Flywheel Torque 1997 Yamaha 150hp

[RogerTammy77]

We have had to replace the flywheel on our 1997 Yamaha 150hp.outboard. Its a C150TXRV. Does anyone know the pounds of torque we should tighten it to?

Thank you,
Tammy

[cpostis]

Your motor s/b a "pre-mix" motor (no oil injection), correct. If so, the M20 nut s/b torqued to 120 foot pounds. A flywheel holder will be required to tighten the nut to this specification. I built mine.

You should purchase a manual on this motor. Well worth the money!

See the link:

LIT-18616-02-01 YAMAHA C,S,L,P,D150/S,P175/

[boscoe99]

140 pound-feet is the specified torque value.

[cpostis]

140 pound-feet is the specified torque value.

Boscoe, is this wrong from Yamaha Service Manual for C150X.150X.S150X.L150X.P150X.D150X.S175X.P175X.200 X.S200X.L200X.P200X.LIT-18616-02-01?



A "C150TXRV" is a "pre-mix" motor, is it not?

Please confirm

Thanks!!

[boscoe99]

Confusing. But then this is Yamaha data we are talking about.

OP says he has a 1997 C150V model year motor.

SM 02-01 is for a 1999 C150X model year motor.

I got my data from SM -01-87 which covers a C150W (1998) model year motor.

I checked SM -01-41 which covers a C150U (1996) model year motor.

The manuals don't all agree with the flywheel torque value. However, the same nut and same crankshaft are used for 1996 through 1999 C150 models. So wouldn't the torque specs be the same?

90170-20137-00 YAMAHA NUT,HEXAGON

6G5-11411-00-00 YAMAHA CRANKSHAFT

When it comes to torquing the flywheel nut I would use the higher torque value just to be on the safe (IMO) side.

Another anomaly I noted is that your SM does not indicate to lubricate the threads of the nut with engine oil. A different SM says to do this.

[robert graham]

I guess that loose flywheel nuts is not a generally frequent problem but wonder why some type of locking tab is not used?....sorta like the cotter key on the prop shaft or lock washer/tabs on some wheel hub nuts or similar?....

[TownsendsFJR1300]

At 125 minimum its NOT GOING anywhere.

Its on a tapered shaft making it even more secure..

Per my Yamaha shop manual, unless specified otherwise, the threads should be CLEAN AND DRY.

My flywheel nut is torqued DRY

*Lubed THREADS will yield a higher actual torque value.*.

[cpostis]

Matter of opinion Boscoe.

I found yet in another manual ALMOST the same specs that I quoted earlier. The exception being for a oil injected motor to be 140 foot pounds as compared to 137 foot pounds. This manual (NOT Genuine Yamaha) is supposed to cover 1997 -2003 motors.

Don't know if there is a difference between flywheels, but the part # for rotor assembly (flywheel) for the C150V (Pre-Mix) is:
6G6-85550-01-00

For same year S150V (Oil Injected) is:
64D-85550-00-00

I'd stick with the 120 foot pounds for the op's question and answer. Again, matter of opinion..
Thanks!!

Hope we didn't confuse you more RogerTammy!

[boscoe99]

I guess that loose flywheel nuts is not a generally frequent problem but wonder why some type of locking tab is not used?....sorta like the cotter key on the prop shaft or lock washer/tabs on some wheel hub nuts or similar?....

Damn good question. Although not rare the flywheel nuts will come loose from time to time. It can make a mess of things. Flywheel destroys the stators, itself and sometimes the crank shaft.

For want of a lock tab the nut was lost. For want of a nut the flywheel was lost. You know the rest.

[boscoe99]

The good thing about Yamaha manuals is that they are so ambiguous and incomplete that anyone can read whatever they want to read out of the book.

120 pound-feet, 137 pound-feet, 140 pound-feet, lubricated with engine oil, no oil used, it matters not a wit to me.

I report. You decide.

[cpostis]

The good thing about Yamaha manuals is that they are so ambiguous and incomplete that anyone can read whatever they want to read out of the book.

120 pound-feet, 137 pound-feet, 140 pound-feet, lubricated with engine oil, no oil used, it matters not a wit to me.

I report. You decide.

You got some BIG FEET Boscoe!

[boscoe99]

I guess so as to not confuse the OP we should have simply said to use the torque value that is specified in his genuine Yamaha service manual and let it go at that.

[99yam40]

sounds like no one has a 1997 manual to look at

[pstephens46]

Are we worried than 140 will damage something? Doubt it. My F150, I do believe, requires 199 lb ft. About a 36mm socket. I'll borrow a good air wrench if ever needed.

[robert graham]

Wonder if a violent prop strike would tend to stop rotation of crankshaft quickly enough to loosen that prop nut?...or even shear a flywheel key...if they have a key?...