Engine Missing...Suggestions?

[slow007]

A couple weeks ago, I started having intermittent fuel/throttle/engine misfire issues with my 2013 SX190 with 72 hours on it. Sometimes the boat will run like a champ, other times it acts like it is not getting fuel or start missing in one cylinder (can't tell which)...and struggles to even get on plane. It may run great for 10 seconds or 10 minutes, then want to bog down like it isn’t getting fuel. There is no pattern to it. The boat tends to run great for 3-4 minutes after it is launched. The problem seems to be more prevalent on rough water (electrical connection?). It was running great over glassy water then came across some mild wake and it started missing. When not running properly, it will only maintain 6200-6400 rpm.

I have changed the spark plugs, checked the ground connection to the battery, checked the ground at the engine block (that’s a booger to get to), checked the inlet and cleanout for obstructions/debris, checked voltage at the battery, and added Sea Foam to the gas. Oil is at the proper level, the “pee-hole” shoots out water like always, and am not getting any check engine or overheat warnings.

If it was bad gas, I don’t think it would be intermittent. I always run Stabil marine and typically 87 octane from Shell (with ethanol) and never had an issue. The gas in the boat is only a couple weeks old.

The issue started after a rough water day on the lake (roughest I’ve ever seen on this particular lake in 20 years). Any thoughts on what else I should check? Ignition coil? Fuel filter/screen? Is it time to take it to the dealer?

 

[Bruce]

Have you checked the air filter? You could run without it for testing.

 

[Julian]

If it was bad gas, I don’t think it would be intermittent.

Not so sure about that....I'd add more seafoam / ethynol stabil treatment and fill her up again. Could be water in the tank at the bottom, and when you are moving more, it gets mixed up better and pulled into the pickups in the tank....

 

[slow007]

Have you checked the air filter? You could run without it for testing.

I took a peak at the air filter but haven't pulled it out for a thorough inspection. I run it without the filter today and see what happens. The Yamaha dealer winterized the boat last fall...I assumed the air filter was part of that service but maybe not. Thanks.

Not so sure about that....I'd add more seafoam / ethynol stabil treatment and fill her up again. Could be water in the tank at the bottom, and when you are moving more, it gets mixed up better and pulled into the pickups in the tank....

I will try air filter first, then fresh gas with additives. Thanks.

 

[Julian]

I assumed the air filter was part of that service but maybe not.

Unlikley they changed the air filter. No dust on the water means air filters rarely need changing the way car filters do.

Another thought is an exhaust leak. We've had boats that died at higher RPMs because of an exhaust leak....the engine effectively was starved for fresh air. This was diagnosed by running the boat with the engine compartment open.

 

[Jgorm]

I'm dealing with something similar on my mr1 ski. Sometimes I get 9500+ rpms, sometimes 9000. It's almost 10mph different. I pulled the coils and it's not running on #3 at idle. It's shooting sparks so I'm going to clean the injector and swap it to a different cylinder.

 

[haknslash]

Any loose or bad connections at the ECU? Any warning messages?

 

[slow007]

My issue ended up being a bad connection at the #2 fuel injector. The dealer fixed it and checked the other three fuel injector connections so ended up only costing a couple hours of labor (which included them taking it out on the water). I took it out yesterday and it ran like new. Thanks to all those who offered input and suggestions.