Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 30-09-2014, 19:01   #1
Registered User

Join Date: Oct 2011
Posts: 10
Isolating Diesel Engine From Propellar

Hi,
I have a bad electrolisis problem on my steel sailboat , I have Hauled the boat to my yard to repair the damage (holes) and determine why the problem occured in the first place, my diesel engine was grounded to the hull , was this a mistake? I don`t have the isolating connection and bolt sleeves between shaft and and tranny, where could I get one of these? also should my aluminum mast be in contact with my steel hull?
I would also like to thank the people who replied to a previous post for help with this problem, BUT.......I can`tfind that place to thank them
So thank you in advance, you are all great people and very willing to help an old sailor with a problem (don`t do computers very well)

Ed Gushue, sailing Yawl "Estrellita IV "
roaminraulf is offline   Reply With Quote
Old 01-10-2014, 08:37   #2
Marine Service Provider

Join Date: Aug 2008
Location: North Carolina
Posts: 290
Re: Isolating Diesel Engine From Propellar

To stop a steel boat from wasting away I suggest that you use an isolated ground electrical system. This way the engine is inert electrically and you wont have the problems that you are now having.

Stanley
NCboatrx is offline   Reply With Quote
Old 03-10-2014, 20:42   #3
Registered User

Join Date: Oct 2011
Posts: 10
Re: Isolating Diesel Engine From Propellar

Thank you Stanley,yes I have been told that is the thing to do,
roaminraulf is offline   Reply With Quote
Old 05-10-2014, 03:22   #4
Registered User

Join Date: Mar 2009
Location: Australia, Hervey Bay QLD
Boat: Boden 36 Triple chine long keel steel, named Nekeyah
Posts: 909
Re: Isolating Diesel Engine From Propellar

I doubt that this on its own would cause your problem. Our engine is connected to the negative side of our electrical system and has been for over 20 years no problems.
When the boat is not being used, there are switches that isolate the battery at each pole.
I suppose you could use an above ground alternator and also connect the negative line to your starter through a relay but you will still have to replace the oil pressure and temp senders with isolated units if you can get them.
This should not be necessary if you find the current leakage that is causing the problem.

Regards,
Richard.
boden36 is offline   Reply With Quote
Old 05-10-2014, 05:12   #5
Registered User
 
sanibel sailor's Avatar

Join Date: Feb 2013
Location: Ocala FL
Boat: 1979 Bristol 35.5 CB
Posts: 1,953
Re: Isolating Diesel Engine From Propellar

Aren't these usually shore power issues?
__________________
John Churchill Ocala, FL
NURDLE, 1979 Bristol 35.5 CB
Currently hauled out ashore Summerfield FL for refit
sanibel sailor is offline   Reply With Quote
Old 05-10-2014, 05:50   #6
Registered User

Join Date: Oct 2011
Posts: 10
Re: Isolating Diesel Engine From Propellar

Thank You John for the reply, one "expert" told me that 99.9 per cent of the time on boats that he has investigated , the problem was on board,
roaminraulf is offline   Reply With Quote
Old 05-10-2014, 07:09   #7
Registered User
 
sanibel sailor's Avatar

Join Date: Feb 2013
Location: Ocala FL
Boat: 1979 Bristol 35.5 CB
Posts: 1,953
Re: Isolating Diesel Engine From Propellar

Quote:
Originally Posted by roaminraulf View Post
Thank You John for the reply, one "expert" told me that 99.9 per cent of the time on boats that he has investigated , the problem was on board,
yes, the vessel's shore power arrangement. Do you have Calder's Mech/Elec book?
__________________
John Churchill Ocala, FL
NURDLE, 1979 Bristol 35.5 CB
Currently hauled out ashore Summerfield FL for refit
sanibel sailor is offline   Reply With Quote
Old 05-10-2014, 07:24   #8
Marine Service Provider

Join Date: Mar 2014
Location: UK and Central America
Boat: Tucker CA41 Steel 40 foot Ketch
Posts: 402
Re: Isolating Diesel Engine From Propellar

I also have a steel boat which has a negative floating DC supply . e.g. negative is not connected to sea water.

When we bought the the boat we had electrolysis problems (heat exchangers, propeller, shaft) that we spent a few years sorting out, mainly by rewiring carefully,

We ended up fitting carbon brushes to the prop shaft to ground it out, see Product Catalogue - Marine Cathodic Protection - MGDUFF

I also came across the following link whilst I was looking for the MgMacDuff thing

http://www.cruisersforum.com/forums/...ver-56582.html

Good luck
Triumphant is offline   Reply With Quote
Old 05-10-2014, 08:37   #9
Registered User
 
Sailorlou's Avatar

Join Date: Oct 2008
Location: Paradise Village, MX
Boat: Pearson 367, 36 Foot
Posts: 62
Re: Isolating Diesel Engine From Propellar

Do you connect to shore power when at the dock and if so do you have an isolation transformer between the shore power and your boat?
Sailorlou is offline   Reply With Quote
Old 05-10-2014, 09:59   #10
Registered User
 
Celestialsailor's Avatar

Join Date: Nov 2006
Location: Back in Northern California working on the Ranch
Boat: Pearson 365 Sloop and 9' Fatty Knees.
Posts: 10,466
Images: 5
Re: Isolating Diesel Engine From Propellar

Quote:
Originally Posted by roaminraulf View Post
Hi,
I have a bad electrolisis problem on my steel sailboat , I have Hauled the boat to my yard to repair the damage (holes) and determine why the problem occured in the first place, my diesel engine was grounded to the hull , was this a mistake?
Yes...that is diffenately a mistake. You have essentially created a path from a D.C. negative (ground) to sea water and back to D.C. positive back through the sending units on the engine. the prop shaft is insolated by the cutlass bearing and the engine should be isolated vis the rubber isolatic mounts. So I am assuming you connected a cable from the engine to the hull. If so, remove it and ground the casting of the engine directly to the battery negative gang post. this will isolate the path. To check the system for other grounds to hull, you can put a volt meter from the hull itself to the positive terminal on the batteries. There should be no reading.

Quote:
Originally Posted by boden36 View Post
I doubt that this on its own would cause your problem. Our engine is connected to the negative side of our electrical system and has been for over 20 years no problems.
I am assuming the connection from the engine goes directly back to the negative battery and not through the hull.

Regards,
Richard.
Quote:
Originally Posted by Triumphant View Post
I also have a steel boat which has a negative floating DC supply . e.g. negative is not connected to sea water.
Exactly
__________________
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming: Wow - what a ride!"
Celestialsailor is offline   Reply With Quote
Reply

Tags
diesel, engine, rope

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Isolating Transformers, The Earth wire connection conundrum goboatingnow Electrical: Batteries, Generators & Solar 331 04-11-2013 20:29
Isolating Transformer earth output Fuss Electrical: Batteries, Generators & Solar 10 15-03-2013 15:53
Isolating that Mysterious Leak . . . OrangeCrush Monohull Sailboats 8 04-05-2012 10:17
Battery Isolator - or isolating switches ribbony Electrical: Batteries, Generators & Solar 10 22-02-2008 14:39
isolating / charging batteries? Doghouse Electrical: Batteries, Generators & Solar 5 09-08-2006 13:08

Advertise Here


All times are GMT -7. The time now is 14:13.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.