Yamaha F100 seized

[tavacska]

The crank was seized and was believed to be the lower unit drive shaft and oil pump. It was running good in the fishing trip one day. When it was time to travel back, it got seized there.

I have lifted the powerhead. I have tried to crank with a wrench but failed to rotate it.
The oil pump and drive shift was in bad form too. The oil pump lower seal has corroded out and drive shaft stuck with oil pump shaft. The inner gear and outer gear of the oil pump stuck too and that's why the lower unit stuck there and can't be rotated.

However, to my surprise, the power unit crank still can't move. How hard shall I try to rotate it using a wrench? It was hanged in the air and hard to apply force though. I have tried my best but it doesn't move.

I will try to put it back to the lower and try again.

 

[saltchuckmatt]

The crank was seized and was believed to be the lower unit drive shaft and oil pump. It was running good in the fishing trip one day. When it was time to travel back, it got seized there.

I have lifted the powerhead. I have tried to crank with a wrench but failed to rotate it.
The oil pump and drive shift was in bad form too. The oil pump lower seal has corroded out and drive shaft stuck with oil pump shaft. The inner gear and outer gear of the oil pump stuck too and that's why the lower unit stuck there and can't be rotated.

However, to my surprise, the power unit crank still can't move. How hard shall I try to rotate it using a wrench? It was hanged in the air and hard to apply force though. I have tried my best but it doesn't move.

I will try to put it back to the lower and try again.

Huh? What are you asking?

 

[tavacska]

I was going to ask what next steps should I take to look for causes.

Here are some updates I did today.

I opened the crankcase cover, the crankshaft is full of rust. The crankshaft is stuck because of rust.

My questions are:
1. How bad is it? Is it re-useable or shall I look for new powerhead, new pistons, new crankshaft?

2. What has caused these? What next steps should I take to investigate more? Shall I take apart all the power unit?

3. The cylinder crank case stuck too. Both the shafts got stuck too. It seems all these got seized because of rust. Are these recoverable or should I just drop it to trash and look for new powerhead?

Thanks.

 

[tavacska]

And also here are some picture from bottom of the powerhead. the exhaust is clean, the water passage has some corrosion which is still tolerable to me. I don't know if there could be a hole somewhere in the cylinders. Just FYI for the questions above. thanks.

 

[robert graham]

We’re you running in salt water? …..

 

[racerone]

This gentleman likely picked it up cheap in the hopes of getting it running.--- With a little cash input and input from this site.

 

[99yam40]

I would have to say water was inside the motor.
how come the poster did not mention draining water and oil out?

 

[tavacska]

This gentleman likely picked it up cheap in the hopes of getting it running.--- With a little cash input and input from this site.

Indeed that's my plan. Get some potential with low cost and rebuild it to be a perfect one. That is one of my hobby now.

Racerone, I appreciate your help very much for my mercury top of tower rebuilding. I spent $2000 to rebuild the 40s to top notch and I feel happy about it.

This is my another project and I need specialist's help too.

 

[tavacska]

We’re you running in salt water? …..

I would have to say water was inside the motor.
how come the poster did not mention draining water and oil out?

Yes, it's running in salt water. The motor is now completely dry and the oil in the oil pan is not milky.

I opened the head cylinder and found out the valves all stuck. Not by rust, by very sticky oil gunk . All the bearing holes are blocked by these gunk and can not have lubricant oil go through.

The water passage around the cylinders are fine to my surprise, a little corrosion except one point at the lower corner. That exhaust wall almost not yet is eaten up by corrosion. All the other mating surface is intact. That's the weakest point. And the other areas are just fine even better than any used-one listed in ebay.

Please see pictures.

My question is how do I patch that weakness. Shall I look for a welder or workshop to patch it?

Thanks.