Bravo III props - what is the difficulty for removal?

wish2fish

wish2fish

Active Member
Dec 19, 2006
4,278
Locust Creek, Ohio River mm 433
Boat Info
2003 220BR
Engines
5.0 MPI
Last year my props got some scratches on them from mooring in the shallow water. While they dont' look like they are bent I would like to remove them and take them to the prop shop for checking/fine tunning.

So how hard are they to remove and what do I need to pay attention to when removing and replacing?
 
I'm watching this because I want to know too.
I know I need to get the Uber-Wrench for the two different sized prop nuts, but I'm interested to hear the how-to's as well.
 
They are simple to remove but you really need a prop wrench to get the rear one off. Here is a link to the place I bought mine.

http://www.properthing.com/models.html

First you remove the prop anode with a socket. Next, get yourself a 2X4 and wedge it between the prop blade and the cavitation plate to keep the blades from turning. Remove the nut on the shaft for the outer blade and slide the prop off. This gives you access to the nut on the rear prop. Using the prop wrench remove that nut and slide the rear prop off. Pay special attention to how the various spacers are used on the shaft so you know how to reassemble. You will also need to relube the prop shaft as well when you reassemble. Your dealer can supply you with the correct grease.
 
Make sure you put them back on out of phase.

One prop – have a blade straight up.

Second prop – have a pair of blades as far away from straight up as possible.

I’m dong a terrible job explaining this. Hopefully someone can do better.

Your goal is to install them so two blades are never straight up at the same time.
 
Presentation said:
Make sure you put them back on out of phase.

One prop – have a blade straight up.

Second prop – have a pair of blades as far away from straight up as possible.

I’m dong a terrible job explaining this. Hopefully someone can do better.

Your goal is to install them so two blades are never straight up at the same time.
Click to expand...

Good point Doug and one I have should have remembered.:smt021

When you put the props back on you need to position them so that as the props are spinning you don't have a blade from each of the two props crossing under the cavitation plate at the same time. This is generally referred to as "timing the props". The reason you do not want to have the inner and outer prop blades to cross under the cavitation plate at the same time is because it can cause a slight vibration and a loss of top speed as well. It's a simple thing to time your props and all you need to do is mount the props in a clover leaf overlap position which I'll explain as follows. First you put on the rear prop and tighten down the nut on the rear prop. (I will also mention that your manual will give you torque specs for the props and if you use the wrench from Properthing it has a place to mount your torque wrench. Having said that I never use a torque wrench myself and I never have seen a tech at our dealer use one either.) Once the prop nut is tight, rotate the rear prop so there is one blade pointing straight up right under the cavitation plate. Next, slide the outer prop in place with one blade pointed straight at the ground. With both blades in this position they will look like two cloverleafs that overlap each other. When they are in this position, if you spin the blades you will see that you never have a situation where a blade from both props comes under the cavitation plate together. The props are now "timed" properly. Snug down the outer prop nut then reattach the prop anode and you are ready to go.

Dave
 
The key is to have the specailly made prop socket. MarineMax sells them for $65 if I recall. They are also available on ebay from time to time. Do NOT try any other kind of wrench, strap or socket. Also, pnuematic air gun won't work with the socket - you'll need a long HD torque wrench or breaker wrench to attach to the socket. Use only wood (2x4 or 2x6) to brace the prop. Grease the shaft and seals, then put it back together. The prop-alignment thing will take you a minute to figure-out. I suggest using a permanent marker and draw a line from one prop to the other and then from the prop to the drive so that you know where you started.

Atlantis has a great following on prop reconditioning but I have not used them nor do I know someone who sent the BIII props there. I suspect it would not be inexpensive as there's alot of Stainless there for them to work on.
 
Are you just using the cavitation plate as a reference point? I don't see the significance of this. The props are counter rotating and blades will line up as they pass each other no mater how you put them on. It's my understanding that the props can be installed any way and timing isn't an issue, although way back in the early days of dual counter rotating props it was.
 
A lot of wasted space concerning this subject filling many threads on this and other boards, with so called experts from both sides of the discussion. Correct, the blades will obviously cross three times per rotation, so why would it matter where they cross? Speak to the guys at Mercruiser and they will tell you there is no such thing as "prop timing". The cavitation plate is used as a reference point by those who believe it makes a difference. I've tried it both ways on several boats and I can't tell the difference. People are going to believe what they want to believe.
 
