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1990 Ski Nautique Dying |
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Trickinainteasy 
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Joined: September-09-2020 Location: Kansas Status: Offline Points: 3 |
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 Topic: 1990 Ski Nautique DyingPosted: September-14-2020 at 4:46pm |
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Hello,
I am posting to see anyone could help me troubleshoot what is causing my friend's 1990 Ski Nautique to decrease rpm, sputter, and die at high rpm. This problem has been persisting on and off for the past two years. He has done the following with temporary alleviation of the problem but it has popped back up. End of 2019 -Rebuilt Carb -Drained Fuel Tank & Cleaned -Cleaned Fuel Pickup in Tank -Replaced Fuel Filter -Cleaned Points -Replaced Spark Plugs For the better part of this summer it has ran well, but in the last month or so at high rpm it will run fine for a few minutes and then lose rpm, and sound like it is back firing. If we do not pull back on the throttle it will die. I am attaching a video of the boat being ran at WOT then dying. We cannot figure out if it is fuel or spark related. If we should start with new cap, rotor, and spark plug wires? Any advice would be much appreciated. Thanks, Nate
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8122pbrainard
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Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Posted: September-14-2020 at 5:10pm |
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Nate,
To me it sounds like the engine is running out of fuel. You stated he cleaned the fuel pick up tube in the tank but did he look at the anti siphon valve at the top of the pick up tube. It looks like a barbed hose fifiing but inside is a ball check. They can get clogged. |
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SNobsessed
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Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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Posted: September-14-2020 at 7:44pm |
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Also try leaving the filler cap a little loose. It may be drawing a vacuum if the vent hose is partially clogged.
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin |
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Baileys140
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Joined: June-11-2020 Location: Palestine, TX Status: Offline Points: 15 |
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Posted: September-15-2020 at 3:42pm |
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Have yall checked the distributor? I bought a 95 sn 351w pcm and it would run great, get up to 45mph then die suddenly and randomly. I replaced the distributor and it seems to clear up the problem
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uncle-buck
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Joined: June-14-2004 Location: United States Status: Offline Points: 327 |
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Posted: September-16-2020 at 8:29am |
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Nate,
Will the engine restart immediately - or does it have to cool off for a period of time before it can be restarted?
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GottaSki
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Joined: April-21-2005 Location: NE CT Status: Offline Points: 3363 |
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Posted: September-16-2020 at 8:55am |
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Definitely running out of fuel and lean surge with pops
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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Trickinainteasy
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Posted: September-16-2020 at 5:29pm |
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Thank you for the ideas guys.
Baileys140 - We have not checked the distributor, is there anything we can look at that might tell us it is bad? uncle-buck - After it dies the engine will immediately start up again. I'm guessing this is probably a good thing. SNobsessed - We took the boat out for some trick sets this morning and on our way back to the dock gave it WOT with the filler cap loose. Still same result after about 10-15 seconds of running. I am leaning towards the probability it is running out of fuel and going lean as well. But, after hearing that might be the case I am concerned we may have been causing damage by leaning the motor out at such high rpm, multiple times(it has been a lingering problem for the past two years). Is my concern warranted or do you think the motor is okay? We are going to try and get to the anti siphon valve and clean it this weekend. I will report back our findings! -Nate
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uncle-buck
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Posted: September-16-2020 at 5:53pm |
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Well, one thing you can do is to run the engine from a portable fuel tank using new fuel hose while also bypassing the fuel filter. In other words, run the new fuel line straight from the portable fuel tank to the fuel pump.
If it runs fine that way, then run it from the portable fuel tank through the fuel filter and to the fuel pump. If it runs fine, that way, the issue is likely the anti-siphon valve or the fuel tank pickup. You wrote in your original post that you cleaned the tank and fuel pickup tube. Did you remove them from the boat? (I think you have to remove the tank in order to remove the tube.) |
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GottaSki
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Posted: September-16-2020 at 6:21pm |
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In my experience witnessing many live with that way too long, is that no harm was done to your engine
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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GottaSki
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Posted: September-16-2020 at 6:23pm |
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What exactly was done to the pickup tube? Was it disassembled, or just inspected?
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"There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing."
River Rat to Mole |
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Baileys140
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Posted: September-16-2020 at 6:24pm |
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SNobsessed
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Posted: September-16-2020 at 9:50pm |
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I doubt it but have not had this problem myself. Sounds iike a vacuum leak but that doesn't make sense for hi speed failure. Keep testing to narrow down the possibilities. Fuel pump, carb inlet filter screen, collapsing fuel hoses - you need test plan to eliminate them all.
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin |
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Gary S
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Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Posted: September-16-2020 at 9:57pm |
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Start with the anti siphon valve- a common well known failure point that has these symptoms.
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uncle-buck
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Posted: September-17-2020 at 1:36am |
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If you think it's the anti-siphon valve, you can temporarily replace it with a regular hose barb. If the issue goes away, install a new anti-siphon valve. You can purchase a new one from Amazon for about $23. It's probably a 3/8 X 3/8 NPT.
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8122pbrainard
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Posted: September-17-2020 at 4:51am |
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TRBenj
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Posted: September-17-2020 at 7:38am |
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Every anti siphon I’ve seen cause an issue was pretty easy to spot once disassembled. Agreed that should be the first place to look based on the symptoms.
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SNobsessed wrote: