Mercury 850 no water coming from tell tale.

[Jdevon_14]

Hey guys I just bought a merc 850 thunderbolt and the guy said it had a weak water pump. I took it apart and the impeller looks really good. The fins were bent back from rotation but no cracks or anything. The tell tale was plugged but I cleared it and can blow air through the hose. I hooked it up to muffs today and ran it for about 10 mins. Used a temp gun on it and it wasn't over 115. The only place warm water is running out of it is the prop. Just curious if that is normal and what could be causing the water to not come out the pisser. Also put my finger over the hose for the pisser and could feel suction for the first couple seconds after starting.

 

[Chris1956]

First of all, since you do not know how old the inpeller is, change it, the wearplate and the two gaskets. If the gearoil is not new and clear, change it and the waterpump base seals.

Water should exit the telltale within a few seconds of starting the motor. That motor should run dead cold at idle on a flusher, as it has no thermostat. If you run it under load, I expect you will overheat almost immediately, and likely ruin the motor.

 

[Jdevon_14]

I planned on doing all that just waiting for the parts to come in. Was just seeing if the water running through the prop was normal or if something else was going on besides the waterpunp being weak. Mechanically inclined just new to outboards.

 

[Chris1956]

Some water will always go thru prop to cool exhaust. At idle on flusher this will be lukewarm.

Most cooling water comes out grating above antiventilation plate. This will be garden hose water temperature (cold) at idle on flusher. Telltale will also be same temp as garden hose.

When running motor in water, telltale should always be cool to warm. Motor will run warmer depending on load. Cooling system is designed to just keep motor cool enough. If you have high load, motor will run a bit hotter. It is therefore important to keep carbs clean and waterpump in good shape, and run correct prop.