2000 30hp yamaha seized'ish

[jedimaster]

Ok, so I just picked up this motor, and ran it a week ago, it was down a piston, so I checked it out, and one spark plug was dead. no spark, changed the plugs and put it in the water yesterday. Oil was full gas was fresh, let it warm up a bit at the dock, and took off. Hopped up on plane and then it started making a metal on metal sound. so I shut it down and drift to shore. I tied up on the rocks and pulled it and nearly ripped my arm off it was seized. I pulled the cowl and plugs, oil was still up, I could barley turn the flywheel by hand, but I coudl see that all the pistons were moving.
I just pulled the head off and there is an ever so slight score in one of the pistons. Can't even feel it by hand. The top and the bottom cylinder head and piston appear to be damaged. I can turn the engine over by the flywheel with great force. I think whatmay have happened is for whatever reason the oil injection stopped working.
Anyway, not a huge deal to pre mix, but here s the burning question. What do you figure happened internally? Pistons move up and down and none are falling out. Did I just spin a bearing? I would think if it was a broken cran or connecting rod one piston wouldn't be moving at all? I can turn the engine over by hand with alot of force its free in some areas but get very hard near impossible to turn in some spots.

I presume I am gonna have to pull the whole powerhead to fully diagnose the problem, so does anyone have a link to an online shop manual for a yam 30? Or does anyone have a breakdown of what's gotta come out to exposed the crank and rods?

 

[jedimaster]

Re: 2000 30hp yamaha seized'ish

 

[rodbolt]

Re: 2000 30hp yamaha seized'ish

motor is blown.
the chunks are pieces of either piston rings or wristpin bearings.
if the oil pump fails it typically takes out the crank not the piston.
oil pump failure on that engine is rare.
I would also open up the carbs and go through the cooling system, only after crank and rod inspection and boring the cylinders for new pistons,wristpins and pin bearings and retainers.

 

[jedimaster]

Re: 2000 30hp yamaha seized'ish

Whats the easiest way to get into the crank area for inspection? Its not so much chunks as it is dents both on the piston and the Cylinder head. Yah I found it very odd that the oil pump would fail but, what else could have caused this? Didn't find any debris anywhere.

 

[jedimaster]

Re: 2000 30hp yamaha seized'ish

Ok, so I have the carbs, Electrica, oil and fuel systems removed, as well as the flywheel cover.
How can I remove the flywheel without breaking anything without using a flywheel removal tool like in the seloc? It says not to use an impact gun for removing the bolt...

 

[jedimaster]

Re: 2000 30hp yamaha seized'ish

Ok, so I have it now fully dismantled. I have the powerhead off the lower unit, and on the bench, I have one half pulled off. I am looking at it and I don't see anything that would indicate anything that self destructed. or that would be causing the binding. but still if I try and rotate the crank shaft by hand it gets stuck.
The one connecting rod is a slightly different color than the others perhaps this is the piston with the problem? How should I go about figuring out what it is thats broken? If I take the crank out with aeverything attatched I don't see anything obvious either. If I move the bearings on the crank those some of them feel a bit loose/gritty. But I am not too sure how they shoudl feel.

 

[jedimaster]

Re: 2000 30hp yamaha seized'ish

The crank is weird looking. How does it all come apart? I could see any bolts or anything? Is it pressed together?
After further inspection I would say that the bearings are toast on it.
Presuming this is the issue. I can get the pistons cleaned up and re done. But how much would it typically cost to have the bearings replaced on a motor like this?

 

[rodbolt]

Re: 2000 30hp yamaha seized'ish

trust me.
google Akermann marine wilmington NC.
they used to do all my yamaha,tohatsu and suzuki built up crank work.
some motorcycle shops can still doit and the parts are avalible from yamaha.
once the crank and rods are known good/rebuilt.
have all 3 cylinders bored to the next oversize,then new rings,pistons,pins and pin bearings and retainers.
clean the carbs replace the fuel pump replace the water pump and T-stat claen the engine oil tank and lines.
reassemble and break in per service manual.
do routine maint and that motor runs for years.
take some pics of the piston sides and post them.