MR1 engine not running more than 6,000 RPM at times

[Konnie]

So I have a 2006 AR230
Don’t use it all that often anymore.
Last weekend when we went for a ride and the port side engine would not rev above 6K rpm for the first hour of the trip.
At times it reved up to the equal rpm of its twin, starboard energize, for a few seconds and then cut back down to 6K. The twin was running at 8K RPM.
The port engine ran fine between idle and 6K but not above 6K regardless of giving full throdle except for a few sporadic seconds now and then when it reved up to the equal of the twin.
But after a hour the the port engine started to run just fine at all rpm levels.
We stopped for lunch for about a hour and a half. Both engine ran just fine after lunch as well.
Any ide what the issue may be with the port side engine? Something similar happened the time before last time as well. But that was the first time it happened.
Regards

 

[Jores]

These engines are sensitive to spark plugs- I'd start by changing them.

 

[mark_m]

So I have a 2006 AR230
Don’t use it all that often anymore.
Last weekend when we went for a ride and the port side engine would not rev above 6K rpm for the first hour of the trip.
At times it reved up to the equal rpm of its twin, starboard energize, for a few seconds and then cut back down to 6K. The twin was running at 8K RPM.
The port engine ran fine between idle and 6K but not above 6K regardless of giving full throdle except for a few sporadic seconds now and then when it reved up to the equal of the twin.
But after a hour the the port engine started to run just fine at all rpm levels.
We stopped for lunch for about a hour and a half. Both engine ran just fine after lunch as well.
Any ide what the issue may be with the port side engine? Something similar happened the time before last time as well. But that was the first time it happened.
Regards

Make sure the coils are all seated properly on the plugs. I did a spark plug change and forgot to plug in a coil. That’s where I’ve seen the mr-1 fail to rev to full 10k.

 

[steveinmd]

Most failure to reach xxxxx rpm is due to a dead cylinder, from spark plug or coil.

 

[Konnie]

These engines are sensitive to spark plugs- I'd start by changing them.

I will do that, thanks!

 

[Konnie]

Make sure the coils are all seated properly on the plugs. I did a spark plug change and forgot to plug in a coil. That’s where I’ve seen the mr-1 fail to rev to full 10k.

Thanks!!

 

[Cambo]

Post results please

 

[Konnie]

Will do!

 

[Konnie]

So I replaced the spark plugs on the port side engine. Plug #3 was tight but manage to remove it. Did use antI-seize when I replaced them about 3 years ago but still was a problem and appears to be a re-occurring issue with the #3 plug on these engines.
Started port side engine and all seams find, we will see if it will run consistently above 6K rpm, which is what it didn’t do before, next time I put it in the water and take it for a ride.

So I started to replace the plugs on the starboard side engine while I was at it. Plug 1, 2 and 4 came up with no problems but I sheard #3 plug off!!!
It broke off just above the treads. Porcelain parts still inside the threads which is still stuck in the cylinder head.

My plan of actions are:
1. Spray penetrant on top of what is left of the plug and let sit for a day or so.
2. Carefully try to pry / pick out the remaining porcelain inside the threads with small screw driver, tweezers and shop vac with small nozzle.
3. Attempt to remove what is left of the plug with help of “easy out” tool. Potentially use refrigerant to cool plug in an attempt to make it shrink and allow penetrant in the threads.
4. If plug successfully removed vacuum out inside the cylinder with small hose connected to shop vac.
5. Insert small magnet inside cylinder to remove and small particles.
6. Apply anti-seize grease and install new plug.

Any thoughts, recommendations and warnings are much welcomed

 

[Bruce]

I think I would just pull the head then remove the stuck spark plug to make sure nothing gets into the cylinder.

