Yamaha 15hp won't start

[Deleted member 478]

Yamaha 15hp won\'t start

At the moment, I am anchored in a bay north of Salvador, Brazil where there are no Yamaha dealers to be found and my outboard has given up the ghost. Not one of the ‘instant expert’ cruisers that are also anchored in the bay have been able to get it going again. So far, we’ve done the following:
• Cleaned the primary & secondary jets – they’re clean.
• Checked that the condom thingies in the vacuum pump are not split
• Checked that there is a spark – it is good.
• Checked that fuel is getting into the cylinders – the plugs are wet and they smell just like 2 stroke fuel
• Changed the fuel and used a filter that removes water from fuel before putting the new fuel into the tank
• Changed the spark plugs for new ones
• There are tiny water droplets on the spark-plugs - not fuel because it does not evaporate
• By the way, the engine has not been submerged – except for tropical rain storms almost every night.

Two things; what else can I do and does anyone have a Yamaha service manual that they can email to me please (I've unsuccessfully searched the net for one)?

Thanks in anticipation.

 

[VicS]

Re: Yamaha 15hp won\'t start

[ QUOTE ]
There are tiny water droplets on the spark-plugs

[/ QUOTE ] Dont like that!

Dry the plugs, make sure there is no water in the fuel system, float chamber? Crank the engine a number of times (spin on starter if electric) with plugs out to expell all water from within.

replace plugs, prime, try again. Try spraying a little fuel mix directly into the carb too.

Worst case scenario is a head gasket gone maybe.

 

[Scillypete]

Re: Yamaha 15hp won\'t start

[ QUOTE ]

• There are tiny water droplets on the spark-plugs - not fuel because it does not evaporate


[/ QUOTE ]

Anyway of telling if its fresh or saltwater? if its salt its serious

 

[pete]

Re: Yamaha 15hp won\'t start

Could be down to bad compression caused by petrol washing the oil of the cylinder bores, remove the plugs squirt a drop or two of oil in each spark plug hole and try again.

good luck
pete

 

[OGITD]

Re: Yamaha 15hp won\'t start

As what VicS has already stated, also I had a very similar problem with a Yamaha detuned 8 now starts on ½ pull every time.

1, Disconnect each electrical connection (one at a time) apply a little WD40 & reconnect, ensuring good connection.
2, If the unit will fire up while pouring / squirting a little petrol directly into the air intake then runs rough for a few seconds & dies it is probably carburetion.
3, Yes clean the Jets manually & I also used a chemical Carb cleaner.
My problem was that I was not getting fuel / enough fuel into the float chamber.
Ensure that the float needle valve moves sufficiently and freely after removal and cleaning. I had to adjust (bend) the tiny support bracket which projects out of the float with a set of fine nosed pliers.
4, Also on the Fuel / Vacuum Pump, ensure that if one of your diaphragms has a small hole (design not fault) the diaphragm is in the correct orientation (easy mistake to make).
But for future peace of mind I have ordered and will be fitting a Carburettor service kit.

Also assuming that you have ruled out bad fuel / fuel mix.

Hope to hear you have it running soon!

OGITD’s

 

[Lakesailor]

Re: Yamaha 15hp won\'t start

If it's a remote tank that is your source of the water. It sits at the bottom of the tank and once the level reaches the fuel outlet pipe it will pull through to the carb.
It's caused by leaving the tank vent open. The tank pulls moist air in at dusk and it condenses out in the tank. Takes quite some time for it to happen, but happen it does. It caught me out on Windermere so a hot but moist place will be worse.
You have to dump the remote tank's fuel (or separate the fuel/water) and start with pure fuel mix after letting the tank dry out.
It can still happen in tanks on the power head, but is less likely.

 

[Deleted member 478]

Re: Yamaha 15hp won\'t start

UPDATE:

One of the piston rings had rusted so badly that it no longer did what it was designed to do. The compression on that cylinder was down by over 30%. The engine is at a Yamaha dealer and we're in serious debate about warranty issues.

At the end of the day, it's still great being a liveaboard and not having to deal with lawnmowers etc