Engine not starting, knocking

[Gator6]

cou2006 Yamaha SX210 (the previous owner thought it was an AR). I bought it back in June from a guy I worked with and completely trust. I spent 5 years operating/working on combat jet boats for the Navy. We live in Key West, so this boat hasn't seen cold weather in years.

About the middle of July, I was preparing the boat to take the family out for the day. First off, I'm kicking myself in the butt as I've been in the Navy for 18 years, and have suddenly forgotten which is port and which is starboard (which side, I got the lights and rules down). Anyway, I got one engine to fire right up (right side while facing bow), but the left engine (facing bow) would just click, click, click. Eventually, the engine fired up, ran a bit rough, but worked enough to get off the trailer. The same engine would give me the same problem two hours later when getting ready to leave the dock but was a trooper for the rest of the day.

A week later I went to prep the boat for another outing, but that left engine wouldn't start, just click...click...click. I could see the engine jerking, but wouldn't crank. Eventually, my patience wore thin and I fried the starter relay.

So, here we are at the middle of October and I'm just getting to work on it. I replaced the whole starter and relay, but now all I get is this horrible knocking sound, and that is it. It will not even run. I got the opposite engine going first try, a bit rough, but I'll take it.

Is this a plug issue? It sounds like the fuel is fine, I couldn't see the sending unit being bad. Just a bit lost at this point. Thanks in advance!

Casey

 

[Scottintexas]

do you have the MR-1 HO or non-HO engine? what is the displacement?

just spit balling, it could also be your impeller wear ring is swollen and slowing down the engine, you could pull the impeller and try to start the engine, it would also remove a lot of the vibration/noise and help you diagnose the rough sound on the other engine also,

When was the last time the plugs were changed on both engines?

 

[Gator6]

I'm still not that familiar with the engines to tell you that, lol.

 

[Gator6]

My next step will be to change out the plugs since I do not know the last time they were changed.

I took the boat out for six straight weekends without issue or either egine running odd. Just seems odd that it would have cranking issues that evolved into not starting in the span of 6 days, and once the starter and relay were replaced has a new issue.

 

[Scottintexas]

look either inside the cockpit where the engine hatch closes or around the engines for a label/plate that should show your engine info,

If your liner swelled it only takes a minimal amount to cause it to seize,

So the engine never starts, only turns over with a bad knocking sound?
Does it sound like it's spinning at the proper speed?

 

[MidnightRider]

...and have suddenly forgotten which is port and which is starboard

"Left" and "Port" both have 4 letters. How my daddy taught me to remember.

 

[Gator6]

I use to say port short to remember the red light

 

[Gator6]

look either inside the cockpit where the engine hatch closes or around the engines for a label/plate that should show your engine info,

If your liner swelled it only takes a minimal amount to cause it to seize,

So the engine never starts, only turns over with a bad knocking sound?
Does it sound like it's spinning at the proper speed?

It sounds like it’s spinning appropriately.

I’m out with the fam, so I’ll check the engine info tomorrow...unless I have a pic somewhere

 

[Cobra Jet Steering LLC]

I also believe the wear ring has locked up your impeller, the longer the boat sits the more it will swell from dissimilar metals corrosion under the stainless liner.
Remove the pump and I bet the engine will run, When you hear all the racket while operating the boat on the trailer you are hearing the impeller hitting high spots on your pump liner.

 

[Gator6]

Sorry, it's been awhile. I discussed the issue with someone who agrees it was/is a hydro-lock issue (engine jerking when trying to start) it has now had a replaced starter, starter relay, and new plugs.

Sounds like either there's no spark or the injectors are clogged. I have a video, but it will not let me upload from my phone.

 

[Scottintexas]

maybe we have terminology issues, when you say "hydro-lock" most of us use that term when water is forced through the exhaust system into the engine cylinders,

You didn't mention anything about running on one engine above no wake speed or water hose on/engine off or any sort of water intrusion,

I would remove the impeller/shaft, it only takes 20 minutes so you can eliminate the wear ring,

Since the other engine sounds rough I would think fuel contamination issue,
https://jetboaters.net/threads/so-it-doesnt-appear-to-be-the-spark-plugs-need-some-help-here-resolved.7029/page-3




.

 

[Cobra Jet Steering LLC]

Smell the oil if it smells like fuel and the level is high you probably have an issue with an injector. If not remove the spark plugs and crank the engine if it still does the same thing you have a pump locking up.