What should I check next?? 3500 RPM at WOT

[Jace LaValle]

Boat starts right up and idles just fine. But once I begin to accelerate it only gets up to 3500RPM at WOT. It seems to be running rich maybe (too much oil). I'm always confused between rich and lean. I replaced the spark plugs. Cleaned the final filter in the VST and the filter in the fuel regulator. The fuel in the VST was light blue, so it looked like properly mixed fuel I think.

The boat ran fine last time we took it out, then it was in dry storage for a week or two, and when I went to take it out again I couldn't get it past 3500rpm.

2000 Challenger 2000 w/ 240hp Mercury M2

 

[Dr Honda]

to start.... What engine do you have?

 

[Jace LaValle]

to start.... What engine do you have?

Wow, im a dummy. 2000 Challenger 2000 with 240hp Mercury M2. I don't have the exact serial number on hand but I looked at it yesterday and the corresponding build on Mercury Parts Catalog was 0E373939 thru 0E384499.

Thanks in advance Dr Honda, couldn't figure out how to tag you but was hoping you would see me plea for help!

Also I have already disconnected the guardian.

 

[Dr Honda]

OK... now he have a place to start.


These engines are strange... they will start, and idle very smooth, on only 3 cyls. So......


If the engine is smooth up at 3500 RPM:

1) Check all the spark plugs for fire. If you have a bad coil, or pick-up... you may not be firing all plugs.

2) Check the compression on all the cyl's.

If the engine feels like it's sputtering at 3500:

3) Check for a "Throttle Guardian" in the helm. If you fid it... REMOVE IT !!!

4) Make sure the neutral switch is working. (it's in the levers)

5) Look for chaffed wires coming out of the flywheel.

 

[Jace LaValle]

It's smooth. Just feels like I'm at half throttle instead of full throttle. I ordered a spark plug tester and a compression tester. I also have a port side temperature sensor on order just to rule it out. Will report back.

 

[Dr Honda]

changing the port side temp sender is always a good "Tune up" item... but it won't keep the engine from reving up. If it's smooth... there's a couple cyl's not firing for one reason or another. Either spark, fuel, or no compression.

Do your tests, and let us know what you find.

 

[Jace LaValle]

Okay... Is it possible it's only running on 2 cylinders. I got my inline spark tester today and it only lights up on cylinders 4&5.

 

[Jace LaValle]

Plugs from left to right 1-3-5-2-4-6

Cylinder 3 doesn't even appear to have any fuel on it...

 

[Dr Honda]

Yes... it could be ruining on 2 cyls... but it's normally rough at idle.

#'s 3 and 2 (if I read your post right) aren't firing at all.


Lets get a compression test, and post up the numbers on all the cyls.

 

[Jace LaValle]

Also I am going based off of the numbers on the CDMs port side 2-4-6 top to bottom and starboard 1-3-5 top to bottom.

Compression seems normal

1- 120psi
3-110psi
5-115psi
2- 110psi
4-115psi
6-120psi

 

[Jace LaValle]

Yes. From the looks of the spark plugs. 3 & 2 don't seem to be firing at all. These spark plugs were just replaced and engine has only been run during testing since.

 

[Jace LaValle]

A bird almost pooped on my head today but it hit the flywheel cover instead, and then some scorched wires caught my eye... the wires coming from the trigger assembly are very corroded just before the harness.
1) could this be causing my problems?
2) Can I repair the wires or will I need to replace the entire trigger assembly?

 

[Dr Honda]

The compression is low... but should still run.


for the other questions...

1) Yes. But post a pic so I can see what wires they are.

2) Post a picture, and I can tell.

 

[Jace LaValle]

I didn't take a picture but I will take one tomorrow and post it. I think they're all connected so I dont think thats it but I would still like to repair if possible.

If thats not it I'm thinking the control module maybe?!

 

[Jace LaValle]

 

[Jace LaValle]

Also is an inline spark tester be sufficient or should I be using a proper spark plug gap tester?

This is what I have.

 

[Dr Honda]

The tester is fine... but those wires are ugly. AND... I'm guessing it has something to do with your ignition issues.

I would pull the pins out of the plug, and replace the bad sections of wire.

 

[Jace LaValle]

Okay, I will give that a go. What would be our next step if that doesn't solve our problems? Want to have my flow chart ready! lol

 

[Dr Honda]

ok....


1) Fix any "Issues" wires.

2) Pull all the electrical conections for the ignition, and make sure the pins aren't corroded. Reassemble with dielectric grease. This stops future corrosion, and sometimes you just get a lose connection, and pulling apart/putting back together makes the connection come back.

3) Check for spark on each plug wire.

4a) If you lose spark on 1/4 or 2/5 or 3/6... then look at the trigger.
4b) If you lose spark on 1/2/3 or 4/5/6 then look at a lose connection on the charge wires.
4c) Reflecting above... if you did loose 2 and 3, but 1 is firing, then the charge diode in #1 may be bad. (they balance each other) Then, check the coil/CDI's.

 

[Jace LaValle]

The corrosion goes a lot further down the wire than I originally expected. I got heat shrink tubing and will be repairing the wires today.

 

[Jace LaValle]

Re did the wiring and harness from the trigger and still having the same problems.

 

[Jace LaValle]

I think I've discovered the problem... hopefully.. I discovered today that the "spark advance of the trigger was not moving underneath the flywheel when the throttle was moved. I'm thinking either my spark advance screw or primary pickup screw cam loose at some point and threw off the timing. Will be re-timing the engine tomorrow. Do you think this could be what is causing my problems?

 

[Dr Honda]

Well... it won't help, and it needs fixed. But, those 2 relatively clean pugs, is telling me it's not firing at all on those cyl's.

 

[Jace LaValle]

Okay new trigger is in. Spark on all cylinders. But it cranks and doesn't start. Made sure battery was fully charged but it dropped from 100% to 50% after trying to start once. Is this indicting a battery that needs replaced?