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Old 14-02-2011, 08:24   #1
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Rebuild Max Prop - Ouch !

Below is an email from PYI covering the rebuild of my Max Prop. I knew it was time as the blades were wobbly. These guys are very professional and were very promt in their response time. I was hoping it would not be so bad but I guess its still about 1/2 the cost of replacement. The rebuilt one should last longer as the PO was pretty rough on this boat...




This message is a written estimate regarding the repairs of the Max-Prop Classic sent to PYI INC. The following is a description of the repairs, and estimates:

Based on the condition of the prop there are two estimates each containing different issues we can fix. I evaluated the prop and this prop is in bad shape and will take an extensive amount of work to restore. First off the prop has a significant amount of pitting cavitations on the blade surfaces, this has contributed to chipping on the edges, and the blades to wear thin throwing the prop way out of balance, a major resheeting is recommended to restore the blades. There is also a major amount of fore, aft, and rotational play in the blades exceeding factory standards. The specific cause for the fore and aft play is a result of the spacer wearing. The central cone gear is worn opening up teeth allowing the cone gear to fit in a loose fashion in the blade teeth, this is rotational play. A new central cone gear will clean up this play. The bearing surfaces in the spinner halves have worn enough for the central hub to become loose as well, a new replacement hub will tighten this up and significantly reduce any vibrations the boat may have been experiencing. I suspect that with all of this damage that the prop is causing a lot of vibrations throughout the boat, and will need to be addressed so that these vibrations don't cause any harm to the engine or other parts of the boat.

The first estimate consists of a basic recondition. A balance, and tightening that requires a new spacer to clean up the fore and aft play, a new cone gear to clean up the rotational play, and a new hub to fit taught in the spinners, this will clear up all the play in the blades and spinners. This also includes a spot weld, where we spot weld any major pits or cavitations to properly balance the prop. Keeping in mind the blades will still have cavitations on them and may lead to future problems. The last step we do is polish the prop to get it looking close to new again. The cost of all the work listed above in estimate one is: $1,225.50

The second estimate includes all the work listed above in estimate one, plus a full re-sheet of the blades. We will balance, tighten, polish, and resheet (rather than spot weld). A re-sheet job means we'll re-weld new material across the surfaces of the blades filling in all pits, and cavitations created from electrolysis, and restoring the blades back to proper shape and thickness. We use the same material the prop is made from and will not reduce or threaten the integrity of the blades. The work done in the second option will bring the prop back to 95-98% like new and costs $1,775.80.

To compare the repair costs to the cost of a new prop of the same specifications the retail value is: 21" diameter, 70mm three blade Classic is $3,400.00

If you have any questions, concerns or would like to proceed with the repairs please feel free to contact me.

Thank you,
Best regards,


Danny Mullen
PYI Inc.
p. 425-355-3669
f. 425-355-3661
mpservice@pyiinc.com
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Old 14-02-2011, 08:41   #2
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Sounds like the prop went unprotected by a zinc for an extended time.
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Old 14-02-2011, 08:47   #3
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Hard to say as I only recently aquired the boat and it was supposedly serviced annually by none other than Hinckley Yachts in Portsmouth RI... Actually the prop did not appear to be suffering from electrolosis as there was not any pink coloring but the pitting im sure was a sign of what was to come. I suspect the prop was never greased as when I took it apart there was not a lot of grease and what was in there was old. Again though I will never know what was done in the past and Can only look forward to a better maintennance schedule. Funny thing was the lack of vibration, I actually thought the boat motored pretty smoothly. Guessing it will be even better with the rebuild!
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Old 14-02-2011, 08:52   #4
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Originally Posted by SV Escape Plan View Post
Below is an email from PYI covering the rebuild of my Max Prop. ...
Thanks for posting that. This topic and that email are very interesting to me as I was considering a Max Prop for my boat.

A few questions, if you have the time, or if they even apply...

Did you buy the prop new?

Did you consider any other brand(s) as a close second best?

How many hours did it take to wear it like this?

Are you satisfied overall with the prop, its performance and its advantages - if it were damaged beyond repair, would you buy another knowing what you know now?

