Problem is fixed, but must document... Starboard engine cutting out while wakesurfing

[tdonoughue]

(Submitting this on behalf of @Scottintexas and myself. Scott came down today, brought his toys, and patiently tried to get me up on one of his wakesurf boards. While I was resting, piloting the boat, Scott was taking a turn and then...)

Fatsacs on the swim platform, a big one over the gas tank and a little one up by the helm, sufficient to sink the swim platform by at least a couple of inches. Surfed from 11am, but about 1pm or so, as I was towing him along, suddenly the starboard engine started surging. Actually, on examination of the tachs, the engine was like cutting out. When I got it up to ~7k rpm, without moving the throttles, rpms would drop to like 3k, then shoot back up to 7k, then down to 3k--very cyclical and very steady. If I went at 5k rpm, both engines did fine--no issues. As soon as I would get to 6.5k or 7k rpm, only the starboard engine would start cutting out like that.

As I said, we were able to diagnose and fix the problem on the water, so this is not live. Please do not panic for us. But we thought it would be fun to hear some of your ideas on what it was and share how we cracked this nut... Plus, then it leaves another breadcrumb for the next one who has such an issue.

What do you think was wrong? What would your diagnostic steps be?

 

[buckbuck]

Wait...two guys on a boat surfing on a Thursday.

I don't see anything wrong and my diagnostic report will include a plan to retire and join you guys.

 

[FSH 210 Sport]

(Submitting this on behalf of @Scottintexas and myself. Scott came down today, brought his toys, and patiently tried to get me up on one of his wakesurf boards. While I was resting, piloting the boat, Scott was taking a turn and then...)

Fatsacs on the swim platform, a big one over the gas tank and a little one up by the helm, sufficient to sink the swim platform by at least a couple of inches. Surfed from 11am, but about 1pm or so, as I was towing him along, suddenly the starboard engine started surging. Actually, on examination of the tachs, the engine was like cutting out. When I got it up to ~7k rpm, without moving the throttles, rpms would drop to like 3k, then shoot back up to 7k, then down to 3k--very cyclical and very steady. If I went at 5k rpm, both engines did fine--no issues. As soon as I would get to 6.5k or 7k rpm, only the starboard engine would start cutting out like that.

As I said, we were able to diagnose and fix the problem on the water, so this is not live. Please do not panic for us. But we thought it would be fun to hear some of your ideas on what it was and share how we cracked this nut... Plus, then it leaves another breadcrumb for the next one who has such an issue.

What do you think was wrong? What would your diagnostic steps be?

Fuel starvation.

Move ballast around ?

 

[2kwik4u]

Forgot to turn the bilge pump on?

 

[rad1026]

Check that plugs are in and locked. Check for obstructions in impellers. Check that kill switch is in correctly. Check that clean out hatch is down and locked. Check that bilge is working and no water in engine compartment. Check oil level. Check battery cable tightness. Hmmm, if it isn't one of those things I would probably be drinking a beer and thinking a little deeper.

 

[rad1026]

Oh, check spark plug wires are not loose.

 

[Babin Farms]

Cleanout plug not seated, ballast bag on platform preventing the hatch from popping/blowing up, not noticeable due to having the ballast bag back there and the lower swim deck under water, building pressure and relieving pressure as you tried to go.

 

[buckbuck]

So I am also thinking fuel starved. Is it possible you leaned it over so the fuel in the tank blocked the vent creating a low pressure in the tank?

 

[tdonoughue]

So, lots of good guesses (and many of the things that we were checking). Here is what we found:

Plugs were well-seated. Nothing in the impellers. Newly-done 4200 on the intakes all intact and happy.

Kill switches on the back deck looked fine, but wedged a towel in there to push them down some more. No difference.

Checked the engine compartment: no water. Had to drain the bags in order to get to both the engine compartment and the swim deck. Problem continued nonetheless. Only the starboard side.

