'98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

[4winnsskipper]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

what are my switch boxes?

 

[Big flop]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

Follow the green wires from the coils. They lead to
the switch boxes. Two electrical boxes STB (right) side of motor
they should have 10 wires per box. Two boxes one on top
of the other (stacked).

 

[jeffersondodson561]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

Trying to speed read through all of this, did you rebuild/check the mechanical lift pump? I noticed that the port side plugs were the most wet. The mechanical fuel pump is on the port side, I would take the mechanical fuel pump off the block and with a pair (meaning qty. 2) of vice grips, GENTLY put pressure on the square fuel pump housing (trying to simulate the fuel pump having even torque) where the two bolts would go to the block. Prime primer bulb and look at the pulse hole on the back of the fuel pump (where the backside attaches to the block). If you see any fuel coming out of that hole, time to rebuild the fuel pump.

 

[4winnsskipper]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

Trying to speed read through all of this, did you rebuild/check the mechanical lift pump? I noticed that the port side plugs were the most wet. The mechanical fuel pump is on the port side, I would take the mechanical fuel pump off the block and with a pair (meaning qty. 2) of vice grips, GENTLY put pressure on the square fuel pump housing (trying to simulate the fuel pump having even torque) where the two bolts would go to the block. Prime primer bulb and look at the pulse hole on the back of the fuel pump (where the backside attaches to the block). If you see any fuel coming out of that hole, time to rebuild the fuel pump.

the motor is an efi engine, the mechanical fuel pump simply fills the VST tank where the high pressure pump pressurizes the fuel rails, then the fuel injectors do the injecting.

 

[jeffersondodson561]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

the motor is an efi engine, the mechanical fuel pump simply fills the VST tank where the high pressure pump pressurizes the fuel rails, then the fuel injectors do the injecting.

Is the fuel pump on the block? So what is the difference of a fuel pump on a carbureted vs. EFI? It can still leak into the crankcase.

 

[4winnsskipper]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

yeh its on the side of the block. to tell you the truth im not up on exactly how a 2 stroke injection system works. I know the motor is oiled through the gas/oil mixture, im not sure HOW though.

 

[4winnsskipper]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

well new update, motor has improved slightly with the warmer weather, it's not as hard for it to start and run well, still will stumble die, then after a few minutes of warming up and while pulling away from dock in gear, the motor just surges to full life, literally, it'll be stumbling a little, bogging down, then it revs up as if i hit the throttle forward more, but i don't, it's as if the motor catches up, stops stumbling and runs where i currently have the throttle all of a sudden then runs like a champ rest of day with no other issues.....

TPS is now my leading culprit, or a second shot is ECU. How can i fully test TPS? io set the tps base voltage throttle closed to spec in manual, but if it's acting up sending incorrect signals to ecu it would explain all of this... also marina wants 400+ bucks for a new tps! where can i get a new one at a normal person price?

 

[4winnsskipper]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

Trying to speed read through all of this, did you rebuild/check the mechanical lift pump? I noticed that the port side plugs were the most wet. The mechanical fuel pump is on the port side, I would take the mechanical fuel pump off the block and with a pair (meaning qty. 2) of vice grips, GENTLY put pressure on the square fuel pump housing (trying to simulate the fuel pump having even torque) where the two bolts would go to the block. Prime primer bulb and look at the pulse hole on the back of the fuel pump (where the backside attaches to the block). If you see any fuel coming out of that hole, time to rebuild the fuel pump.

well i just rebuilt the mechanically pump, was fairly easy actually. i did notice i had rubber check valves and the new kit came with nylon which are apperently the new style. i didn't know which bolts went into the block so i wasn't able to test the pump with the test you suggested...however i did not the gaskets closed to the pulse hole were wet right where the pulse hole is (wet as in had gas on them) which would suggest there was a leak? im not sure... either way put it back together and it started the motor, ran fine but the trouble comes in mainly when motor is cold with a load so we'll see when i can get it in the water again if that fixed or atleast helped.

i think i might of ruled the TPS out, i did the merc test and set the tps per the merc manual and it increased smoothly and had a final max wot voltage per manul (engine off, key on, port temp sensor disconnected)

side note, after rebuilding this pump, i still have no clue how the heck this thing pumps fuel!!! i get the pulse hole supplying vacuum but from there im lost!

 

[rld1017]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

I had this same problem Boat would run 60 mph but would not run at a lower RPM .I tested everthing . durnning this problem I broke a throttle cable. When I open my control box I found the kill switch was rusted bad due to water. I replaced it and have not had anothere problem . I do electronic work and all I can figure was the resitence was low and computer was creating problem It cost me 10 dollals to fix. You may get lucky Ronnie

 

[lilngineer]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

Did you ever find out what the problem was? I have a 240
EFI with the exact same problem. After many parts and adjustments my problem remains. I am thinking ECU?

 

[Chewie]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

I was also waiting to see the outcome of this one. I have a 1996 150 EFI that exhibits a very similar problem. With mine, it seems to be tied to temperature- The colder the air/water temp, the worse the issue is.

 

[4winnsskipper]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

I have only improved not solved the issue. I put new plugs, plug wires, i rebuilt the mechanical fuel pump, new fuel bulb, all new fuel line from fuel tank pickup nipple to engine, i tested every part of the fuel system per the manual, all ok, even fuel pressure, i even bought the official merc spark tester, i get spark on all cylinders no problem..... it has to be electrical, perhaps the idle control boxes is my next step... if it's not that then injector(s) shot which i have a hard time believing.... anyway i'll let you know

 

[ufm82]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

Dude, I'm feeling bad here. Your "****ty idle" sounds exactly like my '93 EFI 150 does. ( But I didn't think I had problems...LOL) And I like it! But mine runs great all the time- no issues on the water like you're having. If you fix you idle I'd be very interested to hear the fix.

 

[Chewie]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

Thanks for the update. Sorry that you're not having any luck with getting to the root of the problem.

If I get ambitious on looking into the issue with mine, I will be sure to post results. Letting mine idle at the dock for awhile seems to take care of it, but that can take awhile...

 

[raymor]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

Have you tried putting an inductive timing light on each of the spark plug wires to see if you have a good steady firing on all the plugs. I have a 2005 115 hp 4-stroke and have a low rpm misfire. Using the timing light found it to be on #3. Think I have a bad coil, but checking the ohms on the primary and secondary says it it good. So unless it is breaking down I don't know what it is. Since the coil is $158 dollars I want to make sure that is the problem.

 

[Faztbullet]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

Think I have a bad coil,

Swap the plug and see if probem follow it, that coil fire 2 cylinders at the same time so if coil was defective it would show on other cylinder that coil fires. Could also bee a bad wire from coil or burnt inside plug boot.

 

[raymor]

Re: '98 Mariner 150 mag efi stumbles/dies for first 5 minutes then runs like champ

Swap the plug and see if probem follow it, that coil fire 2 cylinders at the same time so if coil was defective it would show on other cylinder that coil fires. Could also bee a bad wire from coil or burnt inside plug boot.

Faztbullet I did swap the plug wires (2 and 3) and the intermittent firing followed the swap. The boot looked pretty clean and I did check the secondary with an ohm meter and it was in the spec called out. I also moved the leads around to make sure I did not get any intermittent ohm readings. This is why I'm leaning toward a bad coil. Do coil break down like this as you have far more experience than I do on these motors.