2000 150hp Johnson overheating

[Redhunter]

A friend of mine has a 2000 150hp, he ran for about 20 mins @ 4200 RPM with no problem after that he kicked it up to 5200 and with in 3 min the alarm went off. He tryed once more and the something happens. Any suggestions?

[99yam40]

watch the gauges to see what is causing the alarm

And why post this in a Yamaha forum?
It still holds true though

[rodbolt17]

and some of the older OMC/BRP stuff also had a fuel vacuum switch.
but that would be before an MMI graduates time.
the OMC would go into RPM reduction if it was overheat.
no RPM reduction for oil or fuel alarm.

[Redhunter]

watch the gauges to see what is causing the alarm

And why post this in a Yamaha forum?
It still holds true though

I am a member of this Fourm and just trying to help a friend. Was just hoping with the Vast Experience on this Fourm I could get some ideas. Did not want to make Waves...

[99yam40]

I Hope Rodbolts post gave you some info you needed

[rodbolt17]

no waves.
but can you tell me if this is a 90* v6 or a 60* v6??
out of memory I cant remember when OMC changed.
the 90* had head gaskets, the 60* used orings.

[seahorse5]

An easy way to tell the crossflow 90° from the looper 60° is the location of the engine trim switch.

Loopers have the trim switch on the port side and the motor cover is held by 2 latches.

A crossflow has a stb. mounted switch and 3 latches on the cover



A 2000 model year 150 would be a looper.

High speed overheats on that particular engine are usually caused by thermostats sticking in their grommet seal, worn water pump parts, or deposit buildup inside the cylinder head casting. Do not overlook disturbed water flow from transducers or through-hull fittings within 14" of the engine centerline. Salt can lift the cylinder head orings and allow combustion gases into the cooling system in rare cases.

[Redhunter]

An easy way to tell the crossflow 90° from the looper 60° is the location of the engine trim switch.

Loopers have the trim switch on the port side and the motor cover is held by 2 latches.

A crossflow has a stb. mounted switch and 3 latches on the cover



A 2000 model year 150 would be a looper.

High speed overheats on that particular engine are usually caused by thermostats sticking in their grommet seal, worn water pump parts, or deposit buildup inside the cylinder head casting. Do not overlook disturbed water flow from transducers or through-hull fittings within 14" of the engine centerline. Salt can lift the cylinder head orings and allow combustion gases into the cooling system in rare cases.

Like I Said Vat Knowledge on This Forum

Thanks Rodbolt and seahorse

[rodbolt17]

and remember.
OVERHEAT goes into SLOW( Speed Limiting Overheat Warning) also known as RPM reduction.

NO rpm reduction for fuel or oil alarm.

[seahorse5]

Rodbolt brings up a good point.

It is the TEMP or HOT light that comes on with the alarm and the motor slows to 2500 rpm, right?

Or does the CHECK ENGINE light come on with the buzzer but the motor keeps running at speed?

If it is the CHECK ENGINE light then that is the vacuum switch activating because there is a ruel restriction somewhere in the boat most likely.

We need the whole story with details to be able to offer an accurate answer.

[Redhunter]

Good news help my friend change out the water pump and fix the problem. Old pump was pumping but just not enough it seems at the higher RPM's

Thanks Guys