New propeller, 1993 Albin 28 TE

[tomcat rio]

I had an 18x26 four blade Nibral with a 2.00:1 transsion and a new 310 hp Peninsular.

I thought it was under proped, so i put a 19x26 on it.

I like to cruise at 10 gph....it makes the math easier when figuring nm/gal

Old numbers:
10 gph, 2900 rpm, 14.5-15.0 kts.

New numbers:
9 gph, 2800 rpm, 16-17.0kts.

Top end at 3600 rpm, 21 kts, fuel flow 15gph (i know, i know you guys with the rice burners do much better ).

I guess i can live with a 1.6 nm/gal cruise.

I'm not gonna save enough to pay for the new prop any time soon, but there is some satisfaction is getting a little more effiecient. Another advantage of the larger prop is a noticeable increase in 'steering torque' [prop walk] when docking.

The fluel flow numbers are based on a flowscan gage, not a computed average. The speed is from the gps.
It was somewhat choppy on the peconic bay, with 15 kts of wind out of the north.

[DougSea]

Tomcat,

Thanks for sharing the performance info. I don't have any real numbers on my boat yet but it's great to have some reference numbers from a similar boat.

I'm looking at having my prop professionaly tuned over the winter, can you give me a ball park as to the price you paid for your new one? Is it a 4 or 3 blade? I'd like to have something to comapre the cost of the tuning to.

Many thanks,

Doug

[jcollins]

Tomcat,
Are you carrying alot of weight? Your numbers for cruise are getting closer to mine but it seems top-end is not... I will document my RPM/Speed this week.
I could swear that I was running 3400/24.5 last week.
I cruise at 2800/17-18. Of course it could be that I don't have a pilot house.

[tomcat rio]

its a michighan wheel 4 blade cupped nibral is was just over $1.0 k...
i'm not sure about tuning costs.
...
as i posted, not a tremendous performance change, but noticeable.
...
i got this book from amazon.com
...

The Propeller Handbook: The Complete Reference for Choosing, Installing, and Understanding Boat Propellers by Dave Gerr (Paperback - Jun 11, 2001)
Books: See all 1004 items
Buy new: $19.95 $13.57 In Stock
Used & new from $9.65


somewhat esoteric, but i got quite a bit out of it and found out that most, if not all the guys who work on or sell boats know little or nothing about how a prop works.
...
get the book.
ed

[tomcat rio]

i'm not carrying a lot of weight but my boat is one of the first (1993) and for whatever reason (basic weight) it may not perform as well as newer ones.

[jcollins]

Tomcat,
Makes sense. By the way...which one are you in the photo you attached?

[tomcat rio]

..i'm on the right (1969)..this one is a little more recent (last month). no, image is not upside down.

i is.



http://static.flickr.com/11/95459788_e9593fb36c.jpg

[tomcat rio]

as posted, my pitch is 26 which seems high. most albins like mine seem to have 19x18 props..
i suspect that most reduction ratios are on the order of 1.57:1, at least with peninsular driven boats.
..
i opted for a 2.00 ratio based on the calculator over at boatdiesel.com.
..
as near as i can see, this ratio provides a greater pitch selection, which, when you get down to it is more a black art than a precise science...
..
also, the boat was hauled for the prop change this morning. and , truth be told, i did observe a few more layers of bottom paint aboard than probably need to be there...soooo.

[DougSea]

Ah yes, bottom paint...

Part of my interest in your prop sizing comes from my frustration with mine. On the maiden voyage with my boat this past July I hit a piece of floating lumber in Long Island Sound and damaged my prop (and shaft!). I had it reconditioned, which got rid of the vibration, but I lost 200 rpms or so, down to between 32-3300rpm. Figured they put too much 'cup' in the prop when they re-did it so I'm going to take it to a prop-analysis outfit after she's hauled.

In the meantime though my RPMs have been dropping off more and more...freaking me out a bit. Changed my fuel filters this past weekend (different post) and ran back out to test out my re-found power. Nothing, Nada...

Said to myself "there's something wrong here" so I put on the bathing suit and over I went into the lovely cool waters of the sound.

I have an aquatic garden growing on my hull. The layer upon layer of old bottom paint, the ONE thing the surveyor picked on in my survey, is worthless. Not only am I getting the surface drag of the crummy paint, it's not killing anything! Spent an hour scraping as best I could and managed to pick up about 150 rpm. I'm thinking seriously of having the bottom 'soda-blasted' over the winter and putting on a nice fresh coat of high performance paint for next year.

And it took me two hours to warm up after my dip!

I love the Albin but it's going to take me a while to get used to a boat that I can't haul out whenever I want and I can't swap out props like on the old outboard.

I did find a local dive service that I'm hoping can clean the bottom for me relativly cheaply.

Doug

[DougSea]

BTW - Cool picture. So is 'rio' Radar Intercept Officer'?

[JackK]

I had my prop scanned at Ocean Props (Middletown, RI) this spring.
If the report would be of any help as a reference to bring yours back to spec, send me a msg and I will forward it. Mine is a 19 x 19 4 blade.

BTW - I would reccomend Ocean Props. My prop scanned at a Class I so no real work was required. He balanced and cleaned up a couple of small nicks in the prop for next to nothing.

Jack

[tomcat rio]

...i read that even brand new props should be scanned. apparently, tolerances are quite wide in the manufacturing processs.

[DAVEWAXX]

I heard they make a 5 blade prop for better performaance any one hear of this??

[Denis]

This startled me, I thought TOMCAT was back.

[jcollins]

Yeah...me too. Denis - check the other post about temperatures.

thanks,