Inconsistant spark on bottom 2 cylinders? Need some help

[mkeleher]

Hello all,

I am needing some help getting my 1991 2.5 LITRE mercury 200hp running correctly. Took it out to the lake yesterday and only got the boat up to 45 mph. I knew the motor wasnt running right cause a norris craft with a 200hp should go at least 65mph. I will mention that I just bought the boat and this was my first time out. 2 of the plugs were fouled out when I got home. Bought 6 new NGK plugs today to replace the old champion plugs. Wanted to run a spark test on all the new plugs to make sure it wasnt any of the 6 ignition coils. Top 4 plug on each side held a consistant blue spark which I know was good. The bottom 2 plugs on each side threw a blue spark but it wasnt holding the spark. It was an inconsistant blue spark. Could this be my potential problem with the motor and what steps can I take in order to correct the problem. I know this boat will fly if it is running on all cylinders, im looking forward to hearing any suggestions. Model of motor - 0C291520

Thanks,
Max

 

[TD_Maker]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

Just curious. How many RPM's were you turning? If the motor was running in the normal RPM (5250 -5500) range, then your problems may be elsewhere. May be a prop issue. May be a motor issue. Need to have a base line to start.

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

Unfortunetly the RPM meter was not working. It wasnt turning high RPMs. It felt like it was only running on 4 cylinders

 

[TD_Maker]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

I would get the tach issue (RPM Meter) repaired and start from there. You can throw parts at it or just go by "feeling" alone, but it could be very expensive to do it this way. One thing I learned about Mercs.... you have to attack them logically, or they will drive you crazy. Just my two cents.

 

[CharlieB]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

First thing to remember, There is NO RETURN on electrical parts, never assume any part is bad until tested, TWICE, and proven bad.

Most tachs are pulse driven off the grey wire of the rectifier/regulator, if your V6 has twin reg's switch the grey wire from one reg to the other. If not, remove the rec and Ohm test to see if the diodes are working correctly, a bad diode often first noticed as a inaccurate or dead tach. But due to that NO RETURN thing, prove it before ordering a new part.

Inconsistant spark could be a dying trigger wire, bad coil ground, poor plug wires. A DVA meter or DVA adaptor for any Volt/Ohm meter is needed to accurately test trigger output. I'd first remove all coils and clean all contacts and retest spark.

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

Spark plugs were incorrect and timing was off. Guy at autozone didnt match up the same plugs I had in it so they werent functioning right on the motor. Thanks for all the advice

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

Onto the next issue. Took the boat out and it ran good for about 10 Minutes Wide open or until the motor heated up. Ran the motor about 50 MPH for 10 minutes and all of the sudden the motor just shut off. Tried to start it and it was flooded. I waited 5 minutes before starting again and it fired up. Thought it might have just been a loose connection. Well, decided I would turn around and head back to the landing. Ran it about 48 MPH and right before I got to the landing, boom motor shuts off again. Water pressure is good and the motor will always start back up, but as soon as it get hot enought it shuts off. There is no alarm that goes off or anything. Spoke to a local marine tech that lookd at my motor previously and he said it could be the stator and reactifier not cooresponding with each other and telling the computer to shut down. Guy that owned the boat before me had a used stator put on the motor which didnt exactly match the reactifier that was on the motor. So the next series of questions are 1. Could the stator be the culprit of the motor shutting down? 2. How can I make sure it is the reactifier and not stator or vice versa. Would had to throw money into a part and not be sure that is what it is

 

[CharlieB]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

First rule, there is NO RETURN on electrical parts. Test and re-test to PROVE the fault before even thinking of ordering anything.

A rectifier does not know anything, it is only an electrical valve, it has to handle sufficient amperage or it will melt and die. Period.

A Volt/Ohm meter is needed to test battery voltage at the battery, then start the motor and run it up to 2500 and recheck battery voltage, it should be higher. This will show the charging system is charging. Turn off the motor and remove the rectifier, switch the meter to Ohms test the rectifier from one yellow to the other, you should have NO reading. Test from one yellow to the red, then reverse your leads and test again. You should have a reading when connected one way but not the other. Repeat on the other yellow to red. You should have the same one way and not the other. Rectifier should be fine, reinstall.

You need a DVA meter or a DVA adaptor to use with your volt/ohm meter. Test the stator and triggers following the well laid out instructions in the CDI Ignition Guide

ISSUU - CDI Electronics Practical Outboard Ignition Troubleshooting by CDI Electronics

Third, you need a fuel pressure gauge to screw onto the fuel rail and check fuel pressure. Fuel pumps can maintain pressure easily at an idle and reving in Neutral as the motor does use much fuel until under serious load. You need to see if pressure drops just before the motor fails.

