Pro XS 225 issue

[dwoodfin]

2B361424
2017 Pro XS 225. 340 hours. Yes I use it ALOT
Started noticing a “miss” in my engine back in the spring. Actually thought it was my prop. Changed prop but problem continued. About a month ago took it in to my mechanic who discovered that I had a blown head gasket. Repaired and I thought my “miss” was fixed...it wasn’t. My mechanic drove my boat today and we pinpointed that the problem only occurs at one rpm range, about 4300 to 4800. If you get it up cruising at about 4500 it starts missing until you either back out or increase the throttle. It’s like in that rpm range something is holding it back until you increase the throttle and power through it. I’m gonna leave it with him next week. He said that he wasn’t sure what was going on but mentioned possibly having to do with the throttle position sensor. Said he didn’t think it would be a plug or plug wire with it acting up only in that one rpm range. Anybody seen this issue or any ideas?

[lpugh]

Seen it many times, both autos and outboards, I have also seen alternators with failed diodes create enough AC voltage feeding throughout the system to cause similar symptoms. Though not likely, something to be aware of. A diode/stator test is quick and easy. The time wasted and hair loss can be very costly if you get bit buy bad alternator and you have failed to check it. Every couple of years I see a bad one in autos causing computer related problems while still working well enough to keep the battery maintained.

TPS would be my first test with that symptom, I would also add that if the TPS tested OK with a scanner, I would then test it with a high quality DSO or Lab Scope. It is also possible that the TPS may test good in the shop, but not on the water due to temperature, vibration and harmonics. In such cases it would cost less to replace than diagnose it. It always make us feel a lot better though to confirm a part bad than just LSI (lets see if) it fixes it

[Savage]

Perform a spark test as the problem is occurring.

[dwoodfin]

Still having this issue with motor. Mechanic has had it a couple times but hasn't figured it out. Has ruled out plugs, wires, coils and some other things he says. Says the TPS is performing as it should according to the computer. Supposed to have ran it on the water while on the computer yesterday. Says there are signs that a mouse has been in my cowling and done some chewing. Says he doesn't know if that could be any of the problem anywhere. Getting frustrated!

[Savage]

It's under warranty, so get a Mercury Representative involved in your case.

[EuropeanAM]

First and foremost- make sure ALL recommended maintenance is up to date. This INLCUDES the fuel filter, and fresh, properly gapped NGK- IZFR6J Spark Plugs (must be gapped to .044" and torqued to 20 lbs/ft with a torque wrench).

IF the problem persists after this, and all BASICS check out ok, I would suspect that one of the following COULD be a contributor:

-Reed
-MAP Sensor
-TPS Sensor
-Direct Injector

In the case of the sensors, it may actually be a "failed IN RANGE" scenario, meaning that the easiest way to rule it out is to try a known-good component.

[dwoodfin]

Talked to my mechanic today. Said he thinks it’s the ECM. Said he put a different one on and ran boat and all was good. Put mine back on and ran and the problem returned. Has a call in to the area Mercury rep to tell him his findings. He has been in contact about the problem. Said that he wanted to see how mercury wanted him to proceed with the fix. Don, all maintenance has been done on motor as well as trying new plug wires. Thanks for responses and I’ll let know the outcome.

[Savage]

Good call getting the Rep involved.

[EuropeanAM]

Be sure to report back.

[dwoodfin]

Update...after having to send ecm back to Mercury at their request for a re-flash finally got it back on Monday. This was after they put the wrong return address on package and it ended up on the other side of the country for an extra week. Mechanic ran it yesterday and the problem is still there. Put another ecm off of a 250 on it yesterday (didn't have another 225 ecm handy) and the problem was still there although it moved from 4500 rpm's to 5500 rpm's with the 250 ecm. Said he recorded both runs and there is nothing that shows up on the recordings that he can see that indicates the problem. No drop in voltage, fuel delivery....anything. Talked to the rep last night about the problem and was told to clean the injectors and if that didn't do anything then he would send an entire new fuel rail to put on. Very frustrated, missing the fall bite entirely!

[EuropeanAM]

Just out of curiousity- have the TRIED a known-good TPS and known-good MAP on this engine?

I've seen several that were a real "bear" to see in the data, but were definitely causing a problem. Being that it seems to be centered on one particular area of throttle or "demand" I still suspect the problem is in one of these areas.

[dwoodfin]

I asked the question again last night about the TPS...due to the fact that was what he first mentioned as a cause months ago. He said that it wasn't showing up as a problem?? But neither is a fuel problem showing up but they're talking about replacing the fuel rail? Doesn't make sense but I for sure am not a mechanic. If the rep wants to replace my fuel rail and put all new injectors in...I'm good with that I guess. As long as they find the real problem in the end. Assuming the rail doesn't fix it.

[BASS24-7]

check reeds had a small crack in one on my last boat that i chased around for a while, they thought it was TPS / rails /or plugs

[EuropeanAM]

Rep should find it, or find someone who can.

BTW... it was the Powerhead Gasket (NOT the Cylinder Head Gasket as stated earlier). Big difference.

[dwoodfin]

Don, where did I say cylinder head gasket? Lol..all I see is where I said "head gasket" in the first post. Didn't hear anything yesterday. Hopefully today.

[Savage]

Well the term "head gasket" is the same as "cylinder head gasket" in a technicians world.

"Powerhead gasket" means only one thing....

[dwoodfin]

Gotcha

[EuropeanAM]

It's all good... just good to know which area they were in.

Wonder if they "looked" at the adapter plate gasket while in there (as best they could)...?

[dwoodfin]

No idea Don. Just spoke with mechanic. Said no change after cleaning the injectors. Said the rep texted him today that he was sending some parts. Don't know what parts he's sending.

It's all good... just good to know which area they were in.

Wonder if they "looked" at the adapter plate gasket while in there (as best they could)...?

[EuropeanAM]

Be sure to report back... will be interesting to hear the resolution.