proper prop installation

Brass

Delta even threw in some gratis beer coozies!

Pete, We used to lap horse shoes before the car came along.
(BTW we are only about 2 years apart)

This is a fantastic and helpful thread for sure Pete, Very kind of you to share the knowledge with us clowns. I got away with not lapping for over 25 years but I now know that was wrong.
One point on torqueing the prop nut.   30-35 pounds of torque is not very much.
Even small cars torque the wheel studs to 90 pounds torque so keep in mind how little 35 pounds is. Most of us have changed a tire on our cars and know how tight that is.
The prop nut is about 1/3 that tight.   An impact gun could blast that nut down to 150-250 pounds in a quick application of air power.   Using a 2x4 to tighten the nut?   Any water skier has plenty of grip in your hands to hold the prop with one hand while tightening the nut to 35 foot pounds.   If you need a 2x4 you are way too tight.
Using a crescent wrench on the nut, if adjusted properly I see zero issue using the adjustable wrench for this little amount of torque.   

I should follow up with my observation, in the old days before lapping changing a prop was really easy.   I never had to fight getting one off because they were installed badly and I did not know it. A lapped prop will need a tool to remove it every time, showing you did the job correctly and safely.
I also had the clank of the prop hitting the nut when put in reverse before I started lapping, that clank going into reverse should be a red flag for any inboard boater.
Pete"s advice should be listed as gospel on this issue.   Thanks again and I hope all the new guys get a chance to read Pete's advice.

New 422 installed. I am glad that I decided to change the prop this year as when I went to change the screw was loose and the prop just fell off the taper. I am thinking that I am fortunate that I did not have any trouble last season.

I lapped the shaft as mentioned in this thread and ended with a nice fit.

Here is a pic, Cleanup of underside of boat is needed!!!!!

I also need to do some serious trailer work in the fall.

Russ,
Water base will work just fine plus it's easier to clean up! The Prussian blue is optional as it's just a good indicator of high and low spots.

Suggestion - if your taking the time to lap the shaft above spend the extra bucks and get the correct sized wrench and sell the adjustable to those working on mastercrafts. Got to say I was very surprised to see such a tool in Pete's hand

That's good to know, thanks

IAughtNaut wrote: You're probably good...there's a lot of guys who have never lapped a prop and never have any problems. You hit the toilet 95% of the time and your toes are going to stay pretty dry.

Yes, there are plenty of people who have never lapped a prop but if you read this thread thoroughly you will understand that was with the old props and not the CNC machined props. Props used to be reamed but the CNC props are not. Yes, CNC is accurate but not to the extent of the greatest fit. Why do you think Morris tapers are ground? Why do you think Acme even recommends lapping.

Thanks fellas its getting there slowly

95%? Bolt it up and splash the damn thing already!

Tony - The grinding compound leaves a satin finish. I have not used the blue. I think the bogey is 90% cleanup.

Tony, I have found my own blood to be a suitable substitute...
It has gotten a little thinner after 30 years in S Florida and seems to flow nicely over machined surfaces...

Fitted my new 1442 the other day. Checked it with blue compound almost perfect contact on taper. Still gave it a quick lap with the cutting compound.

ACME are now putting a note in with their props to check the taper fit.

4mor wrote: I have never "blued" the shaft or for that matter, even cleaned it. Am I doing something wrong or am I just lucky .

Blueing is an option. It's just an indicator of high and low spots. It's the lapping that is key to matching the taper. Yes, many have gotten away without lapping. Most have been lucky but there are others who have lost props.