Propeller reconditioning

[Noah]

Check you tachometer for accuracy before you make you decision to repitch based upon an assumed RPM of 3800.

[Breakin Away]

Check you tachometer for accuracy before you make you decision to repitch based upon an assumed RPM of 3800.

I checked it a few weeks after survey (and annually since). Spot on.

EDIT: To be clear, I've only tested up to about 2400 RPM, but everything is accurate and linear. I'm not sure I want to be around the motor when it's spinning at 3800 RPM.

[Stu Jackson]

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...or maybe it's time to think about a feathering/folding prop. Which brand do you guys like best? I want a design that also reverses effectively, since it's critical for dock maneuvering.

"Best" rarely works when talking about boats, which are inherently compromises, right?

I'd bet that if you typed "feathering+props" in the search bar you'd find lots and lots of comments.  Which, inherently, would be all over the place, for different and individual reasons.  There haven't been any new ones made in many years.

Good luck.

[Breakin Away]

I called Ray at Atlantis Propeller today and had a talk about my prop. Like Noah, he expressed some skepticism that my motor could have been actually revving at 3800 RPM, noting that the governor should prevent this. I'm so clueless about this stuff that I didn't even know that my engine has a governor, but after reviewing the service manual I know it has one, but I'm still pretty clueless about how it actually works. It seems it has to do something with springs interacting with the centrifugal force of the governor shaft to increase/decrease fuel flow if centrifugal force decreases/increases when load increases/decreases. But I digress.

I told him I'd do some homework and bring the prop by next week when I'm back home near Philly . In the meantime, I need to decide whether I should request any modifications to the prop. I assume that I have the standard 15"x9" three-blade prop (with pretty narrow blades) that Catalina supplied, and I'm sure he'll verify dimensions and pitch and tell me if it's something other than 15"x9". Since the boat is winterized on the hard, and I do not want to do multiple short hauls to seek perfection, I'd like to take the long-term view and get the prop little better for the coming season (i.e., RPMs closer to 3000), then verify top RPM after launch in the spring, then have him do a final prop adjustment (or replacement) while hauled out a year from now.

I'm always inclined to leave well enough alone, especially since Mainesail says too little pitch is better than too much. But knowing that I have the more powerful M35B engine, and reading here that there are people with M25XPBs who upped their pitch to 15"x10", I wonder if I shouldn't have him up the pitch on my prop to 10" (assuming, of course, that it hasn't already been increased). Then I'd check my max RPMs next spring, verify it with the strobe (since I haven't used the strobe above 2400 RPM), and do the final adjustment while on the hard in a year.

What do you guys think? Of those of you who have the MkII/M35B combination with 3-blade prop, what prop size and dimension do you have? Have you verified that it achieves a max RPM of 3000?

[Roc]

Roland,
I have found that not too many shops use Prop Scan.  There might not be any in Rhode Island.  You may need to ship it to whatever closest one you find.  That's what I did.  Shipping the prop is not that expensive.

[Breakin Away]

http://oceanpropsri.com/

New England's first prop repair shop with Prop Scan™

[Roland Gendreau]

Thanks for finding the Rhode Island prop shop Breakin.

I emailed them to confirm they had prop scan and got an estimate of $250 to $280 to recondition the prop.  The prop scan inspection is free.  It is interesting that all the testimonials they post on their web site are from large power boat owners.   

[Ron Hill]

Breaking : Re read my post which said that MANY people with the M25 XP engines (usually in the MK1 C34s 1987-1991s) upped their 3 bladed prop pitch from 9" to 10".
 
I did that I took my 3 bladed 15"X 9" to a local prop shop and asked them to repitch to 10". 
As I mentioned in my Mainsheet Tech note article, many years later (4-6? years) I took it to Black Dog Props (that used Prop Scan) to have them recheck my prop.  They found all 3 blades repitched differently!!!!!!  I had asked them for 10" and they told me that a couple of the blades were pitched to over 11" !!!!  They asked how the engine was doing and I said OK; so they suggested 11" on all blades so that's what I did.  That screwed up prop was on the boat when I went south for 9 months and I'll guess it had a couple of thousand hrs running time!!

So when I reengined to the newer M25XPB with 3 more HP the boat really took off!! Cruising @ 2300-2400 rpm.  So that's why I say with a 35 hp engine you should easily be able to handle 11" of pitch.

It's your boat so do what you want, but do NOT take your prop to a local prop shop - they will pull out a (well worn) 10" or 11" pitch block and then mallet your blades into submission. They do not have the capability to "calibrate" and/or "measure" each blade to make sure that each is "in spec" - from hub to tip!!

However,PLEASE just read the articles that are published and already out there!! 