Had 3/4+ of a tank of fuel. But were not able to rule out some fuel pump issue (until we actually found the issue--that was not it). Checked the oil: dead at the middle on the starboard engine (about 5/8 between the E and F on the port).

Bilge pumps working fine.

Did not check the battery cables or the spark plug cables. Those are good ideas we should have done.

The solution:
We took it for a run at <6k rpm to see if we could work it out. Was at 3/4 tank, so steered toward the fuel dock and let it run a bit. After a good 5-10 min, tried it again and again when I pushed it higher, it started cutting out the same way. @Scottintexas had the idea to leave the hatch open and he would observe the engine as I piloted and made it do it again. When it did it, I stopped and he reported that the hose from the air filter to the engine on the starboard side was moving--actually collapsing each time the engine cut out. I removed the air filter on that side (which looked fine) and then tried it again. No pulsing and no cutting out.

So then I was looking again at the air filter. And I looked down and figured out that some of the soundproofing I added 6 months ago had come loose from the side RIGHT IN FRONT OF THE AIR INTAKE to the air filter box. As the engine sped up, there was additional suction, which drew the egg crate over the air intake, causing the engine to die. As it died, the suction decreased, the egg crate flapped back and the engine came back to life.

Hopefully, if someone has an issue like this in the future, they will check at the air intake to the air filter box for obstructions.

 

[FSH 210 Sport]

So, lots of good guesses (and many of the things that we were checking). Here is what we found:

Plugs were well-seated. Nothing in the impellers. Newly-done 4200 on the intakes all intact and happy.

Kill switches on the back deck looked fine, but wedged a towel in there to push them down some more. No difference.

Checked the engine compartment: no water. Had to drain the bags in order to get to both the engine compartment and the swim deck. Problem continued nonetheless. Only the starboard side.

Had 3/4+ of a tank of fuel. But were not able to rule out some fuel pump issue (until we actually found the issue--that was not it). Checked the oil: dead at the middle on the starboard engine (about 5/8 between the E and F on the port).

Bilge pumps working fine.

Did not check the battery cables or the spark plug cables. Those are good ideas we should have done.

The solution:
We took it for a run at <6k rpm to see if we could work it out. Was at 3/4 tank, so steered toward the fuel dock and let it run a bit. After a good 5-10 min, tried it again and again when I pushed it higher, it started cutting out the same way. @Scottintexas had the idea to leave the hatch open and he would observe the engine as I piloted and made it do it again. When it did it, I stopped and he reported that the hose from the air filter to the engine on the starboard side was moving--actually collapsing each time the engine cut out. I removed the air filter on that side (which looked fine) and then tried it again. No pulsing and no cutting out.

So then I was looking again at the air filter. And I looked down and figured out that some of the soundproofing I added 6 months ago had come loose from the side RIGHT IN FRONT OF THE AIR INTAKE to the air filter box. As the engine sped up, there was additional suction, which drew the egg crate over the air intake, causing the engine to die. As it died, the suction decreased, the egg crate flapped back and the engine came back to life.

Hopefully, if someone has an issue like this in the future, they will check at the air intake to the air filter box for obstructions.

That was a tough one to solve! Good on you for making a run with the engine hatch open. Glad you were able to find the problem!

 

[zipper]

Late to dinner again...I was going to say that the fat sac was blocking air flow to the engines behind the seatback but that would effect both engines. I knew that was not it when you stated the problem resumed after draining the bags. Kudos to Scott for his idea.

 

[2kwik4u]

So, lots of good guesses (and many of the things that we were checking). Here is what we found:

Plugs were well-seated. Nothing in the impellers. Newly-done 4200 on the intakes all intact and happy.

Kill switches on the back deck looked fine, but wedged a towel in there to push them down some more. No difference.

Checked the engine compartment: no water. Had to drain the bags in order to get to both the engine compartment and the swim deck. Problem continued nonetheless. Only the starboard side.

Had 3/4+ of a tank of fuel. But were not able to rule out some fuel pump issue (until we actually found the issue--that was not it). Checked the oil: dead at the middle on the starboard engine (about 5/8 between the E and F on the port).

