Yamaha 25 4stroke losing power

Joined
Mar 28, 2013
Messages
18
First day out today. Outboard went well for ten minutes then lost power but still ran. returned to dock. Stalled when throttle was reduced. When started again out of gear seemed to rev ok although a bit smoky. Still stalls if run on slow idle. Has anyone any idea what is wrong with it. Should I risk trying it on the water again.
 

astuckey

Petty Officer 3rd Class
Joined
Sep 4, 2011
Messages
83
Re: Yamaha 25 4stroke losing power

Hi there,
Sounds like you might have bad gas or water in the fuel. Have you checked your fuel system? I would start there.
 
Joined
Mar 28, 2013
Messages
18
Re: Yamaha 25 4stroke losing power

Tried outboard again. Seems to start ok and run ok. However still quite a bit of smoke. Does this indicate a problem.
 
Joined
May 10, 2013
Messages
6
Re: Yamaha 25 4stroke losing power

quite a bit of smoke you say,does it clear or continue to smoke? what color is the smoke?
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: Yamaha 25 4stroke losing power

have you checked the oil level?
Could be getting fuel into oil and overfilling.
It would also hurt motor if oil is contaminated
A 4 stroke should not be burning oil and smoking
 
Joined
Mar 28, 2013
Messages
18
Re: Yamaha 25 4stroke losing power

May have over filled oil as I have changed it just before launch, along with plugs and impeller. Will check it in the morning. If I have do Imneed to drain all oil and refill or just remove some. Will look at colour of smoke at the same time. as for quantity not sure how to quantify this. Maybe a wee bit less than a good bit. Only joking. About a quarter square metre at a time. Comes from exhaust from beneath water so is not steam.
 
Joined
Mar 28, 2013
Messages
18
Re: Yamaha 25 4stroke losing power

Smoke is white. Coming from top exhaust now. Took boat for another run. Went well for 5 minutes then lost power again. Should I just get a new outboard.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: Yamaha 25 4stroke losing power

take to Yamaha shop and have them check it out to see what is happening.
sounds like it is overheating, but hard to tell from what you write
 
Joined
May 10, 2013
Messages
6
Re: Yamaha 25 4stroke losing power

It sounds like your motor is burning oil, this means there could be damaged rings letting oil past or perhaps the way you store your outboard when not in use. If you store the motor in a negative trim the oil that sits behind the piston can slowly seep to the front causing it to burn when you start your engine the next time... WHITE SMOKE always means its burning oil on ANY car or boat engine.... Car pistons face upwards so unless there is a crack in the block allowing oil to pass in front of a piston to burn..Outboard pistons are Horizontal so trimming your motor up when not in use drains the oil back down to the pan :)
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: Yamaha 25 4stroke losing power

blue smoke is oil, white is water, and black is too much fuel
 
Joined
Mar 28, 2013
Messages
18
Re: Yamaha 25 4stroke losing power

Showed it to mechanic today. He thinks it is steam and might be a thermostat problem. He is going to look at it next week. I will update you then. Thanks for your replies.
 
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