[Rhodes22-list] Yamaha (non) cooling system.

[Michael D. Weisner]

Robert,

Sounds like you need a new mechanic!!

Cooling pump impellers do fail.  Interestingly, the more they are used, the 
longer they seem to last.  They usually fail at season startup because they 
adhere to the pump housing during dry season.

If the system still doesn't pump correctly after impeller replacement, look 
for a leaky pump due to lower unit seal failure.  The seal should be 
replaced when the impeller is changed, prior to lower unit assembly to 
engine (the "kit" includes the seals, see 
http://bpi.ebasicpower.com/pc/MAL9-48600/OB-YAMWP/Kit,+Water+Pump+Repair,+Yamaha+9.9-15+HP

Poor mechanics do not usually have gasket so they figure it is still usable 
and you have a leak.  If the line was "occluded" look for crud that was not 
properly cleaned out during initial service activity such as gasket/seal 
material trapped in line.  Most common problem which requires cooling tube 
replacement is improper reassembly of lower unit, not fitting tube into 
recess and forcing the lower unit into place, kinking the tube.  At this 
point a simple job becomes fairly expensive.

BTW, the standard Yamaha thermostat has a "weep hole" to permit flush water 
to circulate and drain from motor, I think.  I do not think that you need to 
drill any additional holes.

Mike
s/v Shanghai'd Summer ('81)
Nissequogue River, NY

From: "Robert Fuller" <Bobandsandy at tampabay.rr.com> Sent: Monday, November 
03, 2008 4:11 PM
> Rare post from dedicated reader :
> I have little mechanical ability and paid a free-lance mechanic to
> change the impeller on my Yamaha 9.9 with a total of less than 75 salt
> water hours on it after 2 years. Rapid onset of problem. Impeller was
> fried.  Still didn't pee right and today we found the cooling tube
> running from the lower unit up thru the oil pan was more than 50%
> occluded by a lining of soft corrosion (also extending on up towards
> the motor head).  He says the basic problem is yamaha uses substandard
> aluminum  in the oil pan (and he has seen pans expand and burst
> through motor housings).
> I flush the motor religiously for a timed 10 minutes after every short
> use.  Mechanic further claims the thermostat can cause flush water to
> remain in motor rather than drain and that this can be remedied by
> drilling a small vent thru thermostat.
> I have never seen this problem reported in several years of reading
> posts.  Does it make sense to anybody?  Other thoughts?  Especially on
> preventing recurrence?
> Lower unit and powerhead currently in his shop where he plans to check
> functionality of water pump and see if I blew head gasket. (back
> pressure then impede water flow).
> Bob in Cortez, Fl.
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