99 15 hp 4 stroke wont stay running

[bama113]

today i got a good deal on a yamaha 15 hp 4 stroke. The motor had supposedly been used a handful of times and hadn't been run in a couple of years. It had some cosmetic damage from falling off a sailboat at the boat ramp. The compression was good so i bought it for $300 without seeing it run. I got it home and it fired up on the second pull. It ran great for 5 minutes at idle on a water hose connection. It pumped a strong stream of water the whole time. At the 5 minute mark it abruptly shut off....almost like someone hit the kill switch. The next few times it would run normal and then sputter to a stop after 10-20 seconds. Now it runs for a couple of seconds then shuts down. The oil level is good...no warning light. Brand new fuel line with new fuel tank. Made sure the tank was venting.

Where should I start in diagnosing the problem?

 

[railroad.builder]

Re: 99 15 hp 4 stroke wont stay running

be carefull running engine hooked up to the hose connection - use muffs. you can get yam owners manual on thier usa web site it says to use muffs when running engine hose connect to flush engine - sounds like the motor got hot

 

[bama113]

Re: 99 15 hp 4 stroke wont stay running

I apologize....i was using muffs. Didn't know the exact term for them

 

[99yam40]

Re: 99 15 hp 4 stroke wont stay running

Sounds like you have some plugging in carb. after sitting that long and then starting something came loose and plugged jet/passage

 

[bama113]

Re: 99 15 hp 4 stroke wont stay running

Went out today and tried to narrow down the problem. The motor is now in a barrel with fresh running water....shouldn't overheat. I noticed that when I put it in gear and give it full throttle (not running) and then start it up again in neutral, it will run for a 1-2 minutes and then shut off. If I don't give it gas before starting it, it will only run for a second then shut off. I'm having trouble getting the fuel lines off the filter....but will check it as soon as I do. Any way to easily check the fuel pump?

There is also this annoying linkage that connects to the throttle linkage. I hit it every time I pull the dipstick. It is connected to a tiny box that sounds like it has small gears or something in it. The tiny wires coming out of it aren't connected to anything. Can I take this linkage out? It seems as though it is preventing the throttle from moving freely and returning back fully to idle