Engine Performance Issue, please help!

[Thomas Smith]

Ok, I am at a loss with this one here is the scenario.............

Have used my boat multiple times the past several weeks, just returned from a trip on the Columbia River ran it lots and lots with no issues. Spark Plugs changed, oil changed (and changed correctly). I am the original owner of the boat owned it new since 2006.

So, ran it most of the day cruising out on the water, heading back to the ramp cruising at aprox 7000 RPM both engines then a very sudden loss of performance with sporadic RPMs noted on the tach's.

Shut down and went to the clean outs.....acted as if I picked up some seaweed or something. Clean outs are good to go nothing in them.

Tried to refire and the port was very hard to start, acted fuel starved......the starboard fired right up, confirmed no warning lights and confirmed water moving through the cooling system.

Tried to go forward again with both throttles smooth increase and both began to show sporadic rpm's again. Ultimately ended up shutting down the port engine and limping in, the starboard engine ran well without the port running and also would show smooth RPM's when giving throttle......of course this was at a stop due to the other engine being shut down.

Seems like when both are fired up and given throttle they act like they are fuel starved. When only the starboard is running it runs fine......but again unable to test under full load due to no clamps to clamp water intake of shut down engine.


Any ideas??? Ground, Fuel Filter, Fuel Pump etc ??

Thanks as always !!

 

[Bruce]

How old is the battery? Have you tested it? Several owners have had similar issues when they had week batteries.

 

[Thomas Smith]

Honestly, I don't know for sure but I really don't think it is that old.

I will check that and the grounds today, probably the easiest place to start..........

 

[Scottintexas]

When was the last time you fueled up, is it always a the same place, maybe you have some water in fuel.

I believe your fuel sender is easy to access or maybe you could disconnect it at the engine to pump some out or siphon it from the sender.

 

[Thomas Smith]

I fuel up all over the place, didn't think of water in the fuel I can check that too........I hope to start tearing into it this week

Have any of you ever installed a fuel filter/water separator? Was going to look at that addition as well.

 

[Scottintexas]

check this thread out for both fuel/water filter and his problems with water in the tank,
https://jetboaters.net/threads/busy-couple-of-weeks-eight-projects-completed.9012/#post-154787

If you pull some fuel from the sender spot make sure you pull from the bottom, we had another member that looked down and with the white ish background of the tank thought the fuel looked clear but it was actually the water/fuel mix layer he was seeing and not the bottom of the tank.

the thread should also give instruction about activating the fuel pump to help empty the tank,

 

[Thomas Smith]

Nice !! Thank you

 

[Thomas Smith]

Also, I have not torn into this project yet but...........some say the kill switches but I find it odd hat while sitting in flat water the port engine not only started rough but idled rough and was not smooth........I figure the switch would have to be directly related to "rough" or bouncing along to jar the connection ...........any thoughts?

 

[Scottintexas]

I would agree that kill switches are probably lower on the list but they are easy items to check (once you remove the clean out tray cover).

I think you're just in the trouble shooting phase over eliminating the easy stuff that we all have seen do crazy things, battery connections, kill switches, fuel tank, etc..

 

[Thomas Smith]

Finally getting after it...........here is an update

Also, I went ahead and replaced the battery, then the plugs and also was attempting to get the deck up in order to replace the fuel pump but I have three screws giving me trouble. So that is delayed, I did purchase a Quantum Fuel Pump,

http://www.highflowfuel.com/i-23899890- ... -2015.html

After changing the battery and the plugs, both engines seem to run fine, a little bouncy at low RPM (between 100 and 200 RPM variables) They would rev up nicely and did not sputter or even stall out like before. I am a bit concerned since this is on my trailer and not in the water with a load placed on the engines.

Annually I change the plugs and this time I felt they looked like crap compared to years past. I have attached a photo.........So more to follow on this and if you have any input that would be great.

 

[Stuntmanmike]

Can you take a pic of the center/or inside, That will tell you how much fuel your burning among other things.

 

[jdonalds]

Wow those plugs are really messed up. There is no reason they should look like that. Somehow water or other liquid is getting into the plug tunnels. The tips of my plugs and the white ceramic is always brown after a year, but the upper part of the plug, above the threads, always looks like new.

Do you have any idea how all of that rust/corrosion was formed on the plugs? One thought is using old compression gaskets.

 

[scokill]

Wow those plugs are really messed up. There is no reason they should look like that. Somehow water or other liquid is getting into the plug tunnels. The tips of my plugs and the white ceramic is always brown after a year, but the upper part of the plug, above the threads, always looks like new.

Do you have any idea how all of that rust/corrosion was formed on the plugs? One thought is using old compression gaskets.

I was gonna say the same thing. Mine pretty much look brand new when I change them. I change them every year though. How long were those plugs in?

 

[Thomas Smith]

Well, I checked my records, (which I am usually pretty meticulous about) and I do not see where I changed them last season.....So they might be two season old........I always use the new compression gaskets....I have included some pictures of the Port and Starboard Plugs.."S" "P" in the photo. The port which is the engine giving me the most trouble is a lot darker for sure. Thoughts on this?....

 

[Stuntmanmike]

Your A/F mixture looks ok, But the port side plugs look worn out. A freash set should make a big differance.

 

[Thomas Smith]

Do you think being worn out would cause rough running while cruising at 7000 RPM's or just low RPM's.......? Thank you

 

[Stuntmanmike]

A bad or fouling plug will cut out when ever it wants, That's why new plugs are the first on the replacement list when you start having running issues. Pedal to the metal!

 

[Thomas Smith]

Well, I am going to be a happy camper if when I get this thing out on the water and thats all it was...............

 

[jdonalds]

Changing the spark plugs has long been a fix for most Yamaha engine issues on these forums.

I repeat though that your plugs look quite out of the ordinary. I've never seen plugs like that. Something else is going on.

 

[Julian]

I'm a little late to the party here but my first thought would have been plugs! I had very similar symptoms with my 2005 SX and went through a number of days of head scratching until someone said...have you changed the plugs. Mine were only 6 months old...but that was the problem! Let us know how it turns out.