50 Johnson Runs when it wants too

" Johnson J150STLCUR
Motor

" Johnson J150STLCUR
Motor on Bass Boat

Motor will not accelerate acts like not getting fuel, no power, low RPM?. Will do this hot or cold. Next time try to accelerate will run fine 5500+ RPM?, 55-58 MPH. At times running at high speed it seems like fuel has been shut off, does not stall but comes back to idle speed (no power) and boat come off plane and stops in water. All this happens at any time without warning. Some times it will run 2 or 3 times out with no problems at all.

This is what I have tried to date to fix problem.

Pump primer ball while trying to accelerate (no change in power)
Push key in while accelerating (choke ?runs worse because of added fuel)

Replaced primer ball
Replaced fuel line from bulked to engine
Replaced fuel tank selector valve
Replaced ignition wires
Replaced spark plugs
Replaced Stator (because of charging problem)
Replaced fuel pump (VRO)
Rebuilt 3 carburetors (Twice)
Cleaned and inspected filter on fuel tank pick-up tube
Cleaned and inspected filter
Inspected fuel tank for moisture
Removed anti siphon valves in fuel lines
Removed primer solenoid cleaned and inspected
Ran on external 6 gal tank (no help)

After rebuilding carburetors motor ran the best it has ever run (thought problem was resolved). After about 6 hours of running and stopping it started all over again. So I went through them a second time figuring something happened in one carburetor. No help.

I don't know what to do next short of replacing the motor (not an option). "

" IT SURE SOUNDS LIKE YOU MIGH

" IT SURE SOUNDS LIKE YOU MIGHT HAVE A FUEL LINE ON THE ENGINE THAT IS COMING APART INTERNALLY THAT IS BLOCKING FUEL FLOW TO THE CARBS,YOU HAVE DONE ALOT OF WORK TO FIND THE PROBLEM SO I'M TAKING A GUESS THAT IT MIGHT BE INSIDE A FUEL HOSE. HARRY "

hook a timing light to a spar

hook a timing light to a sparkplug and lay it on the seat next to you . When the motor acts up observe the flashing light.The ignition system has multiple parts and it may take several tries to find the affected parts.Water in the fuel tank ????

" Herb,

Before any real

" Herb,

Before any real work is done to diagnose a problem, it's a good idea to check compression just to be sure you are starting with a good engine. I'd suspect an electrical/ignition related problem because of the inconsistency. I doubt this is it with you, but a friend of mine has a 200 HP Johnson that has odd hesitation problems. After a full year of tinkering with it he checked compression and found it to be low on one cylinder. After running a can of decarb through it, the compression came up (stuck rings freed) and it runs perfect now. My merc 115 does the same thing every 20 hours (probably rich low speed jet), but it runs great after decarb. Just a thought,

Jon "

" My Johnson 50HP had a simila

" My Johnson 50HP had a similar problem and spent considerable time with the machanics. After replacing the fuel supply line and cleaning the fuel tank filter the problem reoccured.
As a last resort, because it appeared to be a fuel problem, I emptied the fuel tank and put the water hose inside (on fuel pressure) making sure it got to ever corner of the tank. Dried the tank out replaced the fuel, and have had trouble free motoring since. "