A bunch of thoughts

[Breakin Away]

Thanks, Ron. That's EXACTLY the type of advice I'm looking for. I'll also check out your articles, but it sounds like my M35B should easily handle 15"x 11" without lugging the motor. I'll probably request this to start, and maybe request further tweaks next off-season.

Atlantis Prop is about the only shop within 40 minutes of my home. Their website also says they have prop scan. Are you aware of any reason not to use them instead of Black Dog?

http://atlantisprop.com/

[Ron Hill]

Breaking : It's the process "Prop Scan" that is important - measuring multiple zones of the prop.  I have no reason that Atlantis shouldn't use it as well as BlackDog does.   

My thought

[Breakin Away]

Breaking : It's the process "Prop Scan" that is important - measuring multiple zones of the prop.  I have no reason that Atlantis shouldn't use it as well as BlackDog does.   

My thought

Thanks, Ron. I found your 1991 Tech Note where you took it to your local shop, but having a hard time finding the article from several years later where you went to Black Dog. Do you have a link?

I'm also interested in hearing from anyone else with a M35B motor. What diameter/pitch do you have on your props? What is your maximum RPMs?

I'll be taking my prop to Atlantis sometime this week, so would like to know other owner experiences.

[Ron Hill]

Breaking : For the last time - if you have a prop larger than 15inches diameter, you are most apt to get hull buffeting!!

Your boat, your choice

A thought

[Bill Shreeves]

Atlantis uses Prop Scan and you'll walk away with the output of the scan for your reference.  I installed a new 3-blade sailor 15x10 on my boat two years ago and I'm very happy with it.  I typically cruise between 2,300 & 2,400 RPM.

[Breakin Away]

Breaking : For the last time - if you have a prop larger than 15inches diameter, you are most apt to get hull buffeting!!

Your boat, your choice

A thought

No repetition needed. I have no intention to buy a different diameter prop, and don't recall ever saying I would.

I just want to know what other people have on their boats so I can request an adjustment by Atlantis. They're very reluctant to increase pitch by more than 1" in one shot, so if PropScan says I have the factory default 15"x9" prop, I'm going to have to push him a little to increase it to 15"x11". If there's clear experience from multiple people that 15"x10" is still too little pitch for an M35B, it will help raise my confidence to push him to go to 11" pitch.

Last I checked, most prop shops don't have the technology to increase the diameter of someone's existing prop.    But if by some chance someone here has a smaller or larger diameter,  I want to know about it.

[Breakin Away]

I finally managed to get the right search terms on Google to bring up the correct Tech Notes. Since Roland has also had some problems finding the right articles, here's a quick chronological summary of documents that I found:

• Some discussion of propeller efficiencies: http://c34.org/mainsheet/pdf/1988_no3.pdf
• Upgrade to feathering prop: http://c34.org/mainsheet/pdf/1988_no4.pdf
• Use of 15"x10" 3B prop with M25, and recommendation for 15"x10.5" for M25XP: http://c34.org/mainsheet/pdf/1989_no1.pdf
• More on three-blade props and feathering props: http://c34.org/mainsheet/pdf/1989_no2.pdf
• Ron's first note on repitching to 15"x10" (which was later found to be 15"x11") with M25XP: http://c34.org/mainsheet/pdf/1991_no4.pdf
• Ron's second note where PropScan determined his prop to actually be 15"x11" and tweaked to more exact specs: http://c34.org/mainsheet/pdf/Aug-2001.pdf
• Feathering prop 2007: http://c34.org/mainsheet/doc/FeatheringPropAlternative.doc
• Feathering prop 2 2007: http://c34.org/mainsheet/doc/KiwiPropFollowUp.doc
• Mike Vaccaro's 2007 request for users' prop perfomance data for future Tech Note (which I could not find): http://c34.org/mainsheet/doc/PropDataRequest.doc
• Mike Vaccaro's request 2007 on message board, but responses exclusively dealt with folding props: http://c34.org/bbs/index.php/topic,3722.msg20674.html
• Ron's third note on using 15"x11" prop with M25XPB: http://c34.org/mainsheet/pdf/2010/Prop%20pitch.pdf

Everything I see suggests that 15"x11" (which ran well on both Ron's M25XP and M25XPB) would not overload any M35B. However, it's still a small data set, and most people who report data give their cruising RPM, not their maximum full-throttle RPM which is what Westerbeke uses as their guideline for correct prop pitch. So any other data from M35B owners would be helpful (especially if you've tested your maximum RPMs).

If Atlantis prop pushes back too hard, I might go to Black Dog, since it sounds like they've done this before with the Catalina-supplied Michigan Wheel 15" "Sailer" props. I expect that all these guys do 95% of their business with powerboats, so experience with our sailboats could be a differentiator.