Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 03-09-2011, 14:39   #1
Registered User
 
Surveyor's Avatar

Join Date: Mar 2010
Location: Ft. Pierce, FL - Bislig, Philippines - Gladstone QLD
Boat: 1968 Alberg 30 #329
Posts: 451
Diesel - Two Cylinder vs Three Cylinder

Background: I am about to install engine motor mount beds in my Alberg 30.

Reason for asking: I have read that a 2 cylinder diesel will vibrate more than a 3 cylinder.

Comment: I have procured a 16hp Beta (2cyl) but it is not too late to upgrade to a 20hp (3cyl). The engine has not yet been shipped. The 16 will push my slow boat at hull speed but at a higher rpm in relation to the 20hp with nearly the same fuel consumption. The only experience I have with diesels of this size are diesel light plants and they are all 2 cyl and do vibrate heavily until they get going. Vibration is a concern because I am installing the beds myself and I want to be sure I dont pay for something I hate later or on the other hand paid too much for.

Questions: Is there a notable difference in vibration between Beta (or any other) 2 cyl engines and 3 cyl engines? Should I be concerned?

Thank you in advance,
__________________

__________________
Jim - Bahala na!
http://svcookie.blogspot.com/
KK4GGF
Surveyor is offline   Reply With Quote
Old 03-09-2011, 14:49   #2
Registered User

Join Date: Aug 2006
Posts: 37
Re: Diesel - 2cyl vs 3cyl

I would go for the 3 cly. They are much smother. I went from 3-4 cyl on my repower and glad I did. Don't think 20 hp would be overpowering your 30 ft.
__________________

__________________
saben is offline   Reply With Quote
Old 03-09-2011, 14:58   #3
Registered User

Join Date: Jan 2011
Location: PNW
Boat: custom teak ketch 48' Eastwind
Posts: 607
Images: 9
Re: Diesel - 2cyl vs 3cyl

by all means - go for the 3 banger - much smoother! You'll be glad to have the extra HP for not much more weight. Most 3, 5 & 6 cylinder engines run smoother than 2 & 4 cyl engines no matter who's it is.
__________________
Geoduck is offline   Reply With Quote
Old 03-09-2011, 15:05   #4
Registered User

Join Date: May 2009
Location: NJ, Paris FR and, for the moment, Cape Coral FL
Boat: Islander Freeport 41, AEGEA
Posts: 186
Re: Diesel - 2cyl vs 3cyl

HUGE difference. A 2 cylinder engine can hang up if the piston rods stop in the up and down position. If this happens the piston pushes straight across the crankshaft and doesn't move. To eliminate this the crankshaft has to have the throws placed a few degrees off 180 degrees, let's say 185 and 175 degrees apart.. The power pulses come in an irregular sequence that sets up a harmonic that vibrates a lot. A 3 cylinder has the throws placed 120 degrees apart and can't lock up, so you get the power pulses at a nice even pace.

Dick Pluta
AEGEA
__________________
Dick Pluta is offline   Reply With Quote
Old 03-09-2011, 17:59   #5
Senior Cruiser
 
Starbuck's Avatar

Cruisers Forum Supporter

Join Date: May 2005
Location: Long Beach, CA
Posts: 827
Don't Be Penny Wise, But Dollar Foolish

20 hp is not too much for your boat. You'll be glad you have it the first time you motor into a swell and headwind.

And you'll be glad you have it every time you start it and your coffee cup doesn't dance to the edge of the table.

A little more money up front, and nearly the same fuel consumption, for significantly smoother operation, and confidence in your pocket for snotty conditions = win.
__________________
s/y Elizabeth Catalina 34 MkII
"Man must have just enough faith in himself to have adventures, and just enough doubt of himself to enjoy them." G. K. Chesterfield
Starbuck is offline   Reply With Quote
Old 03-09-2011, 21:18   #6
Registered User
 
S/V Alchