Need help: Stalling prob on mariner 150hp

[will941s]

Been on here a few times w/ my motor: 1996 Mariner 150hp Magnum 3, carbed/oil injected

Some background on it, at first when I got it, it wouldnt pee, or idle. But would hit WOT. I have rebuilt the carbs, replaced the fuel pump, new water pump, new fuel water seperator filter, and a new inline filter on the motor. No leaks on the fuel, and the primer bulb stays hard all the time. It pees and idles great now. Compesssion as of last weekend was 110 psi EVEN

What's happening now is it'll start great, and if you take off after it warms up, it will run like a bat out of hell. As soon as you let off the throttle (no wake zone) and hit it again it will bog down and die at about 2-3,000 rpm's. It'll start right back up everytime, and if you use the warm up lever, it'll max out all day long. If you slowly take off and "feather" the throttle through that range, it'll hit WOT...and maintain it with a load. It seems as if, if you let it sit for awhile, it will hit WOT right off the bat....then the problem will start the next time you let off the gas.

Any thoughts on where to look next will be GREATLY appreciated.

 

[will941s]

Re: Need help: Stalling prob on mariner 150hp

Planning on test running it on a isolated 6 gallon tank....think this is a good place to start? Anyone else have any other suggestions?

 

[Sunfish12]

Re: Need help: Stalling prob on mariner 150hp

Check for spark on each cylinder and if you can pull plugs when it acts up and check for water intrusion on plugs.

 

[will941s]

Re: Need help: Stalling prob on mariner 150hp

Thanks for the reply, the plugs look good, no signs of water intrusion and they all look exactly the same. It's just wierd because if it sits for a period of time, it will hit WOT like a bat out of hell, and maintain WOT all day long. It's just when you slow to idle and hit it again it will stall...unless you VERY carefully feather the throttle. You can feel it kind a surge a little bit, then it'll take off.

I can't test it by pulling the wires because it's crazily unsafe... when it does decide to take off it will launch whoever is back there right over the transom because it takes off so fast. Can't test it while putting it on the trailer, it's a 19.2' KeyWest and I don't believe the trailer can handle that torque....my park brake on the truck and tranny can't handle the pushing either. It don't do it with the warm up lever, just with a load.