with starting problems.jpg
troubleshooting an outboard with starting problems.jpg
This article describes the most common outboard starting problems and introduces a methodical approach to testing each with simple tools and a basic process.

Grouping Common Starting Problems

Start by understanding the basic elements required for combusion:

  1. The presense of fuel/petrol/gas being delivered in right mix
  2. Compression in the combusion chamber
  3. A source of correctly timed ignition 
  4. The absense of any environment inhibitors, e.g. water ingress

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.

Basic First Checks

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.

will it or wont it

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!


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.


Two things to check when the motor sounds like it’s almost starting:


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.


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.


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.


Missing something or have a comment? Post it below...

Be the first to comment

Leave a Reply

Your email address will not be published.