Max Prop Issues -cavitation and poor performance

[Emouchet]

I think also it is a pitch issue. It took me 3 (!) visit in the slings for a short haul out to set the pitch correctly on my 2 blades max-prop. I have an old type, that cannot be adjusted easily under water.
Now, it works like a charm, forward and backward.

My boat is 18000 lbs, 39', running of a 3 cylinders Volvo 2030, and I can reach about 7.00kn on a calm day at 3100 max rpm.

[Alita49DS]

"Max-Props are easily adjusted underwater."

Really? Best of luck then. Here is a link to the instructions for mine.

https://1drv.ms/b/s!AqLwtI1czSAlgnHj9Z1HW4ZZ96FF

I am not sure that I can understand the instructions on dry land. Let alone try to put then into effect under water.

I suppose that at least one would not hear the bits dropping to the bottom.

[Jammer]

Well, the sticky wicket there is getting the hub filled with grease while underwater.


The new ones have little allen head adjustment screws that are accessible from the outside of the propeller.

[billknny]

Originally Posted by Halien

Max-Props are easily adjusted underwater. In my case, the choices were either to get in the water myself, haul the boat just for the task, pay our regular diver to do it, or wait for the next scheduled haulout. I considered doing it myself, but octopuses, crabs, jellyfish, and curious harbor seals freak me out, so I had our regular diver do it. It cost about $100 on top of our regular bottom cleaning. I'm sure it took him about five minutes, but he's a nice kid trying to make a go of it, so it was a win-win. The least expensive option for me was a minor windfall for him.

There are a several different flavors of MaxProp.

The "Classic" model is most certainly NOT "easily" adusted underwater, and you should not expect a diver to be able to do it unless he has done it before. It must be fully disassembled and put back together. It is a three hand job on dry land. I know of one diver (there are more I am sure) who can do it, and he has my utmost respect and admiration.

The newer, more expenive, "Easy" model is adjustable from underwater without a great deal of difficulty.

[billknny]

Originally Posted by Jammer

Well, the sticky wicket there is getting the hub filled with grease while underwater.

Actually, that is the easy part. You install the zerk fitttings it comes with, and use a grease gun to pump it full.

If you had to assemble it full of grease while underwater... geez... that is tough enough on land...

[wannacat]

Oregonian is definitely right about mixing up the left and right blades! Also, my Max Prop came with the blades marked incorrectly from the factory so that I indeed did assemble it backwards until we figured it out!!! The 1 dot and 2 dots were reversed, we had a ton of cavitation that way!!! We re-installed it [also remarked each blade for future] properly and it's been great now for over 20 years! I love it! As far as greasing it, that will only affect it's ability to feather when under sail, as it's gear driven and will definitely be at the pitch that it's set for when motoring. Contact PYI as mentioned by others, they will sort it out for you.

[Nicholson58]

Originally Posted by StuM

When was the last time it was re-greased? It should be done annually.

Grease per mfg instructions. Also check bushings and pins clearance. This should be a nice close fit without wobble. I have seen these with excessive clearance.

Pitch could be too aggressive. Check their technical assistance.

[Olly75]

Originally Posted by Alita49DS

What is the email address for whoever PYI are please?

Last time, a few years ago, when I wrote to whoever about the setting for my three bladed MaxProp I had a very pleasant conversation which got me precisely nowhere. The suggestion to try different settings seemed to overlook the fact that the prop was underwater and lifting a 49' boat is wallet damaging.

BTW, one thing that I can pass on about MaxProp is to only buy the genuine anode. It has a steel plate in it. The cheaper copies fall off in no time leaving just the set bolts. That is because the lugs erode away first.

Just phone them up, and they will give you the pitch there and then. Did it last week and they were very helpful.

[japarker11]

E-man,

You bought a 35 yo classic, but are being bitten by previous owners progressive decision making. They often start with flawed objective and after a couple of owners attempts to modify you end up with your situation.

Start over again cranking the numbers, engine hp/rpm fuel burn curves, gear reduction ratios (forward and reverse), prop rotation, down angle of the shaft log/shaft and clearances of the existing prop blades to the hull and rudder/skeg.

Let pyi, flex fold, Gori..... make their recommendations. My guess, the 17"x2 blade will not cut it.

