(Yamaha) Alarm Signal Question

[Paul From Minnesota]

I'm going to try to explain this the best I can, but I'm a total newbie. Sorry it's a wee bit long.

I have a newly acquired 1988 Yamaha 200 ETLG. It has worked fine for about 2 months, no problems.

However the last two times I've had the boat out, I get an alarm after I've been idling or moving at very low speed for 2 minutes or so. When I tried to accelerate (thinking that perhaps it was needing more water), the engine ran very rough, almost as if it was not on all 6 cylinders, and I had very little power or acceleration, as if the lower unit was not receiving full power.

The first time this happened, it just suddenly stopped malfunctioning all on its own - the alarm stopped and the engine began running normally all at once.

The second time this happened, on a whim, I put the engine in reverse, and the alarm stopped immediately, and when I put it back in forward gear, the alarm and the rough-running were both gone - everything back to normal again.

Water intake is clear, and both oil tanks are full.

I don't know what is triggering the alarm, what is causing the rough-running and power-loss, or why putting it into reverse and back into forward drive made the problem stop.

Any help?

 

[Silvertip]

Re: (Yamaha) Alarm Signal Question

You are experiencing an overheat condition at idle which is very likely due to a malfunctioning thermostat or a weak water pump. You need to understand that just because the tell tale shows a good stream, that does not mean the engine is cooling properly. An engine that overheats at idle is generally due to the thermostat being stuck shut or nonfunctional. An engine that overheats at speed is generally due to a stuck or malfunctioning bypass valve. During an overheat the electronics goes into a limp-home mode which limits the engine rpm which is why the engine runs rough. Fix this problem immediately or you will be looking for a new engine or rebuilding this one.

 

[Paul From Minnesota]

Re: (Yamaha) Alarm Signal Question

You are experiencing an overheat condition at idle which is very likely due to a malfunctioning thermostat or a weak water pump. You need to understand that just because the tell tale shows a good stream, that does not mean the engine is cooling properly. An engine that overheats at idle is generally due to the thermostat being stuck shut or nonfunctional. An engine that overheats at speed is generally due to a stuck or malfunctioning bypass valve. During an overheat the electronics goes into a limp-home mode which limits the engine rpm which is why the engine runs rough. Fix this problem immediately or you will be looking for a new engine or rebuilding this one.

I had a trusted marine tech take a look today - he said the whole impeller assembly is shot. Does this sound like the answer to you, or do we need to dig further into it? Should I have him replace the thermostat anyway just to be safe?

 

[erniefish]

Re: (Yamaha) Alarm Signal Question

to be safe i would do thermostat as well ,also clean the poppit valve,that way every base has been covered,good luck