1995 70hp johnson motor stalling

I have a 1995 70hp johnson outboard motor. 3 cylinder. I bought this boat about a month and a half ago. Ive had it out on the water a few times since ive bought it. It ran good on the test drive and ran good up until about a week ago. Since ive had it it takes a good minute or so for it to start up after letting it sit for a week. A week ago i had it out on the water. Was out for a couple of hours fishing from spot to spot. One time trying to start the motor back up it didnt want to start up. After messing around with it for 10-15 minutes it started back up. I decided to head back to shore. About half way back the motor shut itself off. I look back at the motor and it was smoking a little bit. Just a white-greyish coloured smoke. I didnt start it back up. Someone towed me in. I took it to a retired marine mechanic i know and he determined it was a fuel problem. (At this point the motor wouldnt start, unless he sprayed something in the carbs and it it would start for a second then shut off right away. He did some testing on the motor and he said everything lead him to believe the problem was the fuelpump. He said motor had good spark and everything else but the fuel pump wasnt working. The motor had the original vro fuel pump on it but it is currently set up i have to premix the gas and oil. So i bought a new pulse fuel pump from a local marine shop to replace the vro fuel pump. The retired marine mechanic i know put the new pump on. And he got it running in his driveway with the muffs on. Everything appeared to be running good. Motor sounded great and he could give it throttle and it worked fine. I took it out on the water and it would start up but when i gave it throttle it would stall out on me. I took it back to him it started stalling in his laneway with the muffs on and he adjusted a few things and it sounded like it was running good again in his laneway with the muffs on. I took it back to the water and put the boat in and same problem, the motor stalls on me when trying to give it throttle. He suggested taking it to a marine shop.(I didnt pay the retired marine mechanic anything as he didnt want anything he was just being kind trying to help me out). I called and they said they would call me back when they have time to look at it. In the mean time i am on here hoping somebody can shed some light on what my problem may be.

You've described a engine with either a sticking timer base under the flywheel (advances/retards spark).... or one with fouled carburetors (a common problem).

The high speed jets lay horizontal in the float chamber, in the bottom center portion of the float chamber... way in back of the drain screw. Before tearing the carburetors down.... try carefully cleaning those 3 jets out with a piece of single strand steel wire... solvent doesn't do that job properly.

Okay I will give that a try. Thanks

I ended up taking it to a local marine shop, determined it was a melted heat sensor that was causing the motor to shut off once it reached 2000rpm. New sensor is on the way. It may need new impellors or new fuel pump, but bolts on lower end won't come off so I decided to leave it for now and i'm just going to keep an eye on the motor to make sure it pisses out a steady stream of water while im running it.

A melted (shorted) heat sensor would of course affect the rpm. The normal operation is that if the engine was running at say 5000 rpm and it started to overheat, the heat sensor would cause the S.L.O.W. feature to engage, causing the rpms to drop to 2500 rpm.

The tight/frozen bolts... Use a hand help propane torch to heat and expand the aluminum surrounding the bolts to help free them.

There might be a bolt under trim tab! beware

Update on boat, put it in a local river (first time out on it since i got it back from the mechanics, it still has the similiar problem as before. It was apparently running good at his shop in a barrell of water. In the river it would start fine, i could give it slightly more throttle than before but it would still stall out on me. Giving him a call in the morning.