Impeller question

[tom from mass]

Before dropping lower unit to change impeller, is it a good idea to start engine,shift into forward and then shut off engine while in gear?
Is this so that when re-installing lower unit the prop can be turned by hand to help line up the splines?
Thanks,
Tom from Mass

[boscoe99]

Just leave the shifter in neutral. Drop the lower unit and replace the water pump. Do want you will to the drive shaft. Just don't mess with the shift shaft. It will go back together properly phased.

[tom from mass]

This is for a 2005 150 four stroke. A video on u-tube by Jamestown Marine suggested shutting off the engine while it is in gear but didn't elaborate why.

[boscoe99]

I can only guess that whoever did the video screwed up one time and got the shift handle and the lower unit out of synch with one another. Certainly there is no Yamaha advice about doing it this way. The SM procedure has the propeller being removed first so it won't be there to turn the propeller shaft if that is what the intent is.

It really does not matter however. Leave it is neutral. Leave it in forward gear. Leave it in reverse gear. Shift the lower unit while it is removed or not. Main point is that whatever gear the shift lever is in at the time of installation then the lower unit needs to be in that gear as well.

Now if someone fails to get the shift shaft aligned with the shift rod it won't matter anyway since the motor won't be shiftable when the lower unit is reinstalled.

By the way, I challenge anyone to try and install an F350 gear case by themselves while at the same time turning the drive shaft via the propeller shaft to get the drive shaft to align with the crank shaft. With or without a propeller being installed.

[rodbolt17]

challenge accepted.
opponent beaten.
I do several a year.
dunno who came up with that driveshaft extension housing using studs but the should be drawn and quartered BEFORE being shot.
I did one about 2 weeks ago.
at 140 pounds or so that case is a handful for me.
I hate F V8 motors but the money is nice.

I have gotten so I can change the cyl block and head assy' in less than 19 hours though.
between rotor failures and cyl heads freezing and cracking I am getting quicker at it.

just finished an F250 with a bent rod, Yamaha sent the guy a powerhead and 2 cylinder heads.

[TownsendsFJR1300]

This is for a 2005 150 four stroke. A video on u-tube by Jamestown Marine suggested shutting off the engine while it is in gear but didn't elaborate why.

I have the same engine, just an 06.

Leave it in neutral when pulling it.

Also, depending on if you have a long or short shaft, the long shaft has a bushing in the mid section that supports the driveshaft. You'll see a shiney area in the middle of the shaft (besides the extension on the lower unit).

Make sure you use Yamaha waterproof Marine grease in this area, NOT automotive wheel bearing grease, or it will squeal (chirp actually) after some time. Its the same grease you'd use on the splines/ prop, when re-assembling,

[rodbolt17]

IF it uses studs on the midsection extension I will either shift it to fwd while someone rotates the prop OR have someone rotate the flywheel while I am reassembling it.
motors without studs I leave in N.

[TownsendsFJR1300]

I've always left the extension bolted to the mid section. My LU uses bolts to bolt to the extension. I do have a extra set of hands re-assembling so should the shaft need rotating slightly, it can be done right there

The lower unit alone would be pulled with the prop off. A little lighter (SS prop) and that shaft gets lubed right away..

Just looked at it, ALL the fasteners are bolts, Not a stud at the extension or LU anywhere...

[99yam40]

SS props can be very sharp
wrangling a large lower unit with knives hanging on the bottom end causes blood to get spilled.
But I guess some good leather gloves would give some protection to the hand/fingers.

Best to remove prop before dropping lower, and putting back on after lower is reinstalled

[rodbolt17]

some 25 and 30" motors use STUDS to retain the gearcase.
studs suck as once you start the gearcase up the studs you cant rotate the case to align the shaft.
this means that typically to line up the drive splines either the crank must be rotated or the drive shaft.
I use blue masking tape to hold the extension to the mid section.

[TownsendsFJR1300]

some 25 and 30" motors use STUDS to retain the gearcase.
studs suck as once you start the gearcase up the studs you cant rotate the case to align the shaft.
this means that typically to line up the drive splines either the crank must be rotated or the drive shaft.
I use blue masking tape to hold the extension to the mid section.

Ok, I know the studs would be stronger but yes, that makes sense otherwise you'd have to lower the LU a bit to slightly rotate the drive shaft.


Also, re you last statment, they use One super long stud?

There isn't a separate stud/nut,washer to hold the extension to the mid section??

[rodbolt17]

yep, it adds the nessasary 5".
some bolt the mid section extension and some simply use studs.
same mid section,longer water tube,shift shaft and drive shaft.

[TownsendsFJR1300]

Interesting. Sounds like an additional PIA..

Somewhat minor but another part to line up... Tks..