Anything you could say about it would be of interest.
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Old 14-02-2011, 09:00   #5
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To answer your questions:

1. I did not buy the prop new. I bought the boat last spring. No idea what the actual maintennance schedule was.

2. I have used Maxprops on all my boats and am a big fan but if I was starting from scratch today I might consider some alternatives. I stick with Maxprop mainly because their service and support is top notch, they have been making feathering props longer than anyone else (I think), and zincs and other parts are available easily pretty much anyplace.

3. The engine has about 2500 hours on it but I dont know if this prop came from the factory on the boat in 1984.

4. I am satisified with the prop and will get it rebuilt as the rebuild is roughly half the price of a new one and given the abuse this prop has seen I am impressed. I suspect the main culprit to its wear was the lack of greasing. This must be done annually and many people simply dont bother. I also suspect that the zincs may have been replaced but not with the propper level of cleaning to ensure a low resistance connection.

There are certainly other choices in the feathering prop universe and probably better props than the Maxprop but when I put all of the considerations together this prop still makes the most sense for me. As always Your Mileage May Vary, YMMV.
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Old 14-02-2011, 09:07   #6
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Originally Posted by SV Escape Plan View Post
I suspect the main culprit to its wear was the lack of greasing. This must be done annually and many people simply dont bother.
Actually, the literature for Max Prop recommends lubrication every two years.
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Old 14-02-2011, 09:07   #7
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A further reply to my question regarding source of wear and also pitch recommendations. Interesting that I nver told them what the prop was pitched at and the suggested 20*, other Amphitrite owners have suggested 21* to be ideal so this confirms their observations and furthers my confidence in PYI. As I mentioned earlier I continiue to be impressed with their support and quick response times.



Hello Ted,

There are many reasons of which this damage could be caused, and not knowing the history of the prop, it can be hard to pin point the exact causes. As far as the play goes not properly greasing the prop will definitely wear the gears and bearing surfaces really fast, also hitting objects with the prop can wear/chip/break the teeth and blades away as well. If the prop is old, over time from normal use the gear/teeth can wear creating play as well. The pitting cavitations are caused from electrolysis. This damage can happen multiple ways as well, and the most common is not properly replacing zinc anodes when necessary. Depending on the type of water the boat resides in can effect the prop with electrolysis as well, for example warm water, ungrounded electrical currents, and motor boats in same marina can substantially increase electrolysis damage and eat the prop within days. In order to have a prop last to its full potential, keep it properly greased and replace the grease yearly. Keep up on the zinc anodes double check to see when the zinc is about its end and replace when needed. When motoring properly feather the prop from forward to reverse by shifting into neutral first, to allow the prop to feather smoothly from gear to gear, rather than throwing the boat from forward to reverse to stop fast causing the prop to slam from gear to gear. This will also prolong the life of the transmission and engine too. In regards to your question of a proper pitch based off the information provided the recommended pitch is 20* degrees. When we get an agreement with the estimate, then we begin the repairs, when the prop is done and ready to be shipped back we'll contact you for payment and shipping information. If you have any other questions or concerns feel free to ask.

Thank you,
Best regards,


Danny Mullen
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Old 15-02-2011, 07:40   #8
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I had Max-prop rebuild my prop a few years ago, and the cost came in about half of a new propellor. It had 5500 hours on it and was getting a bit wobbly. I didn't notice any vibration under power, but did notice it when motorsailing.

The prop came back nice and polished, and looked like a new one. The vibration when motorsailing was gone.
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Old 15-02-2011, 10:37   #9
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I had Max-prop rebuild my prop a few years ago, and the cost came in about half of a new propellor. It had 5500 hours on it and was getting a bit wobbly. I didn't notice any vibration under power, but did notice it when motorsailing.

The prop came back nice and polished, and looked like a new one. The vibration when motorsailing was gone.
Thanks for the data. Did you lube it during that time? How often? I dive to do my own bottom work as needed and considering the cost, might be down there lubing that thing twice as often as they recommend.

5500 hours seems pretty reasonable, although when I think of it, that comes to almost 60 cents per hour of motoring for the $3150 cost of a new Maxprop for my boat...

And if my Westerbeke 4-107 will go, maybe, 10k hours before it needs an $8k rebuild, that's 80 cents per hour for engine rebuild costs. Considering it like that, the Maxprop starts to sound pretty expensive... 75% as expensive as the engine itself for rebuild costs...

