Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 13-05-2015, 13:09   #1
Registered User

Join Date: Apr 2015
Location: St Augustine, Fl
Boat: Endeavour 42
Posts: 23
New prop question / Maybe nuking things out

I recently sent my 2 bladed 63mm Max-prop in to get refurbished. PYI recommended buy a new (refurb) from them, because refurbing mine would be about $200 more than the cost of the purchased refurb... Either way , it's several hundred dollars more than I'd like to spend. Cost projection was $300-400, not a boat unit +.
This is where it gets to the nuking part. The Westerbeke manual ( I have a 44b in my boat) gives recommendations based on reduction ratio and ERPM. I have a newage PRM 120 pushing a Walter V-drive which spins the shaft. Both units have a 2:1 R/R. Shouldn't the overall R/R of the system be 4:1? Multistage reduction systems you multiply the ratios of each stage...
And I obviously need to determine cost / value ration for buying a refurb vs a new more affordable prop
__________________

__________________
AnnOMalleys is offline   Reply With Quote
Old 13-05-2015, 13:14   #2
Moderator Emeritus
 
David M's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: San Francisco Bay
Boat: research vessel
Posts: 10,150
Re: New prop question / Maybe nuking things out

Are you asking which size you need?
__________________

__________________
David

Life begins where land ends.
David M is offline   Reply With Quote
Old 13-05-2015, 13:33   #3
Registered User

Join Date: Apr 2015
Location: St Augustine, Fl
Boat: Endeavour 42
Posts: 23
Re: New prop question / Maybe nuking things out

Actually a two part question -
1) What's the reduction ratio I use to select a prop?
2) Just about every discussion I've read has said Maxi-Props are darned good props. I'm not racing, I'm coastal, maybe some water sailing">blue water sailing in a year or two. Is it worth a 400-700 dollar difference? Go with a good 2 or three bladed fixed instead, and save a bunch of dough...
__________________
AnnOMalleys is offline   Reply With Quote
Old 13-05-2015, 14:39   #4
Registered User
 
UNCIVILIZED's Avatar

Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
Re: New prop question / Maybe nuking things out

You'll likely both drive yourself mad, trying to figure out exactly what size, & pitch prop to get, based on the info which you're currently working with.
Yes, there's a science to picking a prop, or rather, getting close anyway. But much of it's based on data compiled over time. Factoring in; hull shapes, engine & transmission gearing, boat weight, underbody profiles, windage, engine torque curves, etc. etc.

If you get a Max-Prop, the pitch is adjustable with it on the boat, with the boat in the water.
Plus they give a superb amount of thrust in both forward AND reverse. Not to mention next to no drag when sailing. Oh, and they ain't half bad when it comes to fuel consumption either (sic).

Unless you're budget's super tight, snag one, or one of their competitors. There are a couple of other brands which also offer great efficiency in terms of power transmission, both in forward & reverse, that you'll run across on here if you do a bit of digging (or someone's kind enough to chime in about).

The bottom line (for me anyway) about them, is how much thrust which they can generate in only a couple of seconds, when shifting them from forward into reverse (and vice versa).
That confidence removes a lot of the sense of hairiness out of close quarters maneuvering.
__________________

The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
UNCIVILIZED is offline   Reply With Quote
Old 13-05-2015, 17:17   #5
Registered User

Join Date: May 2012
Location: Western Wisconsin
Boat: O’Day Daysailer II, 17'
Posts: 572
Re: New prop question / Maybe nuking things out

Your two reductions of 2:1 will result in a 4:1 reduction. Your propeller RPM is going to be lower than most boats. Is this a custom installation? If so go buy Propeller Handbook by Dave Gerr if you want to go with a cheaper fixed blade. You say this is a 63mm propeller which is probably really a 63cm so that is a diameter of about 25 inches. What happened with the old propeller? Is the material all eroded from cavitation because a high pitch was needed to get the engine RPM down to a reasonable value? I am thinking your propeller diameter is too small for such a slow turning propeller. However, a slow turning propeller is less likely to have a cavitation problem. Talk to you propeller manufacturer and tell them what your horsepower is going to the propeller and what the maximum engine RPM is with the 4:1 reduction. Also tell them how much clearance there is between the propeller tips and the bottom of the boat. Do not measure straight down from hull to propeller tip. Instead, move the ruler back and forth from tip to hull to find the least distance possible. I am thinking you will need a bigger propeller, either a larger diameter, or more blades.
__________________
westwinds is offline   Reply With Quote
Old 14-05-2015, 16:55   #6
Registered User
 
Capt Gary's Avatar

Join Date: Jan 2013
Location: CT
Boat: Pearson 39-2
Posts: 59
Re: New prop question / Maybe nuking things out

Seems like you are getting a pretty high estimate for refurbishing your 2 bladed prop. I had my 18x14 repitched to 18x16 and refurbished/rebalanced at Hale propeller in Old Saybrook, CT for about $200. They did an awesome job!
__________________
Capt Gary is offline   Reply With Quote
Old 14-05-2015, 21:17   #7
Registered User

Join Date: Apr 2015
Location: St Augustine, Fl
Boat: Endeavour 42
Posts: 23
Re: New prop question / Maybe nuking things out

Capt Gary - PYI quoted me - caveated of course because they hadn't seen the prop- an average prop refurb from them is in the $400 range. Thats what I was sort of figuring on. But, my prop has been sitting in saltwater for over two years with no cathodic protection at all, and I don't know when it was serviced before that. It could be original for all I know
__________________
AnnOMalleys is offline   Reply With Quote
Old 16-05-2015, 09:32   #8
Registered User

Join Date: Sep 2014
Location: Tracys Landing, MD
Boat: TPI, Manta Clipper, 34' DeFever CPMY 49
Posts: 24
Re: New prop question / Maybe nuking things out

You guys are all missing it, contact PYI again and ask them for recommendations. Stay with the max prop, go to a 3or4blade for superior smoothness and max thrust. If you don't get it right the first time, you can always change it at haul out for no charge. Water proof grease will last a season, don't forget to use the grease fitting that comes with the prop, regular fittings don't work well.
The props work great, used to sell them, have one on my boat.
__________________

__________________
Captain Bill 3 is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
A Headgear question, maybe one for those from Oz?? David_Old_Jersey Auxiliary Equipment & Dinghy 31 14-05-2008 21:20
Trying to figure out some things rscottm Meets & Greets 11 10-01-2008 13:06
Things that work and things that don't... svHyLyte Construction, Maintenance & Refit 58 03-11-2006 23:13
Dumb Question maybe kcrompton General Sailing Forum 4 29-12-2004 13:52
Maybe, Maybe Not Troubledour Health, Safety & Related Gear 0 25-09-2003 02:09



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 13:13.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.