Repost you findings and any further questions.

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

This is VERY helpful. Thank you for the advice. I will give these tests a shot and report back my findings.

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

One more scenario I want to add is the first time the motor died going 50 we found out the battery had died. Went and bought a new battery. At least the second time the motor died we could get it back started right away since we had a fully charged battery. Wanted to add this peice to the puzzle so I have all the infomation and tests I need for the weekend when I am working on it. Sucks I will be working on the motor rather than out on the boat this weekend.

 

[CharlieB]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

This could be your 'Aha!' moment.

EFI requires a minimum voltage to function. I the rectifier is bad, no tach, and no charging. The battery gets low and 'Bingo', the motor dies.

You really need to test that rectifier, prove it good/bad. I'm betting it is bad but that 'NO RETURN thing I rather you test and prove it before spending for a new one.

On the hose at home use a simple volt meter, check battery voltage, it should be near 12.5 Hook up the hose and start the motor, watch the battery voltage, running the motor speed up to 2500 and watch the voltage, it should start to rise over that earlier reading. If not it is most likely bad, BUT, it is possible that the charging windings in the stator have gone bad so you really need to disconnect the rectifier and Ohm test to be sure.

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

@CharlieB

Havent gotten a chance to check the stator but did check the volts coming from the battery. No charge on the battery after motor is started, put into gear, and brought up to 2000RPMS. Tach is still not working at all. My question is if it is in fact a rectifier, does it need to be a water cooler rectifier? The outside of the motor says 2.5 liter but the computer on the inside says 2.4L in case this help determine that part that needs to go on the motor. How do I know if it is a water cooled rectifier or not?

 

[Faztbullet]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

A 2.4 ECU will not run on a 2.5 as fuel curve in mapping is different. Look on the heads and get casting number to see if a 2.4 or 2.5L. Also

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

From what I found it looks like 150 head? Also, if the stator was bad would the motor still run past a certain RPM? I connected the gray tach wire to the yellow wires from the stator and still nothing. Battery does not charge when motor is turned on. Looks like the rectifier is on the back end of the motor. Does that mean it is not a water cooled rectifier? I want to make sure I purchase the correct rectifier if that is for sure the problem. This motor looks like it has been peiced back together with different parts so its hard to find the correct diagram. I looked at the breakdowns on Iboats and it gives me the option of a 1991 2.5L 200efi motor but the actual internal parts on my motor says 2.4L with a casting # on heads as 96422. From all the symptoms im still leaning towards the rectifier. Killed one battery, No charge on new battery when running, tach doesnt work, motor always starts back up, and motor cuts off when it gets too hot or runs out of volts. The only thing that is holding me back is the possible bad stator. Im not sure how to test the stator since im not exactly the best with electrical components. Can someone breakdown the steps to checking my stator?

 

[CharlieB]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

TEST the rectifier before ordering a new one.

You need to be sure which part is defective.

The stator has three sets of windings, low speed ignition, high speed ignition, and battery charging. So it is possible that the stator could be at fault which is way why highly recommend testing everything before spending any money on NONE RETURNABLE electrical parts.

NEVER ASSUME anything, test it properly and know which parts are bad.

Not to get on your case so much, just want to help save you some money.

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

Im going to a friends house tommorrow to run these tests. He is better with a meter than i am. After we run the tests ill report back with the findngs. Im gaining tons of knowledge from u guys and really appreciate your input. If i can get it fixed myself maybe my wife will leave me alone.

 

[Faztbullet]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

Sounds like someone put a old 220EFi on a 1991 midsection, check the compression as this is a chrome bore motor.

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

110 accross the board

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

Update on Rectifier/Stator. Found this thread online which I tried on my rectifier.
"
Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.

Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.
Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier "

The 1st paragraph checked out, but the second paragraph in bold did not. I connected both the positive lead and negitive lead to the red wire from the rectifier and got nothing either way that I tried. During this process I took the rectifier off to take a closer look at what I was working with. Turns out it is a water cooled rectifier. Any suggestions on where I find a comparable one at a good price? Its a 40amp

 

[mkeleher]

Re: Inconsistant spark on bottom 2 cylinders? Need some help

Checked yellow wires coming from stator with multimeter. Did not get any ohms out of either wire. Also, I was told today that my cranking batteyr could have burned out the stator since it was only a 845 cranking battery rather than a 1000 amp cranking battery thus making the stator work overtime to try and charge the battery. Stator may have been getting hot every 10 mintues then shutting everything down. Thats probably why after the motor cooled off the motor would start back up again. This motor is giving me a fit deciding whether I have a stator problem of regulator problem. I want to order one of the other to try and fix the problem. Any suggestions before I order a stator? 50/50 shot right?