Is this a realistic way to look at the costs when weighing the advantages?
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Old 15-02-2011, 18:38   #10
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5500 hours seems pretty reasonable, although when I think of it, that comes to almost 60 cents per hour of motoring for the $3150 cost of a new Maxprop for my boat...
Your logic is flawed, IMHO. You reap the benefits of a Max Prop every second the boat is underway, whether motoring or sailing.
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Old 15-02-2011, 19:17   #11
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Originally Posted by Whimsy View Post
Thanks for the data. Did you lube it during that time? How often? I dive to do my own bottom work as needed and considering the cost, might be down there lubing that thing twice as often as they recommend.

5500 hours seems pretty reasonable, although when I think of it, that comes to almost 60 cents per hour of motoring for the $3150 cost of a new Maxprop for my boat...

And if my Westerbeke 4-107 will go, maybe, 10k hours before it needs an $8k rebuild, that's 80 cents per hour for engine rebuild costs. Considering it like that, the Maxprop starts to sound pretty expensive... 75% as expensive as the engine itself for rebuild costs...

Is this a realistic way to look at the costs when weighing the advantages?
In my opinion that is a sound approach.

Every bit of gear on the boat has a useful life, and 5500 hours for a feathering prop sounds reasonable to me.

A good feathering prop is not a cheap item of equipment. Yes, the cost per hour of basic amortization is going to be even close to the engine (although the running costs are going to be of course much less).

Worth every penny IMHO.

I use a Bruton Autoprop which will be cheaper to keep going since it has no gears. If you can avoid frying the blades with electrolysis (and I've aready had my first brush), and don't hit anything with them, they will last longer, since the only thing you would ever need to replace are the relatively cheap bearings.

We had one on our old boat which is still going strong with over 10,000 hours on it, with nothing more done to it than scrupulous anode changes and an annual grease job.

But it hardly makes much difference. A good feathering prop, like a Maxprop, is one of those things so important to the boat's performance -- just pay whatever it takes and get on with it, I say.
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Old 16-02-2011, 06:55   #12
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Your logic is flawed, IMHO. You reap the benefits of a Max Prop every second the boat is underway, whether motoring or sailing.
That's a good point that makes sense to me. Thanks.

Wondering if anyone has done any realistic analysis of the drag of a locked standard prop, up to usual sailing speeds, and how much effect does that drag have on overall speed and pointing ability of a reletively low-tech hull shape like my Morgan OI 41?
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Old 16-02-2011, 07:06   #13
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In my opinion that is a sound approach.

Every bit of gear on the boat has a useful life, and 5500 hours for a feathering prop sounds reasonable to me.

A good feathering prop is not a cheap item of equipment. Yes, the cost per hour of basic amortization is going to be even close to the engine (although the running costs are going to be of course much less).

Worth every penny IMHO.

I use a Bruton Autoprop which will be cheaper to keep going since it has no gears. If you can avoid frying the blades with electrolysis (and I've aready had my first brush), and don't hit anything with them, they will last longer, since the only thing you would ever need to replace are the relatively cheap bearings.

We had one on our old boat which is still going strong with over 10,000 hours on it, with nothing more done to it than scrupulous anode changes and an annual grease job.

But it hardly makes much difference. A good feathering prop, like a Maxprop, is one of those things so important to the boat's performance -- just pay whatever it takes and get on with it, I say.
Excellent points. Thanks much!

I may prioritize an autopilot, newer genny and other "$2k+" items first, but the prop is on the list and will likely make it to the top, eventually.
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Old 25-02-2011, 18:04   #14
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Re: Rebuild Max Prop - Ouch !

I feel your pain. I just got my rebuild quote for a 17" 3 blade classic with maybe 1000 hrs on it: $1200. Interestingly, the assessment of my prop was almost identical to yours - verbatim. I never noticed a bit of electrolysis or "blade thinning" but there was certainly play in the blades.

I wonder if anyone has gotten off for less than a boat unit?

Knowing how much the thing cost, I was meticulous for the 500 hours I've owned it: grease every year, always properly "zinced" (or is it "zinked"?). Some years I lovingly applied Propspeed. I doubt the PO was as anal as I but I still was surprised how quickly it went sour.

Anyway, I am in no position to argue - just be a good boater and get out the checkbook...
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Old 25-02-2011, 18:42   #15
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Re: Rebuild Max Prop - Ouch !

I'm also a Max Prop loyalist and am wondering how your experience with the prop speed went. Any tips on the application?
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