Honda 2006 RPM problem

Hi Guys, I am in need of your assistance.
The other day while running my motor on the water, it started to drop RPMs and then jump back up, then drop down and up again the entire time. I could reach high RPMs, but it stil would drop down and back up again. At idle it did sound like it had a miss. So I removed the spark plugs and 5 plugs had a tan color, as seen in the first pic. When I removed No. 6 cylinder plug it looked like what is shown in the second pic.
I changed the coil from No. 6 to another cylinder and the problem was still there.
Could it be a bad coil? Is there a way to test the coil with a meter?
Any ideas would be greatly appreciated. Thanks

I forgot to mention that my motor is a 2006 BF 225 and I did swap out the bad plug and still had problem with RPMs.

Did you actually use a new plug and coil in the swap out or move them to another cylinder? If the latter, replace with a known good plug and coil. You could just be moving the problem around to another cylinder.

Did you try to pull fault codes? A failing plug or coil should give you a "1" fault code.

Thank you for the quick reply.
I did replace plug with a known good one, but don't have another coil, and just moved to another cylinder. I did not get any alarms, but will try pulling codes now.

FYI, I did replace my vapor separator last week with a new one. Boat ran fine first time out after the exchange, but this problem started during the second time out.

Just pulled codes and there was a code indicating a code 1.

Since a code 1 can refer to a bad spark plug or a defective coil, I am thinking it is a bad coil. The O2 sensor was replaced about a 1 1/2 years ago when I did SB# 56.
What are your thoughts?

You said "Boat ran fine first time out after the exchange."

That's good news. It indicates that you probably don't have a compression issue.

See if you can get a spare coil and try that. It's always good to have a spare anyway.

If replacement coil doesn't clean it up, then I would pull the VST again and make sure that your float and float valve are set correctly and working correctly. And clean it out again. There could have been junk down stream in the fuel line that got into the VST.

Also, try to test the fuel pressure. It should be between 41 and 49 psi. You'll need a 6 mm adapter for your fuel pressure gauge. It screws into the pressure relief bolt that is on the cover to the HP fuel filter. If fuel pressure is too high, you will need to pull and clean the pressure regulator.

BTW - when was the last time you changed the HP fuel filter?

One other long shot thought, which happened to me once - after changing out the high pressure fuel filter, I failed to re-attach the vacuum line to the IAB diaphragm, which sits in front of the HP fuel filter cover. My engine got pretty crappy at over 4000 rpm. You might want to check that.

I am going to order a new coil.
I will check the fuel pressure and I changed all filters this season like in April. I did drain the VST the other day and the at the bottom of the jar there were some small white particles settled on the bottom. Should I drain it again until there is nothing present?
And I did reconnect the vacuum line to the IAB diaphragm
thanks again

OK on a new coil.

Yes, I would at least drain the VST again. I know it's a PITA, but if I were dealing with more sediment from the VST, I would consider removing the VST again and checking the float and float valve, and especially the float valve seat. It must be super clean. With the VST off, put the input fuel line in a large clear jar and pump the primer bulb to see if there is any more junk in the fuel line. If so, you are going to need to back up and see where it is coming from. Any sediment from the fuel tank should be caught in the low pressure fuel filter.

Here is what I did as per your advice.

Installed new coil on No. 6
Drained the VST via drain tube............had a little more minute sediment come out
Disconnected fuel line from fuel filter and pumped primer bulb to see if any sediment was coming from fuel tank. There was none.
Cleared codes from Eprom
Started engine and it ran much better, a drop in rpm's @2-3 tenths. Seemed to be getting better the longer it ran.
Checked for any codes again ,,,,,,,,,,,,none

I will try to do a sea trial maybe tomorrow, if it still has problem, will do as you suggested and remove VST to check float and clean really good.
Is it possible that the rubber fuel lines have some build up on the inside and by me bending them to remove the old VST, it caused this build up to loosen up ?

Chawk man, you have been such a big help to me, figuring out problems with my motor, I can't Thank You enough.

Your question on old fuel lines, yes with age they can break down, how old are they? If old, wouldn’t hurt to change the fuels lines from tank to the outboard.

I appreciate the good vibes. Just remember, I am not a trained marine mechanic - just an interested owner who likes to do my own maintenance and repair.

Let us know how the sea trial goes.

Agree with NSDON on the fuel lines.

As an aside, if you don't have an external fuel/water separator/filter (e.g. Racor) installed in the fuel line coming out of the tank, I strongly recommend that you install one. It's an easy DIY project. That alone will catch most things coming out of your tank and keep the fuel system much cleaner. Install it in a way that makes it easy to get to and drain, and drain out a few ounces of fuel/water after every fill up.

And as I have said many times based on my own experience, change out that high pressure fuel filter every 100 hours or every season, which ever comes first. It's the weakest part of the whole fuel system.

My boat is a 2006 Pro line 25 WA, so the fuel lines are 13 yrs old, will make the change of them my next project.
I do have a water/fuel separator installed and drain it occasionally during the season and install new filter once a year.

There is a small craft warning out today, so will make sea trial on next good day.

I am thinking of installing a 1 1/2 " permanent fuel pressure gauge made by Russel down by the pressure relief bolt, using this adaptor.
Is this a good idea?

Took the boat out for a sea trial this morning in Tangier Sound and the motor ran great, best since I bought it, 2 years ago.

This site is the best

That's great news. Must have been a fun ride - over here on the lower Potomac it was rockin and rollin since early this morning. Still is. I have 3 ft. white caps breaking on my sea wall. I guess you had some blockage of this SE wind on Tangier Sound.

As for installing a fuel pressure gauge - I'm not sure why. I see no real benefit of monitoring fuel pressure in real time. You might be better off installing either a water pressure gauge or one or two heat gauges. If you want a write up on installing the heat gauges, send an e-mail to me at [email protected].

The wind must have been blocked like you said, wasn't that bad, choppy. Even managed to catch a couple of rocks.
I will send you an email about heat gauge, thanks

Roger that on the rock fish. Good for ya!

Here on the Lower Potomac we've had the worst rock season in 20 years. Salinity is very, very low. The netters are catching 5 - 10 lb. catfish in their nets. They are so plentiful that they are getting only 25 cents a pound. No croakers to be seen anywhere. I'll likely need to run to your side of the Bay to get to the blues and Spanish this summer, just like I had to do last year.

Pretty much the same here. Went out yesterday, couldn't find any rocks, but I did get a late start. I tried my usual spots with no success, started searching for new locations, trying all the points that had a decent rip. The other day fished what is now left of Pry Island, at high tide it is totally under water, on the outgoing. Good luck, tight lines.