'97 C90 Yamaha Over Heat Alarm

msd58

Petty Officer 1st Class
Joined
Feb 14, 2003
Messages
280
Been running my 90 HP all weekend long. When rpm's are 4300 and up for a mile or so the temp alarm sounds. After a few mins of sitting with motor off the next start up the alarm shut down. Motor runs all day with no problems at 3600-3900 all day. What's the problem?
 
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Capt Ken

Commander
Joined
Jul 30, 2002
Messages
2,269
Re: '97 C90 Yamaha Over Heat Alarm

Hmmm, let me gaze into my crystal ball. I see a replacement of a water pump in your future.
 

99yam40

Fleet Admiral
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Sep 7, 2008
Messages
8,851
Re: '97 C90 Yamaha Over Heat Alarm

Capt Ken,
I have been telling them we do not have those crystal balls that let us know what the problem is, and now you say some have them.
this could get confusing:eek:
 

msd58

Petty Officer 1st Class
Joined
Feb 14, 2003
Messages
280
Re: '97 C90 Yamaha Over Heat Alarm

Not trying to sound stupid here but the waterpump is no more than 2 seasons old. That included this season. Just in case its the not water pump could be something else?
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: '97 C90 Yamaha Over Heat Alarm

I have seen vanes break off of impeller less than a year old and others that last for many years and work well.
But it would be the 1st thing to look at along with the housing
Then thermostat and water passages
and check over heat switch to make sure it operates with in spec
 

Capt Ken

Commander
Joined
Jul 30, 2002
Messages
2,269
Re: '97 C90 Yamaha Over Heat Alarm

99yam40, you didn't get the required crystal ball that Yamaha sent out?
Oh geesh, the water pump is only two seasons old. Well of course its not that! Yamaha maintenance requires the waterpump to be inspected yearly and I've seen them go bad within less than a season of use. I've seen owners do stupid things and they go bad within a couple of weeks.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: '97 C90 Yamaha Over Heat Alarm

Well I need to contact Yamaha and check on a crystal ball.

All it takes to hurt an impeller is to turn motor over without water in the pump for lube, if vanes are stuck it will rip them.
And then there is sand and shell that can be sucked in that acts like sand paper on rubber,

saw weeds plug off intake and turn rubber impeller in to a melted blob, suprized me but it still pumped water at higher RPM but not much at low RPM
 

msd58

Petty Officer 1st Class
Joined
Feb 14, 2003
Messages
280
Re: '97 C90 Yamaha Over Heat Alarm

I replaced t-stat, water pump & pop off valve (PCV). The problem has seemed to go away but sometimes when I start up motor and during warm up and while I loading the boat up the temp alarm goes off. I shut it down few a few minutes and then its fine. What else is there to replace?
 
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