Thread: F100 Yami - A guy's gotta know...

If'n you're following along, I bought a broke 100 HP Yamaha cheap. It's a 2000, and supposably the engine is seized. Well, it turns. 1st good news.

So now I wanna do a compression test but the starter motor is shot. A hand cranking compression test shows some compression. YAY, cause if its holding some, then the valves should be OK. 2nd good news.

But now a guy just has to know. What's the compression! A new starter motor has been ordered, but it won't arrive till next week, and I wanna know.

Well, that starter motor just has to come apart now! It turns and engages the flywheel, but no makey going around. The starter clutch ain't clutching. It's fried. Hmmm......now what?

I take her apart, and sure enuf, clutch spins both ways, it's supposed to only go one ways, not both, not good. I jammed a buncha thin slivers of sheet metal into it's bearing, and shoved most of it all backl together, and I can get it to spin and turn the motor, yay 3rd good news.



And now I can do the compression test. Hmm, I was too lazy to reinstall the solenoid, so I improvised....



A pair of backwards pliers hold the pinion in place just fine.

And before the jammed sheet metal gave up the ghost I was able to get compression off the cylinders. Only got one chance and really not a clean run at them but they all compressed anywhere from 120 to 160. I tried to do the 120 again but No Bueno, starter motor clutch made slipping again. So the 4th good new was we have compression, yay!

Originally Posted by Rojo

It's old enough to leak in the water passage area anyway. We have a 250 in the shop right now, a 2008, the one I posted recently. It was ate up with rust on the inside in the oil pan area. I assume from the water leaking out of the exhaust but not in the oil. Finally made it to the oil pan. All toast. My guy ended up buying a used 2012 250 from someone who upgraded to a 300hp.

FYI, the previous owner showed me his receipt for a head and block replacement on this motor four months before he says it seized on him. So it should be, if not new, newly inspected stuff, and hopefully not rusted. dono for sure, but time sill tell whilst I tear her down. Won't get to tear it down any further till late next week though, life interrupts my projects yet again. doh


PS. The oil pump was replaced at the same time the head and block was. And, when I drained the oil I found no water. still, time will tell