yamaha outboard

[alan mitchell]

My outboard engine dosent give me the boat speed I had last year.The engine starts ok and runs well too but with full throttle the boat is slow.Can you give me any possible causes for the problem

 

[rodbolt]

Re: yamaha outboard

can ya tell us a year and HP. also what is the max RPM now.

 

[alan mitchell]

Re: yamaha outboard

Originally posted by rodbolt:<br /> can ya tell us a year and HP. also what is the max RPM now.

The year of the outboard I am not sure but I believe its about 8 years old and is a 50cc.Its fitted to a shetland sheltie.On the rev counter on the dash the max revs is about 28000.All was ok and the boat was quite fast until a few weeks agao and althought i cant quite remember the revs then,I think it was about 46000

 

[bossee]

Re: yamaha outboard

Hi,<br />So a Yamaha 50 hp 2-stroke about 1997 or so is what You have.<br /><br />The tachometer:<br />So you only get 2800 RPM (revolutions per minute) today?<br />But it was 4600 RPM before it seems.<br /><br />Your outboard should probably at full throttle have about 5500 RPM. So You are little low on RPM if 4600 was your max RPM at WOT (wide open throttle) before. But that is another problem (probably solved with a prop with 2-3 inch lower pitch).<br /><br />Personally I would first make sure I had sparks on all spark plugs.<br />Then make sure it runs on all cylinders (it has 3).<br />Then I would make sure I had proper fuel delivery (from tank trough bulb and lines trough fuel filter and last to the fuelpump and trough the carburators.<br /><br />Any alarms going on? Overheat alarm?<br />Not sure at what RPM the rev limiter kicks in but it would probably be something between 2000-3000 RPM.<br /><br />When was this outboard last serviced?<br />Has the impeller (rubber water pump wheel) been changed in last 2-3 years?

 

[alan mitchell]

Re: yamaha outboard

Thanks for the info I will try your suggestions this weekend.Thanks again