I need help

[brimcfall]

I have a 99 4.3 mercruiser . The boat will idle, throttle , and run fine until.... . When it gets about 165-170 temp on the gauge, the motor shuts off like someone pulled the key. If i wait for it to cool off, i can start it up and get it back to shore, if I'm close enough. If it gets back to temp it will stall again and i cannot start it back up. It has new coil, cap, rotor, plugs. currently putting in thermostat and impeller. nothing seems to solve the problem. all parts replaced have been per tech, or suggestions from other threads, help !!

 

[alldodge]

Welcome
99 4.3 what?
Serial numbers are best but, is it TBI or carb and if carb is it TKS?

 

[brimcfall]

Carb

 

[brimcfall]

Sorry missed the tks question, not sure what that is. Just a diy guy, trying to solve the problem. The dealership near me had it and returned it with the same problem after installing the plugs wires and cap and rotor. Can't count on them. They said they had it running and it ran fine then i took it on the lake again and it did the same thing.

 

[alldodge]

Serial number doesn't show TKS carb just regular carb (either 2 or 4bbl) and TBV ignition

So many dealers (stealership) throw parts at a problem, charge for them and say it runs fine for us. They didn't listen to you and the problem, let's just throw some parts at it and call it good

Depending how long it takes to get to temp (Parts show 160* stat) if might be heat related and loosing spark, or might be running out or gas.

If it's heat you should be able to let it idle until temp comes up and then dies.

If it's fuel then after it dies you can pump the throttle and look down the carb throat and see no fuel squirt down. If you see gas squirt then it's electrical

 

[brimcfall]

ok, i will run a couple of test's and see what happens, thanks for the input.

 

[Scott Danforth]

Check for spark. If you have the original 2-wire distributor sensor, I suggest you spend the $50 on a new 3-wire sensor

Also check the oil pressure switch (not sender). The oil pressure switch controls the fuel pump

 

[tank1949]

Sorry missed the tks question, not sure what that is. Just a diy guy, trying to solve the problem. The dealership near me had it and returned it with the same problem after installing the plugs wires and cap and rotor. Can't count on them. They said they had it running and it ran fine then i took it on the lake again and it did the same thing.

I suspect that you have a ground or connector issue. Start wiggling wires while motor is running.

 

[brimcfall]

Thanks for all that replied. The problem was a broken connector, bouncing around and loosing connection. So electrical was the problem. Thanks again

 

[chs marine service]

what connector was broken?

 

[brimcfall]

It was inside the main wiring harness plug . Rusted from moisture and not broken after all, just cleaned up and dielectric grease and zipped tied it for a tighter fit. Seems like it was bouncing around and cutting out.