1992 115 Yamaha going into Limp mode once I go over 4000 rpms, please help

[pmragazzo]

About a month ago I bought a 1992 115HP Yamaha 2 stroke outboard motor. It has been hooked up and seemingly worked ok. But every time I go over 4000 rpms it starts to lose rpms and won?t really go above 2000 rpms again. The oil well in the engine?s float was stuck at the top. I replaced the float and the oil now correctly transfers from the boat oil well to the ?in-engine oil well?. I constantly check the cyclinders to see if they are hot, and they never feel abnormal. The pisser seems to have a constant stream as well. The only problem I can identify is that there are 4 wires that do not have corresponding wires to connect to.
Yellow wire- the yellow wire is connected but there is a spliced wire sticking out with a male connector that is not connected to anything
Yellow w/ red stripe: this wire is coming from the engine and has no wire to connect to
Black wire: when connected to a volt meter testing 12v it shows a high number like 80. It is in the same group with a pink and orange wire. I have attempted to attach it to another negative, but no difference.
Orange wire: inside the engine
I really just want to be able to fish and can?t seem to figure out why my engine is apparently going into ?limp mode??. The boat starts up and seems fine until I push it past 4000 rpms. The oil float works and the manual switch. I have cleaned the carbs best I know how. Any input would be greatly appreciated

 

[Capt Ken]

Re: 1992 115 Yamaha going into Limp mode once I go over 4000 rpms, please help

Replace the diaphrams in your fuel pump.

 

[Bamaman1]

Re: 1992 115 Yamaha going into Limp mode once I go over 4000 rpms, please help

You're hitting the fail safe mode. It often happens because of low oil levels in the big oil tank, or low oil levels in the small oil tank on engine--if the electronics are not working properly to start and stop the oil transfer.

The other half of the oil injection is completely mechanical, and has nothing to do with the electronic part of your engine. It's very reliable.

You can also get a fail safe mode if your engine is overheating. You can check the head temperatures with a laser thermometer to see if both heads are running the same temperature. The thought is that one thermostat will fail before the other.

Have you dropped your lower unit to manually check the condition of your water pump impeller? A bad impeller would make your engine overheat, and go into fail safe mode.

And has been said, check your fuel pump diaphragm. 90/10 wreaks havoc on anything that's rubber, especially fuel pump diaphragms. How is the fuel filter element under your carbs? Are the fuel lines and the siphon end down in your fuel tank clean? Is your gasoline new or has it been in your tank over the winter? Bad spark plugs can cause rough running, and have you changed them recently? Have you recently changed the lower unit lube, and are the lower unit gears and bearings in good condition?

Figuring out problems is often just performing a bunch of small job tasks. 2 strokes are pretty simple machines, and can sometimes be a little frustrating to diagnose problems in.

 

[pmragazzo]

Re: 1992 115 Yamaha going into Limp mode once I go over 4000 rpms, please help

This is what I have tried in the past couple days to fix it.
Put new gas and treatment in the boat
Put in new spark plugs
replaced spark plug wires
removed lower unit oil and replaced (was a lil milky) replaced o-rings
replaced float in the in engine oil well

Ran it again and same problem occured. Thank you for yalls help. I will look into the fuel pump

 

[pmragazzo]

Re: 1992 115 Yamaha going into Limp mode once I go over 4000 rpms, please help

Had a new water pump and thermostats installed. And come to find out my yamaha oil pump is pumping wayyyy too much oil and it is destroying my spark plugs almost immediatedly. I am going to attempt to bypass the oil pump. I have read many times that this is a bad idea because the yamaha oil pump is the most reliable. But with premix gas the engine works supposedly according to the shop where I bought it. And with the oil pump in the loop it covers the spark plugs with oil in about 10 minutes.

 

[boatmon345]

Re: 1992 115 Yamaha going into Limp mode once I go over 4000 rpms, please help

Hi there. I converted from oil injection to premix 50:1 seven years ago on my 97 150, and I do not regret it. It was not difficult to do at all. The reason I did this is because I rebuilt the powerhead, and then I could not confirm that the oil injection system was working properly. So not wanting to take chances, I converted. Just my $.02. Good luck!

Did the water pump and thermostats fix the problem?

 

[Capt Ken]

Re: 1992 115 Yamaha going into Limp mode once I go over 4000 rpms, please help

Its impossible for the oil pump to pump too much oil. If the tank is over flowing, then it will dump the excess oil into the intake and foul plugs but the pump can only pump a certain amount.