Knocking noise in 15hp yamaha 2003 2 stroke outboard...?

[Zante]

I have this neat 15hp outboard. It's a 2003 Yamaha 15MSHB that makes a knocking noise. IT doesn't make it when the spark plugs are not in. It runs well but I don't wanna run it cause it may break. The block has a crack in it from years ago. But it was welded professionally. I have taken the entire engine apart and the crankshaft and connecting rods are in near new condition. It's not the lower unit. The piston sleeves are new and it has new rings. It's a cool outboard. Connecting rods are good and bearings seem to be okay. I cant find any reason why this noise is here. Please help! Here are some photos!
IMAGES..


http://imgur.com/a/Qkfjl

 

[tommarvin]

Did the knocking noise start after you rebuilt the motor? I would check the crack in the block, there's a special powder shops put on blocks to check for crack.

I would take the whole motor apart, and get the service /rebuild manual,read the whole rebuild section, think it through, and put it back together again.

Torque all bolts and nuts correctly. Are the pistons standard? No knock with plugs out, correct wrist pins? correct bearings ? Reused con rods and pistons, correct rings for your used pistons?

 

[Zante]

It's gotta be correct. I don't have a service manual but will be getting one. I did take motor apart. All bolts seem to be tight. Everything seems tight. I got it for 120$ from the previous owner who said he could never fix the knocking noise. He dove in and tried fixing everything he saw but there was nothing. It's spooky. And the parts are Yamaha certified. Wrist pins are correct, I think original. Everything is original except the sleeves and the bearings

 

[Zante]

actually when I went inside the crank shaft, the engine inside, there was very very little oil. It was actually pretty dry inside. Might this be the problem? Should I oil it up using 2 stroke oil? or four stroke?

 

[Zante]

Sorry to triple post but, the little needle on part number nine in this photo is badly bent. Think that could be the cause...? it's a bearing and the needle holds it in place I guess.....

http://i.imgur.com/UDQN1t0.jpg

 

[tommarvin]

I'm new, I think that's a main crankshaft bearing, that has spun out of its holding hole in the block,if so you better have a machine shop check the crankshaft ,and get new main bearings .

Make sure you use a 20-200 inch pound torque wrench HF has them for 12 bucks.

 

[flyingscott]

If the locating hole is torn out it spun out at some point in time. If not somebody put it together wrong and crushed the bearing make sure both sides of the block are good.

 

[Zante]

Just figured it out guys. The crank was loose. I guess the front engine block where the carb connects, it was worn and when there was compression, it would push the crank toward the block and it would hit the block inside. A solution for this is to clamp it down with a strong rubber piece or to sell it.(rubber piece to tighten the grip on the crank shaft) Sold it for 250... Bad price I know but honestly i'll just pick up another one for cheap. It does need a new housing. the block wouldn't hold in the crank correctly. I am upset but hey I only got it for 130$... I guess i'll stumble upon another deal soon enough.​In other words, the block was not holding the top bearing in correctly. There was a little bit of space, just enough to let the crank hit the side of the block. There is wear an tear on the block there.

 

[tommarvin]

Good for you,the guy(s) before you screwed it up. Get a Yamaha if you can find one.

 

[Zante]

I wanna score one of those Yamaha/mercury mariner motors. I had a 15hp once and it was the best engine I had ever used. By far the best. Maybe ill score another one of those. OR a 4 stroke if I can find a decent one.
​either way the new owner would be willing to put the $$$ into it.