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Strange vibrations!


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Hello everyone! I need some help with some strange vibrations that I'm getting on my 03' Sunsetter Lxi. I don't know if you will need to know this, but it has the LS1 engine and stainless prop and all underwater gear. I was on Union lake in Michigan today, and drove slowly through a pretty shallow area in the water (depth gauge read 3.7) I think my draft with a boat full of people is about 3.1 (only had 2 on it though including me today). After this I stopped the engine, and anchored for a bit. Then when I started it back up and put it in drive, I noticed a decent amount of vibration. I dove into the water to check the prop for any nicks and or seaweed. I found nothing and went under several times to make sure. I found this to be the case at low RPM, but also had (less) vibration in neutral at that same RPM band.

Then after I realized that it couldn't possibly be a problem with the prop, I began to think it was a problem with the engine. I checked the oil, and trans fluid and everything seems to be fine. Then when I pulled it out of the water shortly after, I confirmed that there were no problems with the prop.

I'm clueless! The boat has 40 hours on it, and has fresh oil. When I bought the boat a few weeks ago, I put gas in it and am not sure how long the gas that was already in there was sitting. The previous owner said that he put a stabilizer in the tank before he stored it. I'm getting down to about a 1/8th of a tank on the same tank of gas. Could it possibly be just bad gas?

Being a first time boat/Malibu owner, I think I'm going to take it to Skier's Pier (local dealership) tomorrow to see what's up. I just don't want to damage anything! :(

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It could be numerous things like a bad tank of gas, bent prop, shaft out of alignment, motor mounts loose, etc. Is the vibration only when it's in drive? If so the shaft needs to be realigned; if it's vibrating even in neutral then you know it's not the prop or the shaft. Start with that and let us know!!! Good luck.

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It could be numerous things like a bad tank of gas, bent prop, shaft out of alignment, motor mounts loose, etc. Is the vibration only when it's in drive? If so the shaft needs to be realigned; if it's vibrating even in neutral then you know it's not the prop or the shaft. Start with that and let us know!!! Good luck.

It does vibrate, but not nearly as much when it is in neutral.

Ok, so I think I may try the gas idea. Is there any way to drain the gas that is in there now? I just want to get a full fresh tank.

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It could be numerous things like a bad tank of gas, bent prop, shaft out of alignment, motor mounts loose, etc. Is the vibration only when it's in drive? If so the shaft needs to be realigned; if it's vibrating even in neutral then you know it's not the prop or the shaft. Start with that and let us know!!! Good luck.

It does vibrate, but not nearly as much when it is in neutral.

Ok, so I think I may try the gas idea. Is there any way to drain the gas that is in there now? I just want to get a full fresh tank.

I'm being a jerk here I know, but the easiest way to drain gas from a boat like this is to start the engine, load the boat down with friends and go play on the water -- a lot.

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I'm being a jerk here I know, but the easiest way to drain gas from a boat like this is to start the engine, load the boat down with friends and go play on the water -- a lot.

Ok, yes that would ideal. I just worry about damaging something if it's not the gas that is causing the problem.

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Check the spark plugs for a fouled plug. Make sure the plug wires are in the proper order. Check for cracks on the dist cap and rotor/clean contacts. If thats all good then it could be an injector.

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Check the spark plugs for a fouled plug. Make sure the plug wires are in the proper order. Check for cracks on the dist cap and rotor/clean contacts. If thats all good then it could be an injector.

Thank you! I checked all of that, and everything is good! The engine is so clean, I think I might have dinner off of it. :-)

Actually, I put it in the water to try to get the rest of the gas out of the tank, and I got it down to where it reads almost empty. Then on the way home I stopped at the dealership to have them take a look at it. They gave it a once over and also said it looks like everything is fine. They said that the rattle I'm hearing could be a loose resonator plate. They want me to leave it there so they can do a lake test. I didn't leave it just yet since I didn't have my cover with me and they leave it outside. They also said that they have about 6 boats in front of me. :-( I think I'm gonna fill it up with fresh gas tomorrow and see what happens. If it still does the same, then I will let the dealership have it for a few days.

Also, when I went out to get the trailer to take it out of the water, there was a two foot long scratch in the trailer! GRR!!! This boat is driving me nuts! You know what they say about what boat stands for. Break Out Another Thousand. :-(

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A 2003 with 40 hrs on it??? Wow. Good chance that at some point there has been some old fuel that has gummed up something. New fuel and perhaps some additive to clean the system and give it a good run.

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Check the spark plugs for a fouled plug. Make sure the plug wires are in the proper order. Check for cracks on the dist cap and rotor/clean contacts. If thats all good then it could be an injector.

