2005 15hp Honda OB


New member
Runs for 15 seconds and dies. Acts like the spark is dying.

Last season replaced computer, carb/gaskets, plugs, impeller...ran great at end of season. Went to start after 6 months sitting and wont stay started.
How did you prep it for that "long term" storage? Run it until it stops then open the carb drain screw for 30 seconds?

If not, then that might be the reason for what it's doing now.

But there are other things it could be.

Check your fuel tank vent is open and not clogged. You can also try leaving the fuel cap off the tank to see if there's an improvement.

Have you drained the liquid from the fuel chamber? That's the black rubber cylinder mounted on the oil dipstick tube.

Sometimes in storage critters crawl in and make nests or chew on things....especially wiring and hoses. Inspect for that. Especially if this is an electric start model.

Just some ideas.

Hope you get it sorted out.
Didn't do anything special since we are in San Diego...just left it on the davits under canvas. The fuel is good and the tank vent is open.

It starts instantly and runs great for 10-15 seconds and before I can give it throttle it starts running on one cylinder and sputters till it dies. If I start it more than a couple times it floods and requires sitting for 5 minutes before I try again.
Well, these carbs are fairly famous for being finicky, easy to clog and hard to clean. Not ensuring the float chamber is completely empty before storing is inviting problems.

You might try opening the float chamber drain screw, releasing the fuel and then spraying carb cleaner into the float chamber.
It's easier to do if you remove the drain tube from the plastic nozzle on the side cover. Do that a few times then finish by spraying WD-40 up there and close the drain screw to let it sit a while. That will sometimes free up a stuck float.

Have you tried pumping the primer bulb and opening the throttle half way (might need a helper to do that) as it dies? If not, try doing that first to see what happens.

If no joy there then pull the spark plugs and have a look.
I would probably just try a new set anyway. Look closely at the metal rings that attach the wires to the plug tips for damage or signs of corrosion.

Before putting the plug wires back on smear a very thin coating of dielectric (tune-up) grease on the inside of the boot to seal out moisture.

All in all though, this still sounds like a fuel starvation issue and might involve sediments in the bottom of the float chamber from the leftover fuel in there.

It could be a cold start enrichment problem with either the "manual choke" for pull only or the SE valve for electric.
But I would need to know which it has before telling you what to look for there.

Good luck.
It's got a brand new carb installed...only has a couple weeks of use at Catalina Island last season.

I was thinking it seems like a SE valve issue as well. Not sure what the best way to check that would be?
This is the advice JGMO gave me regarding testing the SE unit and he really knows his Hondas!!

The pintle pin or "needle" should extend when 12 volts are applied for more than 1 to 1 1/2 minutes.
The enrichment is defaulted to FULL RICH at start up. After start up the enrichment electrical coil under the flywheel delivers the volts to heat the element that moves the pintle. The pintle pin extends and closes the enrichment reservoir feed to lean out the mixture.

When testing the SE valve, apply 12 volts for 2 minutes or more and look for the pin to extend...about 1/8" to 3/16" if I remember correctly.

The SE valve rarely fails. Typically, it will fail with the pintle fully retracted. The resulting symptom is an engine that starts easily when cold but then runs too rich and dies when warm.

However, it is possible for the pintle to "stick" in the fully extended position and shut off the start enrichment orifice and causing hard/no cold start.
You stated it perfectly!
But that's only if it is an electric start model.

If it's pull start only, it doesn't have the "thermo valve".

They both have "se circuits" (no conventional "butterfly" choke) but the pull start se valve is hand operated by cable, much like a butterfly choke.
Thanks but I simply copied and pasted your bit from a previous post. The OP did say his motor had a new carb (mine came with the SE valve so technically his SE valve (if electric start) will also be new. His problem almost sounds like he fills the float chamber up and the motor starts perfectly but dies after 15 seconds .. could it be that no fuel is reaching the float chamber once the motor is running ?? My BF20D is running like a dream thanks to you.
Well, my fear for this one is that they left the float chamber full of fuel and then parked it for 6 months.

It is my opinion that the SE feed conduit at the bottom of the float chamber is likely plugged badly enough that there's almost no flow to keep the SE "well" supplied enough to keep the engine running when cold.

It could also have a "sticky" float due to what the stale fuel has done in there.

It's why I preach about not letting one sit more than a couple of weeks with fuel still in the carb.

On the other hand, if their fuel was properly dosed with Marine Stabil or Marine Techron ll that might not be the case and this could be an SE valve or other issue.
I guess it's tough if you are a long way from the water or if you have icy Winters so there draining the float chamber (and maybe the fuel chamber too) is a good idea although to get the fuel chamber off on my 20 I do need to drop the side cover so I can slide it off the dipstick. My Whaly370 dinghy lives in front of our liveaboard catamaran with the BF20 tilted up so I have no excuse not to give it a quick spin every couple of days. Before I scrapped my old carb I did find that the feed conduit to the SE valve was clear ..it was my primary jet tube that blocked solid sadly. Is it also a good idea to ditch what fuel is left in the outboard tank if you are storing the motor for a long time?
Oh, for sure! These little carbs want fresh, clean fuel only! If you're not going to burn it up pretty quickly, it should go in an active vehicle rather than taking any chances trying to store it.
Just not worth the risk IMO.