The right prop

Report the performance of your boat, supply as much information as possible (weight, HP, prop, speed, etc.).
Subject: Make the Glen-L design name the subject. If the design already has a posting, add your information to that post.

Moderator: Bill Edmundson

Post Reply
fergal butler
Posts: 1292
Joined: Sun Sep 06, 2009 2:55 am
Location: Co.Dublin, Ireland.

The right prop

Post by fergal butler » Wed Nov 18, 2009 8:31 am

Hi I have a 50hp blueband on my malahini and would just like to know what size and pitch prop to put on it.this is the one that's on it at the moment :lol: :lol: THANKS. http://i753.photobucket.com/albums/xx17 ... ne/004.jpg

jcallends
Posts: 361
Joined: Tue May 26, 2009 4:46 am
Location: Coldwater Michigan

Re: The right prop

Post by jcallends » Thu Nov 19, 2009 6:25 am

Prop size is determined by boat weight, horsepower, and anticipated speed. Somewhere in my junk I have a chart for this published in a Mercury manual. If and when I find the manual I will post a copy of this chart.

upspirate

Re: The right prop

Post by upspirate » Thu Nov 19, 2009 6:37 am

I'm not sure how the ring around the prop affects the performance.

Is that ring-type prop required in your area?

Find out what RPM, pitch and diameter you are running now, and use that as your baseline.

If you are running lightly loaded,you should be at the top of your motors recommended RPM range.

If heavy,at the bottom of the range.

Best to prop it at medium to top of the range with the normal load you will be carrying(people,gear,towing tubes,skiers etc)

fergal butler
Posts: 1292
Joined: Sun Sep 06, 2009 2:55 am
Location: Co.Dublin, Ireland.

Re: The right prop

Post by fergal butler » Thu Nov 19, 2009 11:34 am

That prop was on the engine but I think it revs to high, there no numbers on it to get the size and pitch. The boat is about 500lbs and the engine a 50hp electric start No:3237433. I'am not sure if I can connect a tacho on this type engine or will it charge the bat,I have heard of a thing called a tiny tach that raps around a plug lead so I might get one if I cant connect my tocho that's in the dash,Thanks for your help.

upspirate

Re: The right prop

Post by upspirate » Thu Nov 19, 2009 12:32 pm

Have you taken the prop off?

Sometimes the part# and pitch is on the inside end.

Here's a link to Tiny Tach if you don't have it:

http://www.tinytach.com/tinytach/index.php

jcallends
Posts: 361
Joined: Tue May 26, 2009 4:46 am
Location: Coldwater Michigan

Re: The right prop

Post by jcallends » Mon Nov 30, 2009 7:01 am

Hi f b, I have found my prop charts and am attaching the one for 50 HP motors. There are 5 pages total and if I can figure out how to put 5 pages in one file I'll send all of them, Jack.
Attachments
Boat props 2.jpg

User avatar
Caber-Feidh
Posts: 828
Joined: Mon May 07, 2007 7:50 pm
Location: Battle Point, Leech Lake... tundrasota

Re: The right prop

Post by Caber-Feidh » Fri Dec 11, 2009 10:58 pm

To really get any idea you really do need some speed and rev counts. Even then getting the perfect prop is 1/3 luck, 1/3 science, and 1/3 just plain guessing. Hard to tell from a pix, but it looks shallow. Dump the ring unless somehow you find yourself stuck with it. Somewhere I remember reading they cost around 14% in efficiency - Don't quote me on that number, I can't remember where I saw it, but it would make perfect sense.

Borrow a GPS, and get some RPM readings. Both are of equal importance in getting a good match.
Some plan to stroll through Saint Peter's Gates, I plan to go through them at 150mph... backwards... in a screaming ball of flame, with a glimmer belt wrapped around my head, and a NOx button in my hand.

fergal butler
Posts: 1292
Joined: Sun Sep 06, 2009 2:55 am
Location: Co.Dublin, Ireland.

Re: The right prop

Post by fergal butler » Sat Dec 12, 2009 10:47 am

Thank's for that guy's also can I run a rev counter off the two wires coming from under the flywheel.Image

User avatar
Caber-Feidh
Posts: 828
Joined: Mon May 07, 2007 7:50 pm
Location: Battle Point, Leech Lake... tundrasota

Re: The right prop

Post by Caber-Feidh » Tue Dec 15, 2009 10:54 pm

If you are looking for a permenant install tach, I may have a diagram for that engine, need the serial, or the # off the control box to tell for sure. Mercury was a PITA in that vintage, you never knew what combination of random ignition components they were going to bodge together any particular day.

If it's the battery/CDI system, (most common with that flex-plate flywheel) you will find a medium brown wire (sorta the colour of chocolate ice cream) coming out of the CDI box. That is the tach-sense lead. Some CDI units have 2 browns, one will be jumped to a white, don't use that one, it's a cascade-trigger used when there are 2 ignition packs. The correct one will be all alone, not connected to anything.

The tiny-tach doesn't need all that work to hookup. If you are not looking for a nice, clean, cluster-mounted instrument, it's the way to go. Not the best looking items in the world though.
Some plan to stroll through Saint Peter's Gates, I plan to go through them at 150mph... backwards... in a screaming ball of flame, with a glimmer belt wrapped around my head, and a NOx button in my hand.

fergal butler
Posts: 1292
Joined: Sun Sep 06, 2009 2:55 am
Location: Co.Dublin, Ireland.

Re: The right prop

Post by fergal butler » Wed Dec 16, 2009 1:16 am

I have a rev counter in the dash just not wired up,The control box is new and just joined up to the old loom I don't have the old one, Thanks again.Image

Post Reply

Return to “Speed and Performance”