One engine running lower rpm than other at WOT

[Brutus_Tx]

Good day... I just wanted to share my experiences from the weekend and to ask a question.

I have a 2011 AR210 with ~ 100 hrs on the engines and a few weeks ago when out running the boat I noticed that the port engine was running at only 6500rpm at WOT, while the starboard engine was running at 8200 rpm per the gauge. The engine would start first crank and idle smooth, throttle response was immediate and rpm climbed smoothly up until it hit 6500 rpm and stopped.
I scoured Jetboaters.net looking for a solution.
Some threads had me checking the throttle linkage to see it they weren't hitting the stops, but that wasn't my issue.
I then checked the oil and noticed my port engine was about a quart low, while the starboard was at the proper level. So I was losing some oil somewhere.
I added a quart and went back out for a quick run, with no improvement in RPM.
Came back in and checked the air filters... they were clean. Then pulled the intake and noticed oily residue on the throttle body... I cleaned the intake. The other throttle body on the starboard engine was clean. I pulled the spark plugs to inspect them, but they didn't appear too bad to me to be honest. Out of an abundance of caution though, and trying to eliminate all possible issues, I replaced them. I wasn't hopeful to be honest, but when I left the jetty the second time and opened her up... yeehaw! I was back to 8200 rpm on both tachs... so that solved the performance issue.

Now my question.... I'm losing oil somewhere and it appears in may be getting cycled through the throttle body into the engine and slowly fouling the spark plugs. Do we have a PCV system on these engines? Is there a common failure mode I need to be looking for and any parts I need to replace? I really don't want to pull my boat and have it sit at the dealers for a few weeks to replace something I can probably do in a an hour on the boat lift. Any suggestions are greatly appreciated.

I'm just glad its back on the water in prep for the Memorial day weekend coming up...

 

[butch5505tony]

I am having the exact same problem. I have 2012 ar210. I am having a mechanic come out next week.

 

[Seadeals]

Glad plugs worked! Replace plugs, replace plug, replace plugs when it comes to first step with RPM issues. You checked good things but the engines are very sensitive to even good looking plugs. It is annual preventative maintenance. As for the oil, if it was a quart low, I suspect you just now (because of this issue) started looking at it more closely. It may have gotten that way over a long time air due to the sump setup or it may not have been running, warm and level in the water so sump levels varied. Don’t assume an issue. Add then monitor both to see if one drops more than the other. You could do compression checks if you are really worried (losing oil past rings) but my advice is don’t overreact until you log some hours. It’s not like you will run it dry if you are regularly checking oil level.

 

[Brutus_Tx]

Now my starboard engine has a lumpy idle. LOL I'll be changing those plugs tomorrow. If that doesn't work I'll swap coils to see if the issue migrates...

the joys of ownership...

 

[butch5505tony]

Found the problem. When u had the plugs changed last not h, the mechanic did not put one of the ignition coils back on. So now I’m firing in all cylinders.

 

[Brutus_Tx]

Now my starboard engine has a lumpy idle. LOL I'll be changing those plugs tomorrow. If that doesn't work I'll swap coils to see if the issue migrates...

the joys of ownership...

i swapped the spark plugs on the starboard engine and the lumpy idle resolved itself.... I'm coming to the realization that changing spark plugs' resolves all issues... lol.

Lumpy idle? Change Spark Plugs
Reduced RPM? Change Spark Plugs

Under the DIY section I think we can solve a lot of mechanical issues by changing the spark plugs... lol. I now stock a full set as replacement onboard for the next time it hiccups...

 

[Evil Sports]

Had a #4 plug issue this year, that engine was not keeping up. New plugs in both and she's a ripper again.