Bilge pumps working fine.

Did not check the battery cables or the spark plug cables. Those are good ideas we should have done.

The solution:
We took it for a run at <6k rpm to see if we could work it out. Was at 3/4 tank, so steered toward the fuel dock and let it run a bit. After a good 5-10 min, tried it again and again when I pushed it higher, it started cutting out the same way. @Scottintexas had the idea to leave the hatch open and he would observe the engine as I piloted and made it do it again. When it did it, I stopped and he reported that the hose from the air filter to the engine on the starboard side was moving--actually collapsing each time the engine cut out. I removed the air filter on that side (which looked fine) and then tried it again. No pulsing and no cutting out.

So then I was looking again at the air filter. And I looked down and figured out that some of the soundproofing I added 6 months ago had come loose from the side RIGHT IN FRONT OF THE AIR INTAKE to the air filter box. As the engine sped up, there was additional suction, which drew the egg crate over the air intake, causing the engine to die. As it died, the suction decreased, the egg crate flapped back and the engine came back to life.

Hopefully, if someone has an issue like this in the future, they will check at the air intake to the air filter box for obstructions.

This is hilarious.

Had a Syclone years ago at a national meetup do something similar. Guy put a big turbo on it, and when it got into boost it wouldn't suddenly and rather abruptly drop boost and fall on its face. Come to find out, the turbo was sucking the cobra elbow shut once the engine had heated the elbow to make it a little softer. Took a few hours to diagnose since we couldn't watch the engine while it was doing it.

Good find and excellent troubleshooting!!

 

[Scuba_ref]

Just now getting to this thread...my thoughts: could the sound proofing be loose and starving the engine for air when the suction increases with the rpms? Probably not likely but just a really wild guess!

 

[Ian M]

(Submitting this on behalf of @Scottintexas and myself. Scott came down today, brought his toys, and patiently tried to get me up on one of his wakesurf boards. While I was resting, piloting the boat, Scott was taking a turn and then...)

Fatsacs on the swim platform, a big one over the gas tank and a little one up by the helm, sufficient to sink the swim platform by at least a couple of inches. Surfed from 11am, but about 1pm or so, as I was towing him along, suddenly the starboard engine started surging. Actually, on examination of the tachs, the engine was like cutting out. When I got it up to ~7k rpm, without moving the throttles, rpms would drop to like 3k, then shoot back up to 7k, then down to 3k--very cyclical and very steady. If I went at 5k rpm, both engines did fine--no issues. As soon as I would get to 6.5k or 7k rpm, only the starboard engine would start cutting out like that.

As I said, we were able to diagnose and fix the problem on the water, so this is not live. Please do not panic for us. But we thought it would be fun to hear some of your ideas on what it was and share how we cracked this nut... Plus, then it leaves another breadcrumb for the next one who has such an issue.

What do you think was wrong? What would your diagnostic steps be?

Was it the clean out plugs that came loose ?

 

[Scottintexas]

Was it the clean out plugs that came loose ?

Post #9 - air supply

 

[Scuba_ref]

Loved that band!

 

[buckbuck]

You're kinda old.

 

[Scuba_ref]

You're kinda old.

@buckbuck full on old at this point!

 

[Tgen2013]

Just like a Yamaha. the fix is simple,...and nothing to do with the mechanical manufacture of the motor. I love these boats.

Actually, anyone above 25 is "OLD". Why do I say that, because empirically the insurance companies have deemed this SO,.............LOL.

Besides you should not concern yourself with your chronological age. What matters is you biological age, and what you can DO or not do.

Too many in our country have spent their youth in pursuit of wealth, all while squandering their HEALTH. Then they in vain expend all thier wealth trying to regain their health. For most its too late.

Your body is the greatest device you will ever own. A high functioning person in older years with great health is vastly more "wealthy" (even with modest means), than a monetarily indulgent person in poor health.