Engine running rough, low power, high rpms

[Mark E. Barnes]

Bought my 212x in October. Ran perfectly on our test drive--lots of power, no issues.
Parked in garage over the winter and took it out for the first time yesterday and had a few engine problems. This is my first jet boat, so I would appreciate any suggestions you have.
It was stored in our garage with about a 1/2 tank of gas but I forgot to add the fuel stabilizer to the tank. So maybe the gas has gone bad, and is affecting the performance? Previous owner used it very little last summer and it has a 50 gallon tank, so the gas could be up to a year old.

Here’s what was happening yesterday:
-Overall, low power, especially when pulling a skier up—really weak ‘out of the hole’.
-RPMs on each engine were very inconsistent. One side would sore up to 10-11,000 rpms whole the other was at 6-7,000rmps
-engine felt “rough” at times, shaking a bit and less power.

I hosed out and replaced the impeller plugs before we left so they are cleaned out, unless we picked up something yesterday.

I am considering the following:
1. Spark plugs
2. Bad gas
3. Fuel filter
Other ideas?

Thanks everyone,
Mark

 

[Revo]

October until now is quite a long time, especially if you stored it half full with no additives AND didn't top off before running.

That said, if it was fuel, I feel it would likely affect both engines similarly - was the engine that lacked RPM always one side or did it seem to go back and forth? If it's one motor I don't feel fuel is the direct cause. It's possible the fuel gummed up the fuel filter or possibly injectors and thus fuel is an indirect cause. If it goes back and forth then I would say it's bad fuel.

I'd definitely start with at least topping the tank off with the highest octane available (91 or 93) and also add an appropriate dose of fuel injector cleaner. At least pull the plugs and inspect. In any case, a fresh set of plugs for both sides is not too much and you can always keep the old plugs as backups if they turn out not to be the cause of your issues.

I learned the hard way not storing properly on my Seadoo. Did the exact same thing you did - half a tank, no stabilizer, just threw it in the water next season about 6 months later. It started up just fine and idled fine out through the no wake zone. As soon as I started applying power under load it sputtered and was dropping cylinders and if it wasn't for electronically controlled idle it would have stalled on me. I idled it back in with it running on 1 cylinder and shaking like crazy. Drained the gas and replaced with fresh plus 1 bottle of fuel injector cleaner and put in brand new plugs and she ran like a champ. Now I always add stabilizer and top off before the end of the season.

 

[Mark E. Barnes]

Thanks, Revo. Great suggestions. I also really liked your idea about the spark plugs--replace them now so I can for sure eliminate them as the problem and if they are fine, keep them as a back up. And it will be a good chance for me to learn how to replace them!

The rpm and performance problems were inconsistent and back and forth between both engines. One would rev high, the other stay even and vice versa, so I am leaning toward the fuel as the problem. Also, I talked to the previous owner yesterday and he said they hardly used the boat last summer so the gas could be from a year ago or more!

Today, I was planning to syphon out a small amount from the bottom of the tank and see if it looks bad or not. It is a 50 gallon tank and gauge shows a little under 1/2 so I am estimating I have about 20 gallons in the tank. Should I try to pump/syphon that out and put it into my Suburban gas tank? A couple other people said that while "bad gas" like this negatively effects a boat engine, it would not hurt a V8 Chevy engine. (If not, then I don't know what to do with 20 gallons of gas I drain out of the boat.)

I really appreciate your ideas.

Mark

 

[Revo]

Since the issue generally affected both engines, I would also put my money on fuel, especially given the additional information provided by the previous owner.

If it’s convenient for you to siphon out, I would do so. Watercraft fuel tanks typically hold a rather large reserve so if you show roughly half a tank I’d bet you have closer to 30 gallons in there.

How aggressively an engine is tuned will influence how much they are affected by fuel. Typically Chevy small blocks in their SUVs and trucks are very under stressed and thus they can cope better with poor quality fuel. It’s not a gaurantee and I would do my best to drive your car easy while burning that older gas. Will certainly fare better than the high RPM and more performance oriented engines in the boat.

Make sure you use a torque wrench so you don’t over tighten the spark plugs. Spark plugs are easy but you need to pay attention to the details when doing them. New spark plugs will have a washer that gets compressed so it’ll take an extra turn or so once there’s resistance before they reach torque. Used spark plugs being put back in will not have this so they’ll torque almost immediately after being threaded in. Also don’t forget anti seize.

Regardless, I’d still add a healthy dose of fuel injector cleaner to your tank when filling up. When I say healthy, I mean if you buy a bottle that says “1 bottle treats 10-20 gallons” then you’ll want 5 bottles for 50 gallons. Err on the higher concentration dosage.

 

[the MfM]

...

