1990 70hp VRO Johnson (constant overheating)

[Darren]

Once I plane out it is only a matter of minutes before the alarm goes off. The water coming out from the exhaust is boiling hot, but the water out of the peehole is cold or lake temperature. Had a new impellar put in and have a constant steady flow. Is this telling me that it is most likely a thermostat that is not working or some kind of blockage in the block??

[boats.net]

Yes, I agree, sounds like the thermostat.

[laderwell]

I would probably suspect a thermostat also

[Rebel Sympathy]

Once I plane out it is only a matter of minutes before the alarm goes off. The water coming out from the exhaust is boiling hot, but the water out of the peehole is cold or lake temperature. Had a new impellar put in and have a constant steady flow. Is this telling me that it is most likely a thermostat that is not working or some kind of blockage in the block??

Could also be a bad temperature switch. in the cylinder head (brown wire).
I'd sure change the thermostats first......

[cosmo1957]

Could be an air lock .... there is some info on relocating the tell tale to top of engine to correct this.
CDI Electronics Practical Outboard Ignition Troubleshooting
got to page 117 on this link

Shawn