1999 Yamaha V6 2-stroke outboard seizure?

[Strainstress1979]

I have a 1999 Yamaha 200 V6 2 stroke outboard that i bought with my 20ft Make several years ago. I bought the boat with this rebuilt engine and just had service done on the engine about 1 year ago. The engine has been running like a champ until about a week ago. I was about ? mile from the dock when the motor started struggling to run like it wasn?t getting enough gas so i put it into idle checked the fuel lines and everything looked good. I engaged the throttle and went full out when it started to struggle again so i pull back on the throttle and as i was going into neutral the engine stopped and hasn?t started since. I thought it was an electrical or fuel problem. Checked the electrical situation and everything look good except for the starter so I replace that but the engine still wouldn?t start. I tried turning the flywheel by hand and noticed it make about 300 degrees of rotation and then would stop so i would turn it back in the opposite direction and again, 300 degrees and it would stop. I took out the spark plugs and tried to start the engine thinking I may have vapor lock but no success. It just won?t turn over. I?m thinking i have a stuck piston head in one of the cylinders and I?m going to have to re-bore that cylinder. Before I start I was wanting some thoughts on if my diagnosis is correct or if there could be another problem and how to check for it. Also if anyone has any comments about me trying to repair this myself. I was going to remove the powerhead and have my local machine shop re-machine the cylinder and then get a sleeve to the cylinder. Is this too big a job for a novice?

 

[99yam40]

Re: 1999 Yamaha V6 2-stroke outboard seizure?

it is not a stuck piston, if it was it would not let motor move as far as it does.
Maybe rod turned loose and getting into something or stretched and piston is hitting head. need to open it up to see what is going on.

If you have never worked on outboards yourself ,in my opinion you are in over your head.
But with a Yamaha service manual you might get through it, but I would let someone that knows these motors very well do it and find the cause so it will not happen again

 

[Strainstress1979]

Re: 1999 Yamaha V6 2-stroke outboard seizure?

THank you for the good information. I'm buying a manual today and enlisting the help of my brother who is an auto mechanic as well as a buddy who has work on his own outboard. Between the 3 of us and the manual we make one decent marine mechanic. I'm guessing the only way to really find out what's going on is to take the case of and look inside.

 

[Capt Ken]

Re: 1999 Yamaha V6 2-stroke outboard seizure?

If a rod came loose then look for a hole in the side of the block. Otherwise remove both heads and see which piston isn't moving. Sounds like a piston seized and and the dome has separated from the skirt. Rod moving but piston ain't.