Water pump / steam ?

A buddy of mine has a mid 90's Mercury 9.9 that was steaming big time with no water from the tell tale on the way in from duck hunting today. He also said he saw it spitting water from the tell tail in pulses prior to the steam pouring out and the pulses of water totally stopping. We killed the motor & used the electric to get back to the ramp to avoid overheating it.
What would be the first thing you would look at? Water pump? Clogged water jacket? I'm no mechanic but figured it has to be getting water to make the steam.
Thanks!

Impeller, water pump. When was the last time the impeller was changed?

If it was July or August I would check for weeds first. Since this is December, it sounds like the impeller. They should be replaced every several years.

Could also be a blockage in the powerhead. But I always carry on board a few feet of thick weed-whacker mono and coiled spring wire for cleaning out the 'pee port' or tell-tale cooling water discharge ports. Another thing in regards to blockages - if the water can't discharge, it can't feed in new cooling water!

FWIW my bros and I run a dozen or more OBs just between us and during any season and I'll take care of another few dozen or so, for my boatclub and other owners. I'd say on average, where cooling is suspect, cleaning the port works on more than half and then on the others, completely remove the cooling tube from the powerhead nipple and clean inside there. On just a few I've had to remove the LU and tip them upside-down and fill the heads with vinegar or Salt-Away and let them sit for a day. I have also used test barrels where the water was charged with Salt-Away or vinegar and would periodically run them and then let them sit to soak it.

Remember, these cleaners work while the motor is sitting, not running. I have always been able to clear blocked PHead passages by this method. And of course, none of that work precludes replacement of the impeller, which should be a must if you don't personally know the history of the motor. Also test and replace the thermostats and service the popitts if equipped. I see too many fail to service these, even on large (V4 and above) motors.

Since my Mercury 50 doubles as a dredge, (our tax dollars are used to dredge areas that are already deep, while waterfront property owners look at mud flats behind their houses at low tide) I know all about water pumps. I removed the plastic fitting and drilled a hole in the lower half of the cowling, so the cooling hose fits through there, since the little hole in the plastic fitting is subject to clogging from a few grains of sand.

I change my water pump at least once a year, sometimes twice a year, depending on how much dredging I have to do to get back and forth from my dock at low tide. Also, I carry a fuel primer bulb with a length of hose. Whenever the engine gets a clog, I stick the barb of the fuel primer bulb in the end of the hose from the cowling, and then proceed to backwash water through it, which clears it out, whether it's sand, weeds, or ground-up oyster shells.

Also, thermostats are bad for clogging with weeds and other debris. If you're operating in debris or grass-laden water, remove the thermostat. The engine will run a little colder and smoke more (if it's a 2 stroke) but you won't have as many overheats.

He doesn't know when the impellar was last changed, he bought it used. I'm thinking the impellar let go to but all the steam confused me (led me to believe it might have been a clog).
Anyhow... Thanks for the ideas guys

Djknyork said:

He doesn't know when the impellar was last changed, he bought it used. I'm thinking the impellar let go to but all the steam confused me (led me to believe it might have been a clog).
Anyhow... Thanks for the ideas guys

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Anytime I've seen steam it means water is flowing to the powerhead, but it doesn't fully circulate and exit (dumping the heat) so it cooks off ...

More reasoning to check the exit flow circuit of that motor.

Might be time to calm down a bit and take a breath!
When duck hunting you are going through some of the worst junk you can for an outboard. About half water and half vegetation.
This is pretty common for engines subjected to this.
First....put the engine back in the water after cleaning the intakes for the pump. If it pumps your duck season is saved.
Second. Watch the overboard indicator stream while in the thick stuff. When it goes away stop and back up to clear the intakes or shut down and clean them off by hand. Keep going and repeat as necessary.
Usually you will wind up a bunch of weeds in the prop anyway before overheating.
You can run an extended overboard indicator hose up through the cowling and along the side of the hull to the driver position so he can see the stream better. Have done that before and seen it done several times.

Ended up being a blown seal where the driveshaft comes through the water pump housing. Atleast that's what my buddy tells me. He put a whole new kit on last night.
Thanks for the help guys