Reply
 
Thread Tools Search this Thread Display Modes
 
Old 07-01-2018, 08:44 AM   #1
Member
 
Join Date: Jul 2013
Posts: 6
Marine Trader 34: what propeller?

I have a MT 34 with a Ford Lehman 120hp and a Velvet drive. I feel like I have extra engine and could get a few more knots out of it. Currently at 1800RPM, I get 6knots. If I go to full throttle 2250rpm I only get 1 more knot. What propeller/pitch should I have on my Trawler?
__________________
Advertisement

edrnemt is offline   Reply With Quote
Old 07-01-2018, 10:35 AM   #2
Art
Guru
 
Art's Avatar
 
City: SF Bay Area
Country: USA
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 9,467
Quote:
Originally Posted by edrnemt View Post
I have a MT 34 with a Ford Lehman 120hp and a Velvet drive. I feel like I have extra engine and could get a few more knots out of it. Currently at 1800RPM, I get 6knots. If I go to full throttle 2250rpm I only get 1 more knot. What propeller/pitch should I have on my Trawler?
Welcome edrnemt!
__________________

Art is offline   Reply With Quote
Old 07-01-2018, 12:27 PM   #3
Senior Member
 
timb's Avatar
 
City: Oriental N.C.
Country: usa
Vessel Name: true heading
Vessel Model: marine trader 38 dc
Join Date: Sep 2017
Posts: 361
that's not much less than what mine does (135). is that when you also start making a wake? so first post in 5 years . welcome to posting. sounds about normal to me . but I'm kind of new .
timb is offline   Reply With Quote
Old 07-01-2018, 12:43 PM   #4
Guru
 
kapnd's Avatar
 
City: hawaii
Country: usa
Vessel Name: #31
Vessel Model: ex-Navy MUB 50 fish/cruise
Join Date: Aug 2013
Posts: 529
It’s a large, heavy boat with only 120 hp, so if you’re in a big hurry, you bought the wrong rig!
You might be able to optimize what you have with some careful data collection and the cooperation of a reputable prop shop.
Without LOTS more power, you must content yourself with a more leisurely pace.
__________________
You can lead a horse to water,
But you can't make him ski...
kapnd is offline   Reply With Quote
Old 07-01-2018, 03:01 PM   #5
Guru
 
djmarchand's Avatar
 
City: Litchfield, Ct/Punta Gorda, Fl
Country: USA
Vessel Model: Atlas Pompano 23
Join Date: Aug 2012
Posts: 4,650
Quote:
Originally Posted by edrnemt View Post
I have a MT 34 with a Ford Lehman 120hp and a Velvet drive. I feel like I have extra engine and could get a few more knots out of it. Currently at 1800RPM, I get 6knots. If I go to full throttle 2250rpm I only get 1 more knot. What propeller/pitch should I have on my Trawler?
First your prop is over pitched. The engine should rev to 2,500 at wot not 2,250. A good prop shop can rework your prop to remove 2" of pitch which should get you close to 2,500 rpm at wot.

But that will make your speed less at 1,800 not more, but it will be lots better for your engine. Running it as it is pitched now is like lugging an engine in fourth gear up a hill whereas shifting down to 3rd will let it speed up and run better.

6 kts at 1,800 with an over pitched prop sounds like too low a speed. Is your bottom clean and/or the prop?

With your prop repitched you could run the Lehman at 2,000 rpm but it gets pretty noisy above that. 2,000 rpm should push a MT 34 with a clean bottom to 7+ kts.

David
djmarchand is online now   Reply With Quote
Reply

Tags
mt34, prop pitch, propeller

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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





All times are GMT -5. The time now is 08:51 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012