Reply
 
Thread Tools Search this Thread Display Modes
 
Old 08-14-2017, 11:37 AM   #1
Senior Member
 
City: Madisonville
Vessel Name: Aku Uka
Vessel Model: 43’ DeFever
Join Date: Feb 2011
Posts: 213
Thruster Motor Change

Several people have told me I can decrease my thruster run time by going to a larger motor. There is a 6hp on it now and I can go up to an 8hp by simply swiping the motors. Everything else stays the same. Here's my confusion, if everything remains the same (prop, tube diameter, rpms) how will increasing the hp change anything? More hp should only come into play if the 6hp motor is being overloaded. What am I missing here. I don't mind the cost or labor involved but I'd like to hear from you guys before I make the plunge. Thanks.
Oh, it now takes about 45 sec. to make a 90 deg. turn in the harbor. I've been told it should be about half that.
__________________
41' Litton
Dixie Life is offline   Reply With Quote
Old 08-14-2017, 11:50 AM   #2
Guru
 
High Wire's Avatar
 
City: Cape May, NJ
Vessel Name: Irish Lady
Vessel Model: Monk 36
Join Date: Dec 2007
Posts: 4,966
The answer is "maybe". IF the lower unit can handle the extra power. IF the mounting is the same. IF the power cables were oversized with the old. IF the tunnel is big and deep enough. Get the point? Talk to the manufacturer.
__________________
Archie
Irish Lady
1984 Monk 36 Hull #46
Currently in Cape May, NJ
High Wire is offline   Reply With Quote
Old 08-14-2017, 12:13 PM   #3
Technical Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,194
More hp motor probably makes more rpm with same prop. Talk to mfr, often they use one gearbox and prop with different hp motors so the upgrade might be a no-brainer.

Before you do that, go put a voltmeter on motor terminals and have a helper run thruster. See what volts are there. If below about 10 (??) batt or cabling is not up to the job and that will have a BIG effect on performance.

Also, barnacles on the prop will kill performance.
Ski in NC is offline   Reply With Quote
Old 08-14-2017, 12:48 PM   #4
Valued Technical Contributor
 
DavidM's Avatar
 
City: Litchfield, Ct
Join Date: Aug 2012
Posts: 6,786
You probably won't see that 45 second figure drop more than 5 seconds with a higher hp motor. I agree that the higher hp motor will probably turn the prop faster, but 1/3 more power won't result in 1/3 more rpm. Even if it did increase by 1/3, prop performance is non linear with rpm. All of which means I doubt that you will get more than 10% less turning time.

And as Ski notes, check for barnacles and voltage at the motor first. Heavy barnacle growth doubles my turning time.

David
DavidM is online now   Reply With Quote
Reply

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


» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program





All times are GMT -5. The time now is 09:24 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012