2002 Launch SSV Noise and Rough idle

Hi,

I have a 2002 Launch SSV with an Indmar Assault 350 / 5.7 TBI.

Yesterday when we were out with the boat we first spent a few minutes idling in gear. Then we throttled up and got on plane. Almost immediately I thought there was a strange noise and felt a vibration in the boat. We turned off the engine. Then started the engine again and idled in neutral for a while. Once we put the engine in gear the vibration and noise got worse. Hard to explain the noise. But a clunking maybe... We were towed to the dock where the boat is mooring.

Today I went down to do some troubleshooting and the engine starts right up but does run rough and I can hear a ticking/clicking noise from front of engine (towards the transom in the V-drive). I have pulled of the waterpump and belt (which have been squealing quite badly the last few outing, I had just gotten my replacement belt delivered). Noise is there without the waterpump as well.
I tried putting it in gear today and today I couldn't hear any difference with it in gear or out of gear.

I tried revving a bit and while the noise is not as apparent I would say it is most likely just because the engine is making more other (good kind of) sounds.

I started doing a compression test today and found that I had 170-185 on 3 of my 4 cylinders on port side of engine. The last one had 210. I could also see that there were some moisture on the plug. And this seemed to be water not fuel. I didn't continue with the starboard side of the engine as I wasn't sure I wanted to keep cranking the engine. The plugs were all black sooty, even the one that were wet. No rust at least.

Could this all be due to a bad manifold/riser gasket for example. Could that develop so quickly that all of sudden I would hear a strange noise even at 2500 + RPM? Or is this just another issue I found while checking for the root cause of my first problem? Not sure the running rough condition is actually what is causing my noise, but at least it should/could be causing my vibration.

Any input greatly appreciated!

A video with the noise:
https://www.dropbox.com/s/2spti3lkfo..._3617.MOV?dl=0


Thank you,
Mike

I'll be interested to hear what other folks have to say, but I wouldn't get WAY bent out of shape worrying about major engine problems just yet. In a compression test, all cylinders should be within 10% of each other. If say, your average is 180, then 210 is ~15%... a little more than you'd like but I wouldn't think 'here's me smoking gun' and go rip the engine out. Also, wet plugs could be tough to say water vs. fuel. Does the oil look like chocolate milk?

Engine sounds a little rough to me but I can't hear the clicking. Could the noise /vibration have been some cylinders not firing? I think I'd start with the electrical basics and see what's you see. How is your distributor cap & rotor? Are the plugs and wires in good condition? Also make sure both injectors look like they're spraying okay.

Hi,

The oil looks normal, a bit black, bit not milky.


I cranked the engine without any plugs in and no water came out of holes.

Finished the compression test and found one cylinder with zero compression. Pulled valve cover and found a broken exhaust valve spring. I have ordered new springs but what would cause this?

Valve itself looks and feels fine.
I tested and retested the 0 compression cylinder and on one revolution of the engine valve did close so I got 80 psi on one crank.

Mike

Hi, The I had the exact same thing happen to my 1991 SkiNautique. The culprit was most likely moisture build up during winter storage that caused one of the valve springs to corrode and eventually break. It sounded like a loose nut rattling in one of the cylinders. Knowing that you are a Swede, Froggy.se sells some additive that prevents this from happening.
/Rikard