knocking noise

[CV16]

Had my boat out Saturday by myself. Everything was great last week. This week it has what sounds like a rod knock at around 3,000 rpm. It's not in the motor though, out of gear it sounds great. I haven't had a chance to look at it yet. Just trying to come up with ideas to check out. I had the drive off and the u-joints seemed good 2 weeks ago. I did take the prop off to grease it up. I'm thinking either motor coupler/gimbal bearing or the u-joints. Is there anything else I could be missing?

 

[SeaDooSam]

It happens on my boat too except not bad enough to fix it yet. My mechanic says it is the u-joints

 

[wkb2460]

Does it sound worse while turning? If it is the u-joints, I wouldn't wait till they get worse.
You don't want one of them breaking while your out on the water.

 

[CV16]

I already have the lower taken off. I have clips on the u-joints so they should be replaceable. I was told some can't be. Now I just have to find the part numbers.

 

[Captaincrisp]

My death noise turned out to be the rubber around my exaust flapers wore out and made a pretty ugly noise more noticable on the hose/muffs then in the water. Just a shot in the dark. But i would make sure its not those guys because they sure had me scared. Hope its somthing cheap and easy

 

[CV16]

Thanks for the heads up. I will look at those tonight.

 

[CV16]

Well, my u-joints sure seem good to me. Gimbal bearing seems fine and alignment is spot on. Where are these exhaust flappers located?

 

[Scott Danforth]

In the y pipe. Remove the rubber exhaust hoses

 

[CV16]

Ok, while I'm at it, I read somewhere that there is a gasket that should be replaced after an over heat. Any clue as to where that's at? I want this to be ready for my trip to Arkansas in a few weeks. I did over heat, so I should at least check on it.

 

[bruceb58]

And if you see that they are melted, just remove them...you don't need them.
https://dl.dropboxusercontent.com/u/83197541/iboats/Exhaust pipe seal obsolete.pdf

 

[CV16]

How in the world do I get these hoses off? Can I get them off without taking other stuff off?

 

[CV16]

Ok, got the one side off. I don't see any type of flap. Does a 2000 5.0GL have them?

 

[bruceb58]

It may not. Can't remember what year they started not putting them on. They don't show up in parts diagrams anymore that's for sure.

 

[CV16]

Got the water in the oil solved. It was the riser gaskets. Still have the knocking sound. Today I'll change the u joints and see if that cures that problem. Sure would love to use the boat at least one time with the family this summer!

 

[Thalasso]

Volvo quit using the flapper in 1999.​

http://www.4shared.com/file/51149475...?cau2=403tNull

 

[Assassin3F]

Might want to go out with some one and sit near the engine while reving past 3000 RPM to try and see if the sound is in the engine or in the drive (i.e. in the water) what your describing sounds a little like valve lash in the head.

I am remembering an issue I had with an old Chevy impala where one of the valve springs started wearing out a bit and at high rpm the valve stopped springing back all the way...that in turn caused the push rod to lose contact with the lifter until it was driven back into position at which point the rod knocked into the valve and slammed it open. My Neighbor diagnosed it for me and fixed it by adjusting the lash. I seem to remember it sounded like a bent rod but not quite as bad a clunk.

 

[CV16]

I'm bringing it to a Volvo Penta dealer today. It's time for somebody else to figure this one out. Working 12 hours a day doesn't leave me any time to deal with it.

 

[CV16]

Holy sticker shock! I can buy a 5.7 long block for the estimate I got today. Turns out I didn't solve the water in the oil, took it out the other day and didn't even leave the dock. I had a faint alarm, hardly loud enough to hear, well, I am a bit hard of hearing too. I pulled the dipstick and it was milk again. I'll be tearing it down.

 

[Assassin3F]

CV16 I have been trying to read up on your water in the oil issue a bit but can't find the original post. I did notice you have a Volvo Penta SX though (caught my eye cause I have the same). I found a thread out here that said the grease nipple for the gimbal bearing will occasionally cause a water leak. It is a slip in nipple from the factory. Is it possible that the water is finding its way into the engine through the crank? (I honestly don't know if that is possible since I never had a gimbal go on me; it is a question as much as a suggestion) If so you might be able to fix it using the solution out here...assuming and hoping that you don't have irreparable engine damage. The other one that comes up most frequently is the bad exhaust elbow.

 

[CV16]

Thanks for the thought. I pulled the plugs and had a lot of water in 4&6. This time I had 0 compression in those two. The gasket was shot for sure. The block looks good. Took the heads in to be magna fluxed, should get them back Wed.