 

[steveinmd]

Prepping to do plug change on my buddy's 2004. Googled spark plug break removal. First link recommends a square style easy out due to reduced chances of expanding the slug

 

[Konnie]

Update:

1. Mixed ATF and acetone, dropped in an ounce around the stuck plug to act as a penetrant and lubricant, allowed to sit for a week.
2. With help of a long flat head screw driver that I sharpened to a smaller head with a grinder I managed to grind and break up the porcelain in the stuck plug. As I was grinding and breaking up the porcelin I stoped now and then and used shop vac with taped on smaller tube that sucked up the porcelain debris.
3. I managed to unscrew the stuck plug with help of a conical easy out. I do believe a square one would have been better but the conical one worked.
4. I ordered an endoscope camera from Amazon for about 60 bucs. Looked into cylider with help of the camera and did see some small percelain debris.
5. Added on a smaller flexible tube to the shop vac and inserted it into the cylinder and tried to vacuum up the debris as best as I could. Inspected again with camera and still saw some debris. Repeated the vacuum and inspecting for about 3 hours. Still a small spec I couldn’t get out.
6. Used compressed air and blew out the cylinder through the spark plug hole. Was exhausted, Did not inspect with the camera again.
7. Installed the new plug, started the engine, all sounded good.
8. Toke the boat on a two hour ride. All worked find.
9. Port side engine reved up past 6,000 RPM with no problems. Issued solved!! Thanks for the help!!!

Was this the right approach to remove a stuck plug?
To me, Yes, on a 2006 boat that isn’t many yers from end of life.
For a newer boat, No. I would have had the head removed to make 100% sure that no debris is left.

 

[Konnie]

So during a boat trip the past weekend the original problem re-occurred, the port side engine wouldn’t rev above 6K. Only happened for about 15 min or so, then ran fine. And the following day when I started the engine it really struggled to re-strart. The starter was turning the engine over just fine but it wouldn’t fire properly and start until after many attempts, The engine had not be running for 24 hours so completely cool. The twin started right up with no problems.
Suspect the occasional max 6K rev issue and starting issue are related.
Thoughts?

 

[Dixemon]

Coil pack? Injector clogged?

 

[dgfreeze]

Check your oil for gasoline, just to make sure you don’t a bad ECU intermittently holding an injector open, causing the hard start/bad running issue. It’s a known issue for our vintage, for there to be some water ingestion that damages the ECU, which leads to an injector being stuck open. Worst case scenario, it’s not impossible for this to cause hydro locking on a cylinder, which can snap a connecting rod, or a variety of other catastrophic failures. Not likely, but possible. You can also swap ECU’s to see if the problem follows the ECU, or stays with the engine.

 

[Konnie]

Any suggestions for how to determine if the ECU is bad other than swapping the two ECUs and wait for the issue to re-appear?
Planing on getting the YDS and associated cables.

 

[dgfreeze]

Swapping ECU's is the normal route for diagnostics on that, but if you take the ECU of the bad engine out, you can open it up and inspect it for moisture. If you've got moisture in there, I'd presume it's the problem. You can do other static tests using the YDS, but to my knowledge, the ECU test is definitely the most definitive test for a faulty ECU. If someone else knows of a better way, hopefully they chime in...

 

[Babin Farms]

Did you check to see if the engine is overfilled with oil due to a injector staying open? Do you have any wet spark plugs after it runs? I just went through this issue and had to have the ECU repaired. RPM's off, not starting as easy as before and exhaust/engine sounded slightly different. The best way to diagnose is to swap the ECU's. You will be able to tell instantly if the problem stays with the engine or follows the ECU. No need to put it in the water to test, just run it on the trailer.

 

[Konnie]

Did you check to see if the engine is overfilled with oil due to a injector staying open? Do you have any wet spark plugs after it runs? I just went through this issue and had to have the ECU repaired. RPM's off, not starting as easy as before and exhaust/engine sounded slightly different. The best way to diagnose is to swap the ECU's. You will be able to tell instantly if the problem stays with the engine or follows the ECU. No need to put it in the water to test, just run it on the trailer.

I changed the oil after I started to have the issue with the RPM and starting issues. Also replaced the plugs. Amount of oil I pulled out was consistent with the twin engine and plugs weren’t wet.
I will swap the ECU’s and see what happens.
My only hesitation is that the issue is intermittent. Does not always happen. I may have to leave the ECU swapped for a while until the issue reapers. Where did you have your ECU repaired?

 

[Babin Farms]

I changed the oil after I started to have the issue with the RPM and starting issues. Also replaced the plugs. Amount of oil I pulled out was consistent with the twin engine and plugs weren’t wet.
I will swap the ECU’s and see what happens.
My only hesitation is that the issue is intermittent. Does not always happen. I may have to leave the ECU swapped for a while until the issue reapers. Where did you have your ECU repaired?

https://jetboaters.net/threads/mr1-issues.38022/#post-608641