Still struggling to set up my Tohatsu 9.8 - Page 2

Max... · 11 September 2012, 17:33

Quote:

Originally Posted by lightning

I tightened the nut until the pin could be fitted, but it's only just over hand tight.

This was the same with the original prop.

I'll check the manual for prop nut tightening torque when I get home, but it's not going to come loose with that split pin in place.

Should there be a washer that goes on before the prop is fitted?

Read my post above! You need to add a shim (trial and error to add the correct thickness of shim/washers that allows the prop to be fully tightened and leave the hole in the right place to line up with the hole in the spindle).

captnjack · 11 September 2012, 18:47

Quote:

Originally Posted by Max...

Read my post above! You need to add a shim (trial and error to add the correct thickness of shim/washers that allows the prop to be fully tightened and leave the hole in the right place to line up with the hole in the spindle).

What are you trying to accomplish??

Prop nut torque is not that critical. The nut is tight and the pin fits. Its not coming loose or going to vibrate and damage the shaft splines.

Max... · 11 September 2012, 20:12

Quote:

Originally Posted by captnjack

What are you trying to accomplish??

Ehhh?!

What a daft question. Maybe I'm 'trying to accomplish' helping the OP get his prop fitted properly rather than 'hand tight'.

captnjack · 11 September 2012, 20:38

Quote:

Originally Posted by Max...

Ehhh?!

What a daft question. Maybe I'm 'trying to accomplish' helping the OP get his prop fitted properly rather than 'hand tight'.

His prop is fine. Its not coming off or going to damage the shaft the way he's installed it.

Mucky about with shims so he can tighten the prop accomplishes nothing and is a distraction from his actual problem which is engine and transom height.

lightning · 11 September 2012, 21:01

I appreciate all the advice. The wooden block has raised the engine 2cm and allowed the upper plate to be above the water, the splashback has pretty much gone.
As for the prop l looked at the manual online and all parts are present, no washers missing. The manual does not give a torque for the nut so l just tightened it enough not to be loose, then fitted the split pin.

Poly · 11 September 2012, 21:07

Quote:

Originally Posted by Max...

Ehhh?!

What a daft question. Maybe I'm 'trying to accomplish' helping the OP get his prop fitted properly rather than 'hand tight'.

Its not hand tight - its "just over hand tight". I can't find a torque setting for it (I note the Tohatsu manual online doesn't provide one - simply referring to "ensure tight" and makes no mention of shimming). This service manual has no values for the 9.8 (Tohatsu Service Manual For1 2cyl 2stroke05ver) (page 6-3).

Locozodiac · 11 September 2012, 21:22

Just place a wooden block under cav plate to stop prop from rotating, adjust nut with hand tight and then with a wrench rotate nut CC untill next notch on nut is found so to insert split pin through shaft. No shim is needed as there is a big washer between prop body and nut. Grease well shaft with water resistant grease before assembying back, will be much more easier to remove in future.

Happy Boating

Max... · 11 September 2012, 22:08

Guys, it doesn't matter if it's a Twatsoo prop or whatever, standard (and *correct) engineering procedure is to torque the nut to the correct level (certainly not just hand tight). IF that means the holes don't line up you need to add a thin shim (aka washer!) to allow this to happen. You don't just leave it hand tight - the pin is not to hold the prop on as a failsafe it's to stop the nut loosening full stop.

Poly · 11 September 2012, 23:14

Quote:

Originally Posted by Max...

Guys, it doesn't matter if it's a Twatsoo prop or whatever, standard (and *correct) engineering procedure is to torque the nut to the correct level (certainly not just hand tight). IF that means the holes don't line up you need to add a thin shim (aka washer!) to allow this to happen. You don't just leave it hand tight - the pin is not to hold the prop on as a failsafe it's to stop the nut loosening full stop.

There is no "correct level" twatsu don't provide one there is a "-" in the table for that size of engine! I've never known a shim be required (I've only dealt with small outboards using OEM props) and there is no mention in either the owners manual or the service guide. I believe Locozodiac describes the 'normal' procedure when there is no spec given. Finger tight then continue to tighten until you can fit the pin.

Downhilldai · 12 September 2012, 00:05

No need for shims under the prop nut - it's a splined shaft.

lightning · 12 September 2012, 09:38

Yes l took off the thrust washer and it's as you say a splined shaft with the end tapered out. The thrust washer is plastic with a splined metal sleeve and a thin metal washer where it contacts the rear of the prop.
If you tightened the nut to anything more than nominal torque it would damage or distort the plastic thrist washer.
The manual should really give this information.

m chappelow · 13 September 2012, 12:40

Grease the splined shaft ,
Slide on the thrust washer,,,,, make sure it's the right way around ,
Slide on the prop,
Slip on the plane washer ,
Finger tighten the castled nut,
Then nip up the nut slightly ( about 8 th of a turn or so or until the split pin can be pushed right through ,
If you use a socket or the box socket supplied with the engine you should only need to use it in a clenched fist and normally shouldn't need to use a bar or screw driver or extension lever on it to tighten ,
Prop doesent want any forwards or backwards movement on the shaft ,,

I just looked in the owners manual and it doesent give a detailed explanation but just a parts diagram ,, suppose they want you to take it to a dealer lol.

lightning · 13 September 2012, 18:55

Thanks, that's what I ended up doing after I took a look at the parts.

captnjack · 13 September 2012, 19:00

So is the cativation / engine height issue solved?

lightning · 13 September 2012, 22:28

Yes the cavitation no longer occurs, the engine is now running very well on the boat. The splashback has been greatly reduced by raising the engine 2cm (the most it will raise without the clamps touching the ridge on the mounting plate) using a piece of wood.

Currently I'm swapping between the two propellers trying to decide which is best for this boat.
But I cannot test it at full throttle as there's a speed limit on the estuary where we are staying in Cornwall. To be honest it'll be next year before I get back to Scotland where many Lochs have no speed limit.