94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Help?

[Timearley]

I purchased a 1994 225 Mercury X carbed motor, The oil injection has been disconnected an I run it 50:1. When I started runing it it would idle fine. Give it a little throttle and it would go about 50 yards and start to sound like it was loading up and spit and pop and cut off. You can take it and start at an idle and push it to mid throttle and it will bog out and cut off. Take it at an idle and give it wot and it will hold at 2000 rpm's and start to climb and take off and run 72 MPH at 5300 RPM. If you pull back to mid throttle it will start to stall to the point it will cut off. You can start it right back up and the same thing happens. Two different mechanics are stumped, this is after having the carbs rebuilt, new stator put in, New TPS installed, Throttles set, Carbs adjusted, New fuel filter. If anyone can help with suggestions I would greatly appreciate it. I have spent alot on this motor. Any suggestions before I go bald. :

 

[Texasmark]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

My guess is that you have a wiring problem under the flywheel with the stator/trigger wiring. As the spark advance moves across the power band from right at TDC at idle to like 22 BTDC at WOT, a wire must be chafing and rubbing against the flywheel shorting it out.

Mark

 

[Timearley]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

My guess is that you have a wiring problem under the flywheel with the stator/trigger wiring. As the spark advance moves across the power band from right at TDC at idle to like 22 BTDC at WOT, a wire must be chafing and rubbing against the flywheel shorting it out.

Mark

This is a 12 pin stator. Is this were you are talking about were the wires come out from under the flywheel and plug in. or is there another set of wires to look at.

 

[Faztbullet]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

What is your voltage at idle? Could possibly be bad ECM or CDM module/s.

 

[Timearley]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

What is your voltage at idle? Could possibly be bad ECM or CDM module/s.

I am not sure how to correctly check the voltage at idle. I have been told several ways and my mechanic has performed one way and he is not sure of the correct way. I have a 3 wire TPS one blue wire with tan stripe one blue wire with orange stripe and the black ground wire. I have checked it across the two blue wires and had 4.0 volts in nutral with it dropping to 1.35 volts at wot. Another way was from the center wire to the black wire the voltage was reversed being .95 at nutral and 3.75 at wot. The third way was performed with the center wire and the black ground wire also disconnecting the tan wires to the temerature sending unit. The voltage was very similar to the previous test with the voltage being at .95 at nutral and 3.75 at wot. The boat was run after the various setting and the problem still persist. I was also told to set the TPS all the way counter clockwise and start advancing it from there a screw width each test run. The voltage with the TPS set to the most counter clockwise position was .026 at nutral and 1.35 at wot. The problem was a little better not much during this test. The TPS was moved clockwise one screw width and set. A test run was mad and it was still very similar to the previous test. Any advise or suggestions would be greatly appreciated.

 

[Texasmark]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

What is your voltage at idle? Could possibly be bad ECM or CDM module/s.

Help me understand this man. Why would he have a CDM or whatever the other one is at mid range only? I have had them fail for several reasons, but not at mid range and work perfectly, especially at WOT. I worked capacitor discharge systems my entire career and never had a mid rpm problem.......buttttt anything is possible.

Mark

 

[Texasmark]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

This is a 12 pin stator. Is this were you are talking about were the wires come out from under the flywheel and plug in. or is there another set of wires to look at.

A visual inspection below the FW would be the first order of business. If nothing there, then pull the flywheel and look for insulation rubbed off where the flywheel could/can contact the wiring you mentioned.

Mark

 

[Timearley]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

A visual inspection below the FW would be the first order of business. If nothing there, then pull the flywheel and look for insulation rubbed off where the flywheel could/can contact the wiring you mentioned.

Mark

I removed the coil wrap around the 12 wires going to the stator 6 green and 6 white. I found no problems at that location. I will try to remove the flywheel later and check that location. I also visually inspected all of the wiring on the motor, I found no problems (nicks,scrapes, cuts etc) Thanks for your info it has been a help to me as I try to figure this thing out. I know when it is found it will be something sinple. I'll touch base again when I get the flywheel off.

 

[Faztbullet]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

Why would he have a CDM or whatever the other one is at mid range only?

This is a carb motor with no trigger, it uses a TPS,CPS and other sensors to tell ECM what to do. This year motor had a ton of updates was bad about CDM modules failing(updated kit now),harness connectors and shift diode problems to name a few..A CDM is just a pack and coil built together and the stator bobbin's(6 of them)charge each CDM and common connected thru the blk/yel kill wire. A CDM can be bad and effect the adjacent module buy backfeed thru the kill wire. Since the problem is on low it it should be easy to find by test running engine still on trailer backed into water. I would check the harness connections first along with grounds on CDM,\'s, make sure have the updated modules then I would take a timing light and check timing and spark on each cylinder when it happens. Below is Mercury TSB on these motors.....
View attachment EN_20.PDF

 

[1nebel0]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

Faztbullet is a Mercury mechanic and you are lucky when he chimes in....Sure glad I don't own this strange beast... sticking with the bridgeports and 200hp fishing motors...

