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I started doing all the regular maintenance on my
Honda 50hp (change oil, oil filter fuel filter, plugs,
gear oil) and when going to warm it up, with the
hose hooked up to the "earmuffs" I noted that no
water was coming out of the side as usual.

I checked for any obvious blockages, etc. and nothing
seemed amiss.

Does this mean the impeller needs replacing? Could
there be a more obvious/simple reason?

If the impeller needs replacing, is this something that
is easily done myself or is it a major job?

Run a piece of wire through the bleed tube - often insects make their nest up there and clog it up. If the wire goes in all the way and it doesn't start flowing, then you're probably due to have the water pump impeller replaced. It's not a bad job - you have to drop the lower unit. Most manufacturers recommend replacing the impeller annually, but I've seen them last for many years... kinda depends on how nasty the water you run in is, and whether it's salt or fresh. Best to have a shop manual before you undertake the work, of course - they are readily available from several on-line sources - Amazon might even have it.

Do a search on here (see link at top of page) for "water pump impeller" (click 'search all words' button) and you'll likely find other past discussions that will be useful.

kmclemore wrote:Run a piece of wire through the bleed tube - often insects make their nest up there and clog it up. If the wire goes in all the way and it doesn't start flowing, then you're probably due to have the water pump impeller replaced. It's not a bad job - you have to drop the lower unit. Most manufacturers recommend replacing the impeller annually, but I've seen them last for many years... kinda depends on how nasty the water you run in is, and whether it's salt or fresh. Best to have a shop manual before you undertake the work, of course - they are readily available from several on-line sources - Amazon might even have it.

Do a search on here (see link at top of page) for "water pump impeller" (click 'search all words' button) and you'll likely find other past discussions that will be useful.

Thanks for the suggestions.

I went and grabbed a plastic trash can and filled it with water, to be
sure that the engine was getting all the water it needed (maybe the
"earmuffs" weren't working properly). I then disconnected the output
water hose that connects to the little valve in the engine case and
was able to blow through it easily and get lots of bubbles coming out
of the lower intake vents. So nothing seems to be clogged.

I then ran the engine again, leaving that hose disconnected, to see
exactly what is going on, and noted occassional, sporadic, but minimal
spurts of water coming out, and once the engine warmed up, some
"almost" steam (warm air with heavy condensation) coming out.

So I'm guessing the impeller is shot.

Does anyone know where I might find the service manuals online, or
at least the exploded parts diagrams?

I ran our 50 Honda the other day before heading to Florida with the "mickey mouse" ears. I worried it was not pumping also. However, it finally started the stream and ran fine for about twenty minutes. They may take a while to get started ????? I hope nothing is wrong. I just thought it must have a thermostat or something. Now I'll have to check my service CD when I get home Monday.

Retcoastie wrote:I ran our 50 Honda the other day before heading to Florida with the "mickey mouse" ears. I worried it was not pumping also. However, it finally started the stream and ran fine for about twenty minutes. They may take a while to get started ????? I hope nothing is wrong. I just thought it must have a thermostat or something. Now I'll have to check my service CD when I get home Monday.

From now one, I'm going to use a trash can, just to be absolutely
sure that it's getting all the water it needs and I'm not shortening
the life of the impeller, or motor in general.

I never did much trust those "earmuffs" to work as well as a
full immersion...

I've always used ear muffs on my Honda 50 and have had only once or twice a problem with no water coming out of the water outlet. The problem has always been the outlet hose was clogged and rolling the hose between my fingers would usually remove the blockage (salt has a tendency to buildup in this line even though I flush the motor every time after using). I usually change the impeller myself annually but have let it go as much as two years between changing.

My point is, if you don't see water coming immediately out of this outlet line assume the worst (engine isn't getting any water) otherwise you could be in store for an expensive engine repair. Even running only a minute or two the water coming out of this hose is noticeable warmer than the inlet temp and is providing much needed cooling for the motor.

Changing the impeller is quite easy and I would also would recommend a manual.

Good luck!

Just a followup. Turned out the impeller was indeed bad. Replaced it,
and the motor is peeing nicely.

BTW, the fiberglass tub that the stock cooler sits in is perfect for
running the motor in the driveway. It's just the right height and
ensures that there's plenty of water cooling the engine.

Water pumps are one of OUTBOARDS biggest problems...One of these days, the maunfacturers may design a motor with a pop in pop out pump that can be easlily accessed...but I'm not holding my breath.
Most big motors require specia-lised tools...just pay the mechanic...
P.S. I put a hyphen in the 's' word because of a spam warning...a word not allowed...C.I.A.L.I.S not sure what it means, but its not allowed...And my word contains the same letters in the same order.

There are no special tools needed for changing the impeller on a Yamaha 50.

It's easy enough - basically just involves undoing a few bolts and putting it all back together again - just follow the instructions.

For repair manuals have a look here

Mike