Engine slow down

[Robbins73]

I'm new to taking care of outboard engines so with that said here's what I had happen. I was out crusing on my Mako 171 and had been running the boat between idle and high running speed for about an hour maybe more. I was heading for an island at high speed when the engine slowed down to just above idle. It would not increase speed. I was afraid to pull the throttle back down to idle until I got close to the dock because I didn't know if the engine would shut down and not start. I was about 2 miles from the dock. The engine never sounded a warning horn and I'm not sure of the engine instruments. I have an all in one, gas, oil, and temp gage but I can't figure out how to read the thing. So any ideas and help would be appreciated. The engine is a 2002 Yamaha 115 2 stroke.

[DennisG01]

Sounds like a fuel issue. There's multiple things to check, but a few of them that come to mind...

-- Vent or vent line restriction - try opening the fuel cap to alleviate the restriction
-- Check fuel pressure when running

If it's the Yamaha gauge, there are icon/indicators to show what particular thing you're looking at when cycling through with the button.

FYI... you should know how to check both the remote mounted oil tank and the main oil tank - you can do that visually. However, they would set an alarm... IF the alarm is working. Check levels.

[Robbins73]

Thanks for responding so quickly. I was just checking my engine out to see if it would idle like it did before I went out. And it doesn't. Its sluggish and shut off a couple of times. I will try opening the fuel fill cap and see what that does but I have no idea how to check fuel pressure. Could you explain. And do you have a suggestion for a manual on this engine. Something that would help with maintenance and repairs. Thanks

[99yam40]

1st thing I would do,would be to make sure the gauges and horn work to tell you there is a problem with oil level and overheat.
RPM reduction and limiting is a back up to let you know the motor has a problem if the horn and/or gauges do not let you know