 

[Timearley]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

This is a carb motor with no trigger, it uses a TPS,CPS and other sensors to tell ECM what to do. This year motor had a ton of updates was bad about CDM modules failing(updated kit now),harness connectors and shift diode problems to name a few..A CDM is just a pack and coil built together and the stator bobbin's(6 of them)charge each CDM and common connected thru the blk/yel kill wire. A CDM can be bad and effect the adjacent module buy backfeed thru the kill wire. Since the problem is on low it it should be easy to find by test running engine still on trailer backed into water. I would check the harness connections first along with grounds on CDM,\'s, make sure have the updated modules then I would take a timing light and check timing and spark on each cylinder when it happens. Below is Mercury TSB on these motors.....
View attachment 227126

Thanks for the feedback. I will have my mechanic check these items. To gve a better discription of how this motor acts when the motor is in idle all is fine, when you advance the throttle to mid throttle it will sputter and cut off. If you give throttle just barley above idle the motor will sound like it is loading up you can advance and decrease the throttle and the motor will idle at that rpm about 1300. If you try to advance it any more it will sputter and cut off. To get the on plane you have to go from idle to wot and the motor will bog and begin to pick up rpm's slowly. It will then start to increase RPM's reather rapidly and will get on top. You can run 72 + MPH that is the fastest that I feel comfortable running this hull ( Keywest Stealth Flats Boat) You can pull the trottle back to mid range and the motor will drop down and back up in RPM's and settle in approximately on the RPM's you wanted. It is not smooth at all. once the Rpm's are settled into it will run on and on. when you come off plane you will probably cut off when the boat comes down off plane. I hope this will give a little more insight into this problem and maybe additional recommendation. I will try to check the above recommendations. Thanks for your input.

 

[Texasmark]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

Thanks Fazt. Geez. Lot more there than just a CDM.

Mark

 

[Faztbullet]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

Have tech check the alternator output as weak or overcharging will affect ECM....

 

[Texasmark]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

I have to apologize for butting into this thread. I should have realized at that hp it would be EFI, of which I know nothing, and to make matters worse, I have a '94 sales brochure in my file and it's featured. Must have been having a senior moment.

Mark

 

[Faztbullet]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

Its not a EFI its a carb motor with electronics!!!!! :nightmare:

 

[Timearley]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

Its not a EFI its a carb motor with electronics!!!!! :nightmare:

I have checked under flywheel no problems visible. I have not checked the output voltage yet, I will do that today. I did get very fine tuned on the voltage for the TPS, .95 at idle and 3.75 at WOT. this was cahlenging due to tightening the screws the voltage would change slightly. I ran the boat yesterday and it still at low end and mid range throttle was slugish and would cut out and cut off if you did not go to full WOT throttle and it would climb out slowly and then increase in RPM. My mid range throttle was acheivable until you got down into the lower RPMs below 2500 and the motor would begin to stall and cut off. I dont know if this helps you any in what advise is given but I do appreciate your help. I feel I must put the effort forward to figure this out. Very strong good running motor I ran it 67 MPH yesterday no problems. I will check the voltage from alternator today Thanks.

 

[Texasmark]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

Its not a EFI its a carb motor with electronics!!!!! :nightmare:

Well then they made one back then because it has 225 and EFI clearly decaled on the cowl. Geez, senior moments are overwhelming me. I just pulled the catalog after typing the first sentence and saw that all the big engines were EFI; thought they might have had both was the reason for looking. Puzzled I looked again at the date of the catalog and it was 1997. Oh well. :blue:

Looking back I see that you had noted that earlier in the discussion.

Mark

 

[Timearley]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

Have tech check the alternator output as weak or overcharging will affect ECM....

Faztbullet: My mechanics have appreciated your responce to this problem. They are at wits end about this problem. We have done as you said and checked the altenator output that is within the approved range at an idle and reved up. As wI stated before we have put a new stator, new TPS set at .95 idle and 3.75 WOT. Checked for bare or fraied wires under the flywheel, Changed props, I was running a 4.50 26P, changed to a 4.25 X 23 and also a 4.25 21P the bogging out in mid range throttle continues. I have found that if I increase the throttle with motor out of gear, increasing the throttle very slightly to just below 2300 rpm's it will bog, spit and sputter. popping like a backfire. it is the same thing it is doing when you are triing to take off and get on a plane. Mid range is not responding correctly.If you increase the throttle to above 2300 rpm's the motor will rev up like it is suppose to. Any advise would be appreciated. The motor is a good motor and I can't afford another one. Thank for all of your help.

 

[Faztbullet]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

put a small prop on it say a 15 and take it to water and run on trailer. Take a timing light and check that ECM timig is advancing timing thru the rpm increase...

 

[Faztbullet]

Re: 94 225 Mercury cuts off mid range throttle. Idles fine, wot fine 72MPH Please Hel

Install a small prop like a 15 pitch and test run on trailer, check that the ECM is advancing timig with throttle increase.