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SoCal205
01-21-2008, 04:04 PM
I recently bought a new prop on the install directions it says to have 60% contact. My mastercraft manual says 70% contact, it also says to use a compound called persain blue and a grinding compound. So my question is where can I find these compounds? Or does anyone have any other suggestions.

CRAIGTHEMAN
01-21-2008, 04:09 PM
for years iv been switching my prop on my boat and all i do is get the old one off,put the new one on and get the nut somewhat tight than throw the cotter pin in...hasn't failed me yet

TMCNo1
01-21-2008, 04:30 PM
This thread may give you some information about Prussian Blue. Prussian Blue also known as Engineers Blue and Valve/Grinding Compound can be found at most auto parts stores and where machinists/metalworkers get their supplies. Here is a more in depth explanation of it's use, http://en.wikipedia.org/wiki/Prussian_blue and here http://en.wikipedia.org/wiki/Engineer%27s_blue .

Sodar
01-21-2008, 04:54 PM
SoCal... all they are trying to do with the substance recommended is keep the dissimilar metals away from one another (stainless & nibral/bronze). A few years ago, when I worked for a local High-Performance boat shop, the head mechanic recommended this (http://www.wholesalemarine.com/p/92-802865Q02/Quicksilver+Special+Lubricant+101.html). It is a teflon based waterproof grease. The stuff is TOUGH and not cheap, but a little goes a very long way. Anyways, after seeing the conditions that this grease held up in, I am sure it will provide the same benefit as those you listed, but be a little easier to find!

TMCNo1
01-21-2008, 05:10 PM
SoCal... all they are trying to do with the substance recommended is keep the dissimilar metals away from one another (stainless & nibral/bronze). A few years ago, when I worked for a local High-Performance boat shop, the head mechanic recommended this (http://www.wholesalemarine.com/p/92-802865Q02/Quicksilver+Special+Lubricant+101.html). It is a teflon based waterproof grease. The stuff is TOUGH and not cheap, but a little goes a very long way. Anyways, after seeing the conditions that this grease held up in, I am sure it will provide the same benefit as those you listed, but be a little easier to find!

I always apply some Lubrimatic Marine Corrosion Control and Trailer Wheel Bearing Grease to the shaft, key slot, key and inside the prop hub before I install the prop. You would be surprised how much of it is still there when the prop is removed, even though it took a prop puller to get the prop off.

JLeuck64
01-21-2008, 06:05 PM
Here is a simple way to check the contact between your prop and shaft.

WITHOUT the new key installed in the keyway, slide the prop onto the shaft until it stops. Now mark around the shaft, with a Sharpie, to indicate how far up taper the prop fits.

Install you new key into the keyway and install the prop and nut as per directions. Now, in it's final resting position the prop should at least come back to your indicator mark, or it may just start to cover the mark. This is good, you don't have to worry about the key shifting causing an interference between the fit. Which is what we are most concerned about. The 60% contact sounds more like a racing/High perfromance concern to me. I would bet if you checked it with Prusian blue it would be fine anyway...

TMCNo1
01-21-2008, 07:34 PM
It has to do more with the mating of the shaft and prop hub surfaces, than how far the prop goes up on the shaft. I would think, that since it is in the owners manual there is a reason for it to be there, just like the instructions for changing the engine/transmission oil and related filters, greasing the steering fittings, shaft alignment, among other maintenance items to be addressed during ownership, but.....................:rolleyes:

Maybe Eric from OJ will give us some advise on this subject.

coz
01-21-2008, 07:43 PM
I recently bought a new prop on the install directions it says to have 60% contact. My mastercraft manual says 70% contact, it also says to use a compound called persain blue and a grinding compound. So my question is where can I find these compounds? Or does anyone have any other suggestions.


I just asked this same question 2 days ago and these great folks at TT squared me away, looks like you got the same treatment :D Thanks again on this post.

Sodar
01-21-2008, 07:45 PM
...I would think, that since it is in the owners manual there is a reason for it to be there....:rolleyes:

I tend to take Mike's stance. Seems like alot of the stuff in the manuals has more to do with CYA, than actual necessity.

Throw the manual away...no reason to hold on to a book of suggestions...wonder why they waste the paper on printing those things anyway?:confused:

http://tmcowners.com/teamtalk/showpost.php?p=447375&postcount=6

coz
01-21-2008, 07:48 PM
SoCal... all they are trying to do with the substance recommended is keep the dissimilar metals away from one another (stainless & nibral/bronze). A few years ago, when I worked for a local High-Performance boat shop, the head mechanic recommended this (http://www.wholesalemarine.com/p/92-802865Q02/Quicksilver+Special+Lubricant+101.html). It is a teflon based waterproof grease. The stuff is TOUGH and not cheap, but a little goes a very long way. Anyways, after seeing the conditions that this grease held up in, I am sure it will provide the same benefit as those you listed, but be a little easier to find!

This is a mecury product and the stuff works great on all kinds of applications. :)

SoCal205
01-22-2008, 06:16 PM
thanks everyone for all your help

88 PS190
01-22-2008, 07:00 PM
It can be amazing to see the fit.

If your prop shaft is splined there is no need to pay attention to this, but if its keyed you might want to consider it.

Prussian blue is a machinist dye that allows you to see contact, its basically a paint that disappears when there is contact. So ideally the prop will mate to the shaft a certain amount.

Lapping compound such as valve grinding paste is then used to improve fit by grinding both surfaces at once.

It is perhaps a bit of a perfectionist goal.