Sluggish Mariner 115 hp then takes off. Then repeat for a while????

dwhite0829

Cadet
Joined
Jul 9, 2011
Messages
6
I have an 89 Mariner 115 hp. when I first drop in the water and start it, it runs really rough. During Idle it will spit and sputter and die. Once I get on it, it will take off slow up to about 3500 rpms. Stay there for a while then just take off like a bat... At that point it might go back down a little then speed back up slow down speed back up... it will continue to do this for a while, then will run perfectly for the rest of the day.

I had it in the shop last month, they changed the plugs, said I had the wrong ones in the motor, and found water in my gas tank. When they took it out(I went with them) they hooked it up to their gas tank and it ran fine. they said the compression is good, the stator was a just a small bit off, but not enough to worry about, everything else looked good. I went home and emptied the gas tank, put new gas in and took it out this weekend. Same thing as above. Any Ideas from anybody?

My dad has a jet ski that the plugs will foul up after idling for a while and will do about the same thing, but when he takes off it clears up the fouled plug and takes off fine. Could there be too much gas or oil in the cylinder when it's sitting and foul up the plug?
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: Sluggish Mariner 115 hp then takes off. Then repeat for a while????

Did you flush the fuel hoses when you drained the tank?

It is possible that there could have been foul fuel or drops of water still in those hoses and now in the carbs.

Adjust the trim dead level, remove the float bowl drain plugs one at a time, and pump the primer bulb a couple of times to 'flush out' each bowl, reinstall the plug and go on to the next carb.

You may consider installing a water separating fuel filter to prevent any future contamination of the carbs.

If Dad's ski fouls plugs idling he either has the wrong plugs or the idle is a hair too rich.
 

dwhite0829

Cadet
Joined
Jul 9, 2011
Messages
6
Re: Sluggish Mariner 115 hp then takes off. Then repeat for a while????

I feel pretty confident there was no old gas in the fuel lines, but I'll check the bowls and drain them as soon as I figure out where they are and how to get to them.

Does this sound like an issue with water in the tank since it runs great after a while? Everything I've heard about water in the gas said the motor just shut down, however you can find something that says about anything if you look hard enough...
 

Mi duckdown

Commander
Joined
Apr 14, 2007
Messages
2,575
Re: Sluggish Mariner 115 hp then takes off. Then repeat for a while????

Did you drain the fuel line from the fuel tank to the motor. pump bulb?
 

dwhite0829

Cadet
Joined
Jul 9, 2011
Messages
6
Re: Sluggish Mariner 115 hp then takes off. Then repeat for a while????

Did you drain the fuel line from the fuel tank to the motor. pump bulb?

Yes I pumped all the fuel out of the lines. I drained the carburator bowls earlier today. I bought a fuel/water separator today. I'll be installing that in the next day or two and giving it a try to see what does. Anything else you can think of?
 
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