 

[Mark E. Barnes]

Update:
Checked one spark plug and it looked good. And since it was running perfectly in September and then parked in garage all winter, I would be surprised if my problem was spark plugs.
I also checked those large impeller access port caps and found that one was loose. I had placed them before going out, and tugged hard, but I guess not hard enough and one popped out. I am sure that caused the worst of my performance problems! So I am think that and possibly the old fuel are the main issues. I will also test the gas for water and then syphon out the fuel and start with a fresh tank if it looks bad.

 

[Revo]

Fuel sloshing causing air in the lines would require seriously rough water. I can see it happening if he was near empty but with almost half a tank it seems very unlikely to me.

Stabil is fine for preventing fuel degradation but it doesn’t clean anything. You need fuel injector cleaner for that.


Mark, if you’re sure it’s fuel you could just try topping the tank off with 91 or 93 and a good dose of fuel injector cleaner and just run it. If it runs well enough at partial throttle just burn down as much fuel as possible and then top off again with 91 or 93. It’ll probably be fine by then.

 

[the MfM]

Deleted to avoid confusion...

Misread what boat OP had.

 

[Mark E. Barnes]

I will definitely pick up some of the fuel injector cleaner.

Do you think that since I found the loose impeller port cap/plug part that I should test drive the boat now, before the hassle and expense of removing all of the fuel? Or maybe add the fuel injector cleaner and top off the tank. (Although if I top it off and still decide I need to drain the gas tank, then I am dealing with 50 gallons of gas, rather than 20-30 now.) I will take it for another test run today--with that plug properly inserted, and see how it performs.

 

[Scottintexas]

if you had a loose/uninstalled cleanout plug that would definitely cause you loss of thrust issues,

I would consider a set of cobra EZ locks, if those plugs ever "blow" while underway they can break your hatch, it's cheap insurance to help confirm they are installed correctly.

if you're near the water I would test drive it again and see if symptoms are the same,

.

 

[buckbuck]

And I highly recommend you buy the EZ-Locks. I got a call from a member Saturday with a 212X that blew a plug and narrowly avoided water in the air intake which would potentially trashed his engines. Do not rely on Yamaha's plug design to stay in by its self.

 

[Mark E. Barnes]

Thank you for the suggestions about the EZ Locks. I will look into those tomorrow, along with Trulocks and the Purple Plug Fix. I took my 212x out again today after re-setting the plug in place and my boat's performance was much better on the lake today. HOWEVER, each plug blew out at one point on our trip and each took considerable time, effort, and a sore back to get them reinstalled. They were super hard to push down far enough into place. I thought they were in tight but I guess not tight enough. Maybe they are worn out on my 2008 boat? I tugged on them really hard to ensure they weren't loose, but they still each blew today. Thankfully they didn't damage anthing because they stayed jammed in the hole. On one side, the whole shaft area was full of water. Is that an indication the plug is not in tight enough--if water is filling up that whole shaft?

With the Cobra EZ locks, do they ensure that they are seated far enough down in there, in order to work? Meaning, they won't fit into place and appear locked, but not really be in far enough--like my plugs were today?

 

[sunbyrned]

This video explains how EZLocks work. After having to buy a new engine due to a blown plug, I won’t go without them. By the way, if your plugs are getting dislodged in the tubing, check to make sure the tubing hasn’t been manipulated and leaving a gap between the tube and the hole opening. It should be secured to the lip of the hole with a hose clamp, which you can access from the removable hatch cover where your plugs are located.

 

[buckbuck]

@Mark E. Barnes
Do not assume that you incorrectly installed your plugs. The plug design will come unlocked by itself.

The EZ Locks will not engage unless the plug is inserted correctly and locked in place. You will get an audible and visual confirmation when they are locked. And just a note; the Yamaha plugs will possibly continue to come unlocked as you boat. But you will not realize it because the EZ Locks will keep them from moving. Only at the end of the day will you discover the plugs came unlocked when you have to push the plunger down to remove the EZ Locks.

I would suggest you do not use your boat until you get these installed. You are risking a very expensive repair if the plugs are letting loose on a regular basis.

Post some close up pictures of your plugs. Especially the ears that extend out.

 

[Mark E. Barnes]

Here are pictures of plugs, close up on the “dogs”. They are dirty and scuffed but seem structurally sound. After I took them out for winter storage, I am thinking I just didn’t get them inserted far enough, and/or boat jostling like the EZ Locks owner talks about in his video. I will add the EZ locks and reset them carefully. the

 

[Mark E. Barnes]

Thanks again to everyone who has helped me—a rookie jet boat owner.
I just had great success with the plugs. Took them out, cleaned them, and sprayed them with all purpose silicone spray. They slid back in WAY better and clearly much farther down. I am sure now that I did not have them inserted properly before. Now they are for sure in the notches and are way more solid—no give at all when I tugged on them. And I will order the EZ Locks for extra “insurance”.
Thanks again!

 

[buckbuck]

That's good news @Mark E. Barnes . Keep after them with the silicone and keep the aluminum tube they drop in clean. Go enjoy the boat with the family.