I replaced my Throttle Postion Sensor because I thought the other one was bad because it would not idle when shifting into gear. I have a SELOC marine manual and followed the direction with DMV (digital volt meter) .

I did the routine of disconnecting the wiring to the ECM to check for a short. I did not have one. I also checked my pins on the ECM harness coming from the TPS and had continuity.From what I read ,it says the ECM might be bad. Is there a for sure way to check with a meter if the TPS is working as it should? I took the following reading with the TPS connected to the harness:

1. Between terminals A and C I had 4.85v with the ignition on.
2. Between terminals A and B I had 4.95v with the ignition on.
3. With C terminal to battery (-) I had .566 v.

Any help would greatly appreciated.

Thanks,
Shawn

Is it setting any codes? The troubleshooting procedure below is from the Merc service manual. I don't know if it's the same as the Seloc manual.

Dave

I read through it and thought I followed all the instructions.Everything I read showed the ECM might be bad, but I don't know if I miss understood something in the directions on making sure the sensor was good especially after installing a new one lastnight. I guess I'm looking for someway to let me know the TPs is sending the right signal to the ECM at idle.

Is there a voltage reading or something that should come out of the ECM going to the TPS to let me know the TPS sensor is good? If so what wire should it go to on the TPS and what should the voltage be? I have a blue, gray and black wire going to the ECM. Continuity showed good from the TPS pins to the ends of the harness before you plug it into the ECM.

I'm scratching my head on this. When the motor is running at idle is there some wires I can connect to with a volt meter to see if the TPS is sending the right voltage to the ECM and the ECM may just not be seeing it?

Dave N, I appreciate the input on this one as well as all the other help I see you have given on this board to the other guys!

I will also use the your document you posted this afternoon and do a couple of more checks.

Thanks,
Shawn

With everything connected and the ignition on, check the voltage from the TPS with the throttle lever being in the idle position.
You do it by piercing the insulation on the output wire, I think it is the middle one. It should show no more than some 0.7-0.8 V.

W/O a scan tool it turns into a diagnostic dartboard. If you have the 2-350 MAGS you could try swapping the ECU from the other engine. I'm saying that if you can't get a accurate reading then this can't hurt tryin'. What is it 3-4 bolts and a couple of connectors.

Unfortunately its a single 502. When I had th engine orginally built back in 2000 the ECM had to go back to Dustin once for adjustments. It worked great for 3 or 4 years. I did notice problems with it idling about 7 months before the engine blew in it. I tried adjusting it myself but no good. I'm just wondering if it was a problem way back when and I didn't have it checked and thought it might be something else.

Now I have the new engine in , it shifted in and out of gear fine when it was on th water hose, but as soon as I back it in the lake and shift it into gear it dies. Thats when I went and started replacing things like a new IAC motor, which didn't seem to help and a new TPS sensor now.. for some reason I have my doubts that it going to work when I put it in the water this weekend.

I just hate paying 75 and hour to have someone look at it, but if this doesnt work it looks like thats what I will be doing.

It is a WHIPPLE motor, not sure if I posted that.