Mercury 115 HP OB

[MJE]

I have a Mercury 115 HP OB that I beleive is an early 80's model. I have owned the motor since 1990 and it has always ran very well. I have use it very little since 1990 and it had not been ran for the past two years. Recently I decided to take it out so I put on the muffs and started the motor. It started fairly easy and seemd to run ok. I shut if off and as the gas was two year old, I drained the tank and re-filled with fresh gas. When I took it to the lake, it ran just fine for the first two days. On the third day I began in a no wake zone, so I ran the first 30 minutes at a very low speed. Whe I tried to open the motor up, the boat would not plane off, it ran as though it was at 1/2 throttle. After a number of attemps, it finally planed off one time, but when I shut it down and opend the trottle again it would not plane off. I took the boat out and replaced the six plugs. When I went back to the lake, the motor wouldn't start. I appreciate and advice or suggestions. Thanks

 

[AMD Rules]

Re: Mercury 115 HP OB

First steps: Check for compression, spark, & fuel.... no use going further until you know those are ok.

Given that it sat idle for a while, you should probably clean the carbs anyways.

After that is all checked out AOK , move on to the link & sync procedure to ensure the throttle and timing settings are good.

What is the serial number of the motor (need to know s/n to determine ignition type)?

 

[nomoe]

Re: Mercury 115 HP OB

I have a Mercury 115 HP OB that I beleive is an early 80's model.

My experiences with the same engine under the Mariner name.

Usually lack of power can be traced to insufficient fuel or faulty wiring.
Fuel related
1. Cracked or clogged fuel line or filter.
I'd replace all fuel lines and primer blub, and check fuel tank pick tube.
2. Carbs, in my case its always been a stuck float, usually occuring when I've forgotten to run engine out of gas and stored the boat for a year or longer. Easy to fix, just loosen 2 screws holding each carb bowl. I then take a straighten paper clip and insert into gap and gently pop the float down.
However, I don't think this is your problem as yours ran for a few days.

Electrical
I've noticed on mine that some of the ignition wiring on the engine has begun to degenerate. In particular the rubber insulation is getting brittle. I found several spots where cracks had formed allowing moisture to enter and corrode the wire away inside. You might want to poke around looking for cracks in insulation. If you find one remove a little bit to see what condition the copper is in. Splice a new piece in and seal with good electrical sealant.