Woody, next time you are in Oshkosh stop at Sweetwater marina. The owner is the retired engineer from Merc Cruiser that developed the BIII counter rotating system for Mercury (actually copied Volvo) and insists on the out of phase set. Just stop by and ask for the owner. He will talk your ear off.
 
Why wait? Just pick up the phone and call Mercruiser. They'll advise you and they wont talk your ear off.
 
Not crossing at the cavitation plate makes sense to me. Mine are currently set staggard at that point.

There was a thread on hear about that subject. put on with crossing at cavitation and there was a vibration, switched to staggard at cavitation plate and no vibration.

I was curious about removing the nuts, etc.
 
jg300da said:
Why wait? Just pick up the phone and call Mercruiser. They'll advise you and they wont talk your ear off.
Click to expand...
It doesn't make any sense to me. The props can never be out of phase with each other. So, I did call Mercruiser. They clearly said that it does not matter. Put the rear prop on any place you like and the same for the front.
 
Woody said:
It doesn't make any sense to me. The props can never be out of phase with each other. So, I did call Mercruiser. They clearly said that it does not matter. Put the rear prop on any place you like and the same for the front.
Click to expand...
Sorry but they're wrong.
True, the props turn at the same speed in opposite directions (if that's what you mean by 'phase') but if you're looking down the prop shaft, the blades cross each other in 3 spots on the 360 degree rotation. Make sure they don't cross under the cavitation plate.
I didn't believe it either so I did the test. I put them both straight up for the first test and yes, there was a noticeable vibration. So I took the rear prop off, rotated the front one so a blade was straight up and then slid the rear one back on with the blades are at 60, 180 and 300 degrees so they don't cross at the cavitation plate and guess what? The vibration disappeared.
One of my best buddies is a licensed Merc. mechanic and he said that 'timing the props' is common knowledge amongst the mechanics but oddly enough it's not written in any manuals.
Time your props.
 
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Hmmmm.....how is something that is "common knowledge" amongst "mechanics" debunked by Mercruiser themselves? On multiple occassions?
Anyway, goes back to what I stated earlier, people who want to believe it are going to find a reason to believe it. Whatever works for you.
 
Guys..........look at it this way. It takes no more time to put the outer prop on in the "clover leaf" position than it does to just slap the outer prop on without regard to positioning it properly. As such my suggestion is to mount them in the way I mentioned.

I had a vibration on my Bravo 3 on my previous 240 Sundeck when the props were not mounted properly. Remounting the outer prop made it go away. Others report no difference regardless of how it's mounted so there will always be some controversy here. I can also tell you that all the Technicians at our dealership mount Bravo 3 props the way I described.

Dave
 
I have an idea......Why not mark the props with a permanant marker on either the port or starboard side and put them back on with the lines connecting.
That will put an wondering or superstition to rest. I rest easy when I am confident I put things back together correctly, or at least I think I did!
 
What's missing from the discussion is that for some reason it seems to depend on the boat to which the B III is installed.
I did call Mercury, and their official word is that it doesn't make any difference how the props are installed with each other.
I will also tell you that it does make a difference on a Searay 240 DA.
Bottom line is if you have vibration, or cavitation issues in a turn, install your props as outlined by Dave S. and your problems will go away.

Cheers,

Jim
 
Weave said:
I have an idea......Why not mark the props with a permanant marker on either the port or starboard side and put them back on with the lines connecting.
That will put an wondering or superstition to rest. I rest easy when I am confident I put things back together correctly, or at least I think I did!
Click to expand...

Good concept unless they were installed right or wrong in the first place:smt021. That wont work for me anyway because I'm taking mine off and giving them to one of my firefighters for him to powder coat in an effort to reduce electrolosys (SP?)
 
dpvandy01 said:
Good concept unless they were installed right or wrong in the first place:smt021. That wont work for me anyway because I'm taking mine off and giving them to one of my firefighters for him to powder coat in an effort to reduce electrolosys (SP?)
Click to expand...

I would caution you to not powder coat them. I don't think with powder coating you can regulate the amount of material adhered to the surface and it may cause a vibration.

Stay up on your zincs and find out if anyone has powder coated their props will success first.
 
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