1997 90 hp Question

[Yamadoggie]

looking at a 1997 90 HP inshore series motor. Sinc ei am new to these motors did they have a safety feature to limit RPM based on temp running hot?

Also I assume normal operating temp for these is same as other outboards, probably no hotter than 160F? Most overheat sensors go off at about 170F.

thanks

[boscoe99]

I am not sure what an inshore series Yamaha motor is. Never heard of one.

Of the Yamaha 90 HP two strokes that I am familiar with the 1997 model uses a thermoswitch that will close when the temperature or the switch is between 183 and 194 degrees F. Normal operating temperature obviously will be below this value.

The thermostat will begin to open at ~126 degrees F and will be fully open at ~140 degrees F. It is normal for a motor to run hotter than the fully opened position of the thermostat.

If and when the motor were to get too hot (thermoswitch closes) the alarm should sound and the motor should go into RPM reduction mode. If and when the alarm sounds the motor should be stopped immediately. Otherwise it can be damaged. Some seem to think that if it is in the RPM reduction mode that it can be operated. They do so at their own peril.

[Yamadoggie]

so thi smotor does have an RPM reduction feature? That is what I needed to know. It is a friends motor an di have no clue whether he shuts it down or not.

Thanks

[cpostis]

I believe you have a model B90T*RV?

Jethro (Boscoe), "B" is an "Inshore Series" engine.


Per service manual LIT-18616-02-05:

T-Stat opening 118-126 F
T-Stat full open 140 F
T-Stat Lift 3mm (0.12")

Thermo Switch on 183-194F
Thermo Switch off 140 165 F

[boscoe99]

The marketing designations mean nothing. Offshore, Inshore, SHO, Saltwater Series, etc. are all just fluff.

What is needed, what is always needed, is the complete model identity.

If this is a B90TLRV then that is what it is.

People get hung up on the marketing gizmo doo doo. Think they can't take an inshore motor offshore. Think they can't take a saltwater series motor in fresh water. Think an offshore motor can't be use inshore.

It is Yamaha madness I suggest.

[robert graham]

so thi smotor does have an RPM reduction feature? That is what I needed to know. It is a friends motor an di have no clue whether he shuts it down or not.

Thanks

If his motor is running hot sometimes then he should check and replace the water pump, thermostat and pressure control valve....easy and cheap preventive maintenance that should be done every year or 2 or 3, depending on use....

[99yam40]

If and when the motor were to get too hot (thermoswitch closes) the alarm should sound and the motor should go into RPM reduction mode. If and when the alarm sounds the motor should be stopped immediately. Otherwise it can be damaged. Some seem to think that if it is in the RPM reduction mode that it can be operated. They do so at their own peril.

Yamaha could have just shut the motor off when low on oil or overheated alarm comes in, but this may have caused people and their boat to be at risk of something very bad happening depending on where they were at when this happened.

So they allow the motor to still run at reduced RPMs hoping they could get out of dangers way before shutting down ,risking the motor if they keep going too long.

if the buzzer did not function as it should the RPM reduction will also signal there is a problem the needs your attention.
this is why gauges that can indicate what problem the motor is having is always a good idea to have

[boscoe99]

I agree that if one would be in imminent danger due to turning the motor off, and the alternative is to destroy the motor to save the boat and lives, then do what needs to be done.

My point was that all too many think it is just fine to continue to run the motor if and when it is in the RPM reduction mode. Ain't so.

[boscoe99]

so thi smotor does have an RPM reduction feature? That is what I needed to know. It is a friends motor an di have no clue whether he shuts it down or not.

Thanks

Why would it not have RPM reduction in the event of a problem?

Here is a link to the owner's manual. See what it says. Start on page 2-18.

http://www.yamaha-motor.com/assets/s...-02-90_606.pdf

[throrope]

so thi smotor does have an RPM reduction feature? That is what I needed to know. It is a friends motor an di have no clue whether he shuts it down or not.

Thanks

Unless your friend is giving it to you, I'd pass. After 20 years anything could be amiss and repairs add up quick. Getting upset with him for destroying a "perfect" outboard is an easy way to loose a life long friend.