AR240 one cylinder acting up

[bcage]

I have a 2014 AR240 that has been a great boat. A number of years ago, I noticed that early in the season one or both of the boat engines would not run consistently. When the engine was throttled up it would run, but the RPMs would alternate between a higher level and a lower level. This would be mostly present the first outing and would disappear after a half hour or so on the water. Then, after a few outings, it would disappear altogether for the rest of the season.

I always (naively maybe) attributed it to stale gas or a plugged up fuel injector. As should be obvious, I am not a mechanic, but know just about enough to talk to one.

I was considering trading the boat and the shop tested the motor and said that one of the cylinders was "dead." Basically, said time for a new engine. Obviously didn't trade the boat, but what I treated as a minor annoyance previously, I now want to figure out and resolve. The statement that the cylinder is "dead" doesn't make sense since it comes back to life after a few moments (literally within 90 seconds or so) and then, after a few outings the problem disappears and the boat is fine for the season.

I am curious if anyone has any insight into what might be the cause of this behavior? In my head the fact that it goes away made me think fuel; either stale gas or fuel injectors. It could be spark, but it doesn't seem to align with the fact that it fades away after a period of time, only to show up again the next season. Any ideas, advice?

Thanks

 

[Acard7]

Check the easy things first: oil level, air filter, and when’s the last time you put a new set of spark plugs in?

After that you could probably buy your own compression tester from your local auto parts store, then look up on YouTube how to perform it, it’s not hard! Unless that shop did a compression test and gave you the numbers? If so i’d still do one yourself or get a second opinion since you say the boat runs fine after a bit.

Trying to find YDS software to hook it up and check any stored engine codes would be nice too.

Any other symptoms? Hard to start? No check engine lights?

 

[Cobra Jet Steering LLC]

What cylinder is it number 3 by chance?? or he did not say , do a compression check on the engine write down the number for each cylinder be sure the throttle is OPEN when you are doping it.
You may have a coil connection that is not in good shape and cutting out the spark , you may have some water in the fuel tank, the spark plugs are the report card of the engine so remove them and see what each one looks like and be careful if one gets stuck when removing it stop and spray some wd 40 in the plug recess and then retighten it and then try to remove it and repeat the process until it comes out otherwise you can break off a plug in the head and have a lot more issues to deal with The MR1 engines do have a history of having the exhaust manifold leak water in the combustion chamber due to corrosion.

 

[FSH 210 Sport]

My first thought was coil pack, then I thought spark plugs, now I have to ask, what maintenance has been done and how many hours on the boat.

If the cylinder comes back to life that doesn’t sound like hard parts, that sounds like something electrical?

I’m also curious as to what the shop means by a dead cylinder.

 

[Neutron]

Swap all four coils with the other engine , see if it moves. Are you handy because you can swap injector rail, fuel pumps. Etc one at a time to see if the problem moves.

Wonder what the tech determined what the issue was causing the dead cylinder?

 

[bcage]

Thanks for all the replies. I have asked to get the cylinder number from the shop but I don't have it yet. Like all of you, the fact that it comes back to life makes me think spark or fuel injector. I did have them replace the spark plugs so I will see if that has any impact when I put it back in the water.

I am very handy, but I am no mechanic so my thought process is likely flawed, but the fact that everything comes back to life made me think bad fuel and possibly a plugged injector. Like I said, early in the season when I take it out, it will randomly alter its revs; high and low. It is clearly either on or off, not variable. After a period of time, maybe 15-20 minutes the problem goes away and after a handful of outings the problem disappears for the rest of the season.

That is why I dismissed it as bad stale fuel. I will take it out with the new plugs to see what happens there. If I get the number of the bad cylinder, I will see about swapping out coils and maybe the fuel injector for that cylinder. Is there another way to test the coils? Does this sound like I am on the right path?

Thanks again for all of the suggestions and insight.

 

[Acard7]

Ya, sounds like a good plan. Also take a look at your electrical connectors to the coil pack to that cylinder in question to see if there is any loose wiring or anything that looks out of ordinary compared to others. You can use some electrical contact cleaner on the coil pack wiring plug too and hope that works as well. Swapping out coils would be one of the easiest things to do for sure.

 

[bcage]

No check engine lights, not hard to start. Basically nothing obviously wrong. Oil is good, just had changed along with filters and plugs. I wouldn't think oil would impact, but what do I know.

I just checked the cost for coils and they are not expensive so I am going to replace all 4. I don't know the cylinder number, but I do know it is the starboard engine. I will look into how to do a compression test. Never done that. I will look for loose connectors and spray them down with contact cleaner and give an update when done.

Thanks all!

 

[Acard7]

No check engine lights, not hard to start. Basically nothing obviously wrong. Oil is good, just had changed along with filters and plugs. I wouldn't think oil would impact, but what do I know.

I just checked the cost for coils and they are not expensive so I am going to replace all 4. I don't know the cylinder number, but I do know it is the starboard engine. I will look into how to do a compression test. Never done that. I will look for loose connectors and spray them down with contact cleaner and give an update when done.

Thanks all!

You can save yourself some money by just swapping all the coils from the good engine to the bad engine!! Don't want you to spend too much money throwing parts at it!

 

[BumbleBee255]

I am more fluent in the motorcycle engine department, but these are not that different. When a professional mechanic uses the term "dead cylinder", that would normally mean that the the cylinder in question is not producing anything close to the spec amount of compression. This would be very noticeable in performance/power. A cylinder that is producing low compression (in spec or slightly below) will perform better after it is warm. That is why ALL compression checks that are done in the motorcycle world are done with the engine at operating temp. It also ensures that there is the proper amount of oil on and around the cylinders and piston rings. Previously mentioned before, you need the compression numbers for ALL cylinders from the dealer. If a shop told me that one of my bikes had a "dead cylinder" and it still performed after warming up, well,,,, I would be done with that dealer, or at least that mechanic. Maybe a second opinion from a different dealer will help if you don't want to go thru all the work of testing yourself.

Also, a cylinder with low compression after sitting all winter may increase it's compression after a few outings (because of the oil retained in the rings) for a period of time depending on how long of time between outings. But, if it it truly a low (but in spec) compression cylinder, it will continue to get worse and it will need to be dealt with.