Outboard not starting quickly

[Daveroo]

I have a 115 HP 4 stroke Yamaha about 8-9 years old I think (bought used with boat). Up until recently I never had any problems starting it. Turn the key and it starts within 2 to 3 seconds. But the last couple of times out, I noticed it would not fire up right away. The engine cranked, but it would not fire up. I let it crank for about 8 - 10 seconds and then let it rest for a few seconds. Then it fired up after a second crank of a few seconds. On my last outing, the same thing, except this time just as I stopped cranking the engine gave a big pop and backfired it appeared. I waited a few seconds and cranked again. It eventually fired up and it was no problems for the rest of the day. On both days I headed out fairly late (late morning), so it was fairly warm outside. My boat is garage kept so it is well protected from the elements. Any thoughts what the problem might be?

Daveroo

 

[scott craven]

Have you changed your plugs lately ?

 

[sudsy]

Is this fuel injected or carb?

 

[Rum Buddies]

make sure your choke is still working

 

[MonkeyWrench]

Definitely check the plugs, at very least it will provide an indication that the engine is running equally on each cylinder, but i would expect the problem to be more fuel related. Yamaha's have a pretty bulletproof ignition system and I have to service the carbs quite regularly. Is there a spin on fuel filter on the boat? Did the motor sit for any length of time before you started noticing this issue? Once it gets running, do you have any issue with motor running at idle? Ethanol has created fuel that breaks down so much quicker than it ever did before, fuel sitting in a float bowl for a couple months can solidify and cause running issues.

Also don't forget the simple things, check balls in the primer bulb could be getting weak allowing fuel to drain from the line, a sticky anti-siphon valve in the tank could prevent the motor from drawing fuel.

 

[salmonkiller01]

Try adding a bottle or mercury quick clean to your fuel, the stuff works wonder, I am sure Yamaha has the same stuff, but know many people including myself who swear by quick clean for outboards, cars, lawnmowers....