I have a 95 Merc 200, EFI that is having problems starting. I broke down on Fork Friday and had it worked on. The TPS was adjusted and it ran better than ever from the ramp. The next time I tried to start the motor it would crank. I tried giving it some throttle and it fired right up. For the rest of the day it started intermittently, sometimes taking throttle. Any ideas? I can't keep spending money on it with it continuing to have problems.

My fuel pressure was to speck on the fuel pump and none of the filters were clogged.

Might be clogged injectors. Depending where you are located you ought to give Ronnie at Texas Machine Works in Grand Prarie a shout! He's a good honest guy that knows his stuff!!!

I have seen problems with the "O" rings in the fuel rail deteriorating and contaminating the injector screens. The "O" rings on the injectors can drip or leak. Just another ethynol problem.

I've sent a few sets of injectors from engines with starting/driveability issues to InjectorRX in Houston. Every time they tell me that the solvent came out black when they started cleaning the injectors. That's the fuel lines dissolving in the ethanol, and being deposited in the injectors.

I add Marine Stabil or Seafoam to every gallon of fuel I run in my boat now, and advise anyone that asks to do the same thing.

thanks for the input guys. I run marine stabil in every tank and sea foam about every other tank. I will keep tinkering with it. I have looked on Mercury's website to see if can or should replace my TPS, but I can't even find it in the schematics.

I would`nt think your TPS is bad if it helped when it was reset. You will need to have a fuel pressure test to check for leaking injector or "O" ring.

Could be alot of diffrent things ,,but I would put my money on the water temp sensor in the port head. Its telling the computor that your engine is cold all the time,,causing a rich condition,,thats why it starts when you open the throttle because you are giving it more air when you open the throttle. I have a DDT to test merc efi if you are in my area. Thanks Cary.

Fuel pressure was tested last wknd when my TPS was adjusted and everything came back fine. I will look in the water pressure sensor.
Thanks for all the advice

I ran the boat this past weekend with the same result. The motor cranks perfectly when its cold. After I run for a while I have to give it throttle to start. Could this still be the water temp sensor? It seems counter intuitive to me that if this sensor was bad it would crank fine when it is cold, but then need throttle once it warms up.

Im beginning to think you may have a manual fuel pump diaphram with a small leak or you have a leaky injector or "O" ring in the fuel rail. Best just to change the diaphrams but you will need a shop to perform a fuel pressure test on the injection. Needs to hold 32psi w/motor off for several min.

Thanks Gary - I will see what I can figure out. My motor runs good, I just want it to run RIGHT.