Yamaha 115, 2 stroke in trouble - The Hull Truth

mrossj1 · 11-20-2009, 09:17 AM

Last week I was returning to port at 3/4 to WFO when I heard a loud "bang" and thought something hit my motor cowling. I entered the no wake zone soon after and idled to the dock without any problems.

This morning I put the boat in the water, she started up no problem, idled like always and then cruised through the no wake zone without any problems. Once I put the hammer down to get up on plane is when I experienced my problems.

The motor didn't get the boat on plane and then started sputtering, lost power and almost died. I put it in neutral and it idled fine so I tried it again and the motor sputtered and then died. Each time I could start it up and let it idle without a problem. I was able to make it back to the dock at idle speed without any problem.

I thought it might be fouled plugs due to the amount of trolling I had done the week before so I changed the plugs. The plugs that were removed were all consistant with each other (black but not gooped up with oil, remember this is a 2 stroke).

I changed the plugs, splashed the boat again, she started without any issues, idled like before and did the exact same thing.

Please help.

Diverboy · 11-20-2009, 09:25 AM

I'm no mechanic, but what you described would lead me to believe you have a lower unit problem. When at idle, have you tried to slowly give it gas instead of putting the hammer down? When in neutral, will it rev up quickly and be crisp without sputtering? If so, sounds like a gearing problem that presents itself when put under a load.

top1000nole · 11-20-2009, 10:14 AM

fuel pump

Diverboy · 11-20-2009, 10:50 AM

Fuel pump does sound logical, but what would account for the loud bang?

mrossj1 · 11-20-2009, 01:27 PM

Where is the fuel pump located?

mrossj1 · 11-20-2009, 08:11 PM

anyone?

wetneck · 11-21-2009, 08:13 AM

your fuel pump should be mounted on the port side of motor, just follow the hose after the filter. unbolt it rom block, pump ball and if fuel comes out of vac port in rear it is bad... but that wont explain a loud knock.

1bayouboy · 11-21-2009, 01:09 PM

Sounds like a fuel delivery issue to me.....
The fuel pump has a diaphram pumped by pulses from the crankcase....if the rubber diaphram gets a hole or tear in it then gas can get into the crankcase and it loses efficiency.

mrossj1 · 11-21-2009, 04:13 PM

Thank you for all your input on my question. We have found the culprit, dirty fuel filter and some water. I cleaned the fuel filter and installed a fuel water seperater and the boat ran like a champ today. Again, thank you very much!!

triumphrick · 11-21-2009, 04:53 PM

Quote:

Originally Posted by mrossj1

Thank you for all your input on my question. We have found the culprit, dirty fuel filter and some water. I cleaned the fuel filter and installed a fuel water seperater and the boat ran like a champ today. Again, thank you very much!!

Yet another satisfied customer.....