How do I check for a cracked block or head?

[regulator23]

My 20HP 4 stroke got hot and while I was trying to get water to cool it (through ears, in a bucket), I think I might have messed up because now it will only run at idle. When I try and speed it up, it dies. Is there an easy way to tell if it's a major issue like a cracked block or something?

[ausnoelm]

Best explain exactly what you mean by things like "trying to get water to cool it" "ears in a bucket" why did it over heat in the first place?

[99yam40]

There is nothing that should shut off a motor except running out of fuel or spark going away (like turning off the key or operating the kill switch)

check plugs for signs of water getting into the cylinders if you are looking for cracked block/head type of stuff

[regulator23]

Check for cracked block

Hi, Thanks for responding. I was running it (for the first time after I bought it) and the overheat light came on and it reduced to idle. I idled back to shore and pulled it out of the water. Hooked it to ears and it still got hot and went to idle. I put it in a bucket and same thing. I pulled the thermostat and checked it and it was opening properly. The last thing I did was connected the hose to the flush port and turned the water on before I started it (thought this might have have done damage since it wasn't running when I turned the water on). Anyway, same thing occurred. Then I pulled the impellor and saw it was shot. I replaced it and the water flows strong now, but it will not get up passed idle speed.

I really have no idea what might be wrong and thought that I might have cracked the block or something. It starts right up and runs good at idle but stalls immediately when you try to give it even a little gas.

[99yam40]

not enough fuel will cause a shut down when raising RPM

maybe just a carb cleaning is needed, hard to tell from where I am sitting right now

[TownsendsFJR1300]

Obviously the PO didn't take care of it and didn't bother mentioning the overheating issue (which would have been well known). IE, the motor was not serviced properly over the years.

To confirm, the engine is NOT overheating now, correct? Were you able to recover most/all of the impeller parts?

Did the engine, (since in your possession), EVER accelerate properly and pick up RPM's?

If not, agreed on cleaning the carb(s). Their likely all varnished up.

Make sure you pull ALL the JETS and make sure yo can see light thru them. There's some VERY SMALL orifices that will clog easily, especially with ethanol fuel and if it sat for over a month (without stabilizer).

If you don't see light thru ALL the jets, the carb is NOT clean.