1980 Merc 115 - almost left me stranded

[hempfarmer]

I had my boat loaded down with 5 people, shut off the engine and then tried starting it up 20 minutes later. It would turnover but not firing up. It took about 15 minutes of playing with it and eventually got it to fire by giving it full throttle. I have owned this engine for 5 years and nothing like that has ever happened??

With 5 people in the boat the back end was sitting lower than usual. Is it possible that water got in my exhaust problem and caused an issue? Is that even possible? The reason I ask is that the engine was fine for the rest of the weekend. Started up no problem every time and was able to ski all weekend.

 

[Fuzzytbay]

Re: 1980 Merc 115 - almost left me stranded

Sounds like no fuel, did you prime the ball hard before trying to start? Its possible the weight in the boat, and tank location caused the pickup tube to suck air.

 

[mrkris]

Re: 1980 Merc 115 - almost left me stranded

Only starting after going full throttle generally means it was flooded with gas.
Holding the throttle wide open lets more air through the engine which clears the gas. A wide open throttle when the engine is not running prevents gas from entering the engine.

What causes too much gas? (possibly lots of reasons) Maybe you have the opposite (weak spark).

 

[sschefer]

Re: 1980 Merc 115 - almost left me stranded

The motor's 30 years old so I'm willing to bet that your guess is right. With the engine that deep in the water, the back pressure was just too much for it to handle. Once you got the motor a little higher and took away some of the back pressure it ran fine..

Think of it like pushing a basketball into the lake. For the first couple of inches it goes pretty easy but after a foot or so it gets pretty difficult, at three feet it's almost impossible. Same thing is happening to your motor.

Edit.. Just a fyi the engine was flooding because the exhaust back pressure was to great and it was not allowing the cylinder to clear the unburnt fuel so the plugs were just staying wet.

 

[hempfarmer]

Re: 1980 Merc 115 - almost left me stranded

Thanks for all the input. I am actually wondering if I don't have weak spark. I didn't replace any of the plugs this spring but maybe I should be?

 

[sschefer]

Re: 1980 Merc 115 - almost left me stranded

Thanks for all the input. I am actually wondering if I don't have weak spark. I didn't replace any of the plugs this spring but maybe I should be?

I change mine like they're free. I probably couldn't tell you what a bad plug looks like. I also never need to wonder if my plugs are good or not. You do have to weigh your options... Humm case of beer or new plugs... Sometimes the beer wins.

 

[Jacket4life]

Re: 1980 Merc 115 - almost left me stranded

I change mine like they're free. I probably couldn't tell you what a bad plug looks like. I also never need to wonder if my plugs are good or not. You do have to weigh your options... Humm case of beer or new plugs... Sometimes the beer wins.

This is exactly how I do it now. In the spring, drain the LU, replace impeller, fresh LU lube, decarb, new plugs. Takes most of the morning. While I'm running it on decarb I lube the steering tube, the lube points on the motor, etc. This 4 hours and $50 saves a lot of time and heartache the rest of the summer!