Loss of Power and Vibrations

[Maine-Basser]

Tournament this morning. Beautiful morning, 68 degree air temp and 80 degree water temp. Riding in my 2019 Ranger Z520C with a 250HP Pro XS Four Stroke on the back. Blast off was at 6:20, second boat out, idled to the end of the no wake zone (about 3 minutes of idle time) and took off. Ran the creek, about 1.5 miles, at 45 - 50 MPH. When I reached the main river I depressed the hotfoot and the max speed achievable was 52 MPH around 5000 RPM, normally she runs 71/72 MPH at 6000 RPM. Pulled off to the side of the river and let all the other anglers pass me, engine was idling rough so I shut down for a couple minutes. Engine started back up fine, but was vibrating pretty bad, so we limped back to the marine with a shaking motor (no longer just vibrating) and a top speed of 6 to 8 MPH (hot foot completely depressed). Any ideas before I make the 4 hour trek to the dealer?

[howieranger]

I had a similar thing happen a couple of weeks ago. My wife backed me in and while the motor warmed up she parked the truck and I picked her up off the dock. After idling past the no wake bouys got on plane no problem and ran down lake at 45-50 for maybe 5 minuets and then went to accelerate and could only gain a couple of MPH at WOT. I shut down and started checking things and could find nothing amiss, no codes on the Merc Monitor. I idled back to the ramp with a very rough erratic idle, probably 30 minuets. I pulled the fuel filters thinking of fuel starvation but everything was clean. The next afternoon I took it by my dealer and the first thing he said it was probably the TPS and he'd had one in stock. With the laptop hooked up the throttle load always went to 100% with the nHot Foot at WOT but the reading was always different on returning to idle whether letting off fast or slowly. He adjusted the throttle cable at the motor because it had gotten a little slack and we rechecked and the idle consistently returned to the same reading. That evening the motor ran just fine. I have about 90 hours on the motor so the assumption is that the throttle cable may of stretched a tiny bit. From pulling the cowl to putting it on took maybe 20 minuets.

[Maine-Basser]

Quick update... took the cowling off and looked around. Everything looked normal except there is a thin black line with a small red tip laying in the bottom of the cowling. Any ideas what it is for?

[EuropeanAM]

That's the pitot (analog speedo) tubing. Not likely related.

Did you receive any warning notices via the Warning Horn or Smartcraft?

How recently had you purchased FUEL? Bad fuel (or even water) are possibilities.

[Maine-Basser]

Update: To answer your questions Don; No Alarms ever or Smart Craft Gauge Alerts (only 44 hours on the engine though) since I took possession 1.5 years ago (brand new purchase). I put 15 gallons of gas in on the way to the ramp that morning from the same gas station I have been using for over 12 years.
Boat is at the dealer; hooked up to the computer and engine checked good. There were 6 saved faults on the engine; 5 of them with 0.0 h or 0.1 h Runtime; so assumed these were during rigging. 1 fault at 32 hours, Code Description "Emergency Stop", Type Description "A particular state or condition exists", Enginestate "Stall"; although I do not recall the engine ever stalling.
Mechanic did observe the engine vibrating abnormally, so he started investigating. Found 3 of 8 spark plugs fouled very bad, the other 5 looked perfect. Replaced the 3 bad plugs and started the engine again and it started and idled perfectly. Now he is going to try and figure out why three plugs were so fouled with only 44 hours on the engine and the other 5 looked perfect.

[EuropeanAM]

Run history is likely going to provide information on why those particular plugs were fouled. Another item that's recently been circulated to dealers is that it is critical that the engine be left with a little bit of positive trim when parked (not full down/tucked in). This helps to prevent oil from making it's way past piston rings and into the combustion chamber (causing a short puff of smoke after startup).

Plug inspection at 1 year is recommended (replacement as necessary). In a case like this- I'd simply replace them all (not just 3 of them).

The faults listed are normal... the first 5 from PCM programming, the latter "Emergency Stop" simply indicates that one of the following occurred:

-Lanyard was pulled (intentionally or accidentally)

-Key was turned to the START position while the engine was already running.

[Northwoodswalleye]

Run history is likely going to provide information on why those particular plugs were fouled. Another item that's recently been circulated to dealers is that it is critical that the engine be left with a little bit of positive trim when parked (not full down/tucked in). This helps to prevent oil from making it's way past piston rings and into the combustion chamber (causing a short puff of smoke after startup).

Plug inspection at 1 year is recommended (replacement as necessary). In a case like this- I'd simply replace them all (not just 3 of them).

The faults listed are normal... the first 5 from PCM programming, the latter "Emergency Stop" simply indicates that one of the following occurred:

-Lanyard was pulled (intentionally or accidentally)

-Key was turned to the START position while the engine was already running.

how much positive trim? My boat lift is very shallow so my motor usually sits at 75-90 degrees. 250 hours no smoke on startup or plug fouling so it must be ok?

[ourflat]

[EuropeanAM]

how much positive trim? My boat lift is very shallow so my motor usually sits at 75-90 degrees. 250 hours no smoke on startup or plug fouling so it must be ok?

That's way up there. Approximately 25-30 degrees of tilt (slightly beyond the "trim" range).