25hp Yamaha getting hot/No water flow. Need Help!

[HalfFast]

I need some help/advice about a 25hp Yamaha. This past Saturday as I was running back to the ramp at WOT my motor started losing rpm’s all the way to the point it stopped. When I tried to restart it, it wouldn’t turn over – locked up. It wouldn’t turn by electric start or by pull rope. Earlier I had noticed there was no water coming out of the “tattle tale”, I figured it was just plugged up and I didn’t have anything to unplug it with and figured it was getting water just not coming out the “tattle tale”. I *****ed to the truck, loaded up and checked to see if the motor would turn after it had cooled off, it wouldn’t. After getting home about an hour later I pulled the cowling off and was able to turn the fly wheel by hand then it would pull and turn over by the rope and starter. I figured I would just unplug the discharge line and it would be fine – WRONG. I disconnected all of the discharge tubing, it was clear. With it disconnected I hooked up muffs to a water hose and started the motor, it would not put out any water. I pulled the thermostat out and tried it, still no water. Figured my water pump must be fried so it pulled it down. Water pump impeller looked fine, not much if any visible wear, no nicks and seemed to have good memory. The bowl and bottom plate looked good and no blockage or debris found. I could blow air thru the discharge hose and feel it come out the pipe going from the pump to the head of the motor so no blockage there. I reinstalled the lower unit and tried it all again with the same results, no water flow with the thermostat in or out, motor in gear or out, idling or at elevated rpm’s. Has anyone ever seen this and what should I do to fix it? Could it be the water pump even though it looks ok? Any help would be greatly appreciated.
Thanks,
HalfFast!

[TownsendsFJR1300]

What year, 2 or 4 stroke, model # is the engine?

There is often a steel pipe that connects the lower unit to the powerhead with O-rings. They do rot away on occassion, o-rings fail/leak and don't allow water to make it to the powerhead even thou the WP works.

If you could post the above information and also go to the upper right, in RED, parts fisch, you'll likely find it..

IE, part #1; http://www.boats.net/parts/search/Ya...202/parts.html

[99yam40]

If it is a old motor then corrosion may have eaten a hole or plugged up some passages.

Drop the lower again and rig up a hose to water tube and turn on water to see if it comes out like it should without even starting the motor.
If it does then you know it has to be the pump not pumping properly

[rodbolt17]

and go ahead and pull the cyl head and have it surfaced.
its warped.
once you get water flowing again your next post will be about water in the cyl.

[99yam40]

Not to mention the likely damage to pistons and cylinder walls from it seizing up.
While the head is off have a look to see what the cylinder walls look like

[ausnoelm]

you might be lucky and the motor will be OK, I have seen lots that seized from lack of water, start and run OK for years, as distinct from one that's seized from lack of oil, these usually don't end up so good. OH, and as mentioned, do the head......

[rodbolt17]

I have a C25 head on the bench now that is mostly junk ,needs at least .018 taken off.
same issue,pump failed.
if the head paint changed colors do yourself a favor and go ahead and pull it.
this customer kept fighting it and it leaked water into the engine and now the lower bearing is noisy.
there is NO automatic shut off,what happened is the pistons kept expanding due to heat until they physically stuck in the piston bore.
the head tends to bow in the middle with that kind of heat and then the gasket starts leaking.

[mark mcconnell]

1/2fast, Same problem (almost) w/ 25, 2-cycle Yamaha

Broke down my '05 for periodic maint--reassembled and same thing. No water flow ! Did not smoke it. Redid, used old parts,changed thermostat. Still NO water ! How did your's come out ? Tell me the trick. Dock on Estero island is yours anytime.