Thank you! I checked all of that, and everything is good! The engine is so clean, I think I might have dinner off of it. :-)

Actually, I put it in the water to try to get the rest of the gas out of the tank, and I got it down to where it reads almost empty. Then on the way home I stopped at the dealership to have them take a look at it. They gave it a once over and also said it looks like everything is fine. They said that the rattle I'm hearing could be a loose resonator plate. They want me to leave it there so they can do a lake test. I didn't leave it just yet since I didn't have my cover with me and they leave it outside. They also said that they have about 6 boats in front of me. :-( I think I'm gonna fill it up with fresh gas tomorrow and see what happens. If it still does the same, then I will let the dealership have it for a few days.

Also, when I went out to get the trailer to take it out of the water, there was a two foot long scratch in the trailer! GRR!!! This boat is driving me nuts! You know what they say about what boat stands for. Break Out Another Thousand. :-(

Dude, you still got a half to 3 quarters tank left in there. ROFL.gif

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Don't trust the fuel gage without visual verification. I'm guessing your gas tank is hidden under the truck like mine which makes the visual tough. Try to get all that old crap out of there. When I changed my fuel filter last month I saw a third of a tank and my gas guage says empty. Can you make an appointment with the dealer for one day service instead of leaving the boat with him till 'he can get to it'?

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Don't trust the fuel gage without visual verification. I'm guessing your gas tank is hidden under the truck like mine which makes the visual tough. Try to get all that old crap out of there. When I changed my fuel filter last month I saw a third of a tank and my gas guage says empty. Can you make an appointment with the dealer for one day service instead of leaving the boat with him till 'he can get to it'?

Seriously? Wow! This boat gets a lot better gas hourage than I thought! That really may be the problem, the only time I filled it up it read a half tank, and being that it was a 35 gallon tank I was shocked to see fuel pouring out of that thing when I had only put like 10 gallons in. You say that you can "visually verify" the amount of fuel in the tank. Does this mean that it is made of a clear plastic? I guess we'll HAVE to do some skiing or something, or maybe I'll ride around all day with the wedge down. That's sure to empty the tank!

Yeah I could probably schedule an appointment with them, good thinkin!

Thanks for all your help my Malibu peeps!

Edited by LS1boarder
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No, you can only see the tank if you take the trunk apart, which I had to do to change the fuel filter. I have since relocated the filter to under the removeable floor board. Knowing your fuel gauge come with a few fill-up experiences.

For instance, I ride around on empty for two hours, then my fill up is about 35 gal. in a 41 gal. tank.

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An 2003 boat with 40hrs on it!!!!!!!!!! Previous guy never used it and it probabbly sat a bunch with gas in it. I would either drain it of just fill it if its only got 1/8 of a tank. If it keeps doing it through another full tank, I would think it needs to be tunned up, because the plugs are gummed or injectors. But go though another tank first. I run my boat all year but I know people who still treart the fuel and gunk there engine, especially carborated ones, after a year of sitting.

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An 2003 boat with 40hrs on it!!!!!!!!!! Previous guy never used it and it probabbly sat a bunch with gas in it. I would either drain it of just fill it if its only got 1/8 of a tank. If it keeps doing it through another full tank, I would think it needs to be tunned up, because the plugs are gummed or injectors. But go though another tank first. I run my boat all year but I know people who still treart the fuel and gunk there engine, especially carborated ones, after a year of sitting.

Yeah, and you'll think it's even crazier when I tell you that I put about 15 hours on it last year before I bought it from him (it's my mom's fiance), and have put 10 hours on it since I bought it from him. He's really only put 15 hours on it himself. Hmmm, that means he paid about $1133 for each hour he used it. CRAZY!! Crazy.gif

Ok, so back to the issue at hand. I siphoned the gas out of it, and filled it back up with some new premium fuel with some Techron fuel system cleaner. It seems to have made no difference. Actually, it seemed better at first, but then went back the the same level of vibration. Also, it doesn't seem to go as fast. I'm going to try to change my appointment at the dealership to Thursday, I'm off work. Do you think they'll let me go on the lake with them? I want to be very specific about the problem so I can get to the bottom of it.

Maybe some new plugs is the solution. Should I change the plugs, or just let the dealership look at it? Also, I think the vibration I get in neutral is normal engine vibration. When I put it in drive, the whole boat shakes at a low RPM and starts to rattle from the engine compartment. Then it goes away with a bit more throttle, then returns at almost full throttle. (Much softer though)

Thanks for everyone's input!!

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  • 2 weeks later...
Check the spark plugs for a fouled plug. Make sure the plug wires are in the proper order. Check for cracks on the dist cap and rotor/clean contacts. If thats all good then it could be an injector.

You are the winner! The dealership called me today to say that it was indeed a fouled plug. I checked the wires and the dist cap, but didn't actually pull the plugs. They said that it wasn't running on all cylinders. They replaced all the plugs and ran it again, and all was good. I guess I wouldn't have known how to look for a fouled plug. Thanks for all your help! You guys are the coolest!! Thumbup.gif

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I guess I wouldn't have known how to look for a fouled plug.

You take it out and if the bottom looks yucky, it's fouled. Congrats on the fix--now get out on the water! :)

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