No fear, your two blade Maxi has EBay power. It will still be scary for the next one. In the meantime, find a 17"x? three blade fixed In a pawn shop. An experienced diver can get the Maxiprop off without losing too many bits. Be mindful that the prop shaft threaded section has been hacked and will need a locking mechanism as the hole for the cotterpin is gone.

The Yanmar 4jh4 has too much to offer in terms of power and fuel economy to have it doing scrambled eggs. And life is too short not to be sailing.

Cal 39-2 are great boats, capable of around 6.5 knots cruise at 1.2 gph.

This experience comes from a 19"x22 deg x 3 blade Max prop driven by a 4jh3-te. During a three year haulout we reverse engineered the v-drive, dripless seal and max prop. The only thing we changed was painting the prop. After 20 hours, it seems the teflon allows the engine to speed up to the max hp rpm which it could not do previously. With our down angle, prop walk and astern power it spins in nearly its own length. Cruises at 2600 rpm, 7.4 kn 1.33 gph.





John P
S/V Odyssey

[japarker11]

I can't resist.

I forgot to add:

"ALL IS NOT LOST". In my response.


John P
S/V Odyssey

[StuM]

Originally Posted by billknny

you should not expect a diver to be able to do it unless he has done it before.

I'm having a bit of difficulty with that logic

[Pauls]

In addition to the previous posts about correct assembly and lube, there is a very basic point. A propeller - any propeller - must have enough blade area for the power being put into it. Insufficient area equals cavitation. Period. So check the blade area required for your boat. You can find references on how to do this yourself in Dave Gerr's books, or have a company that specializes in props calculate it for you.

Many sailboats have props with marginal blade area.

[epoxyman]

Well Folks, as expected you have given me some very thoughtful input based on a broad spectrum of knowledge.
The MaxProp I have (attached) I believe is an older classic model.
The previous owner said that typically it is greased every year however it was not done this year (a comment about the allen screws potentially going too far in) seemed to not get a lot of thrust from the moment she splashed.
No problem getting to the 2800-3000 rpm but I did not want to run continuously over 2600 rpm (last boat - Whitby 42 had a Ford Lehman that ran at 1500 rpm and above 2600 just made me nervous). What I found was the Yanmar 4JH4E ran beautifully this season (110 hours and counting) but that the MaxProp 2 blade was making more noise at low rpm unless I put it in reverse hard and than back to forward. From the input I believe I may be fighting at least 2 issues: 1- not greased and therefore rough engagement, and 2- possibly an undersized or improperly pitched two blade Classic MaxProp (17 inch diameter and 16 degree pitch).
Flexofold recommended a: 3-blade 18x14-3R Flexofold with hub for ISO / SAE standard shaft.
The sailing season is over in a month in Maine so I will address this at haulout. I will also contact PYY to get their input and find out the price to recondition. The new Flexofold is about $2 boat bucks.
I had a Flexofold on a saildrive Yanmar on a Pearson 365 and it was wonderful. I was just trying to get a sense if the 2 blade Classic Max prop was a better paperweight Vs. a prop.
Thanks again

[Terra Nova]

The previous owner should have installed the 3-blade MaxProp.

[epoxyman]

Well Folks, as expected you have given me some very thoughtful input based on a broad spectrum of knowledge.
The MaxProp I have (attached) I believe is an older classic model.
The previous owner said that typically it is greased every year however it was not done this year (a comment about the allen screws potentially going too far in) seemed to not get a lot of thrust from the moment she splashed.
No problem getting to the 2800-3000 rpm but I did not want to run continuously over 2600 rpm (last boat - Whitby 42 had a Ford Lehman that ran at 1500 rpm and above 2600 just made me nervous). What I found was the Yanmar 4JH4E ran beautifully this season (110 hours and counting) but that the MaxProp 2 blade was making more noise at low rpm unless I put it in reverse hard and than back to forward. From the input I believe I may be fighting at least 2 issues: 1- not greased and therefore rough engagement, and 2- possibly an undersized or improperly pitched two blade Classic MaxProp (17 inch diameter and 16 degree pitch).
Flexofold recommended a: 3-blade 18x14-3R Flexofold with hub for ISO / SAE standard shaft.
The sailing season is over in a month in Maine so I will address this at haulout. I will also contact PYY to get their input and find out the price to recondition. The new Flexofold is about $2 boat bucks.
I had a Flexofold on a saildrive Yanmar on a Pearson 365 and it was wonderful. I was just trying to get a sense if the 2 blade Classic Max prop was a better paperweight Vs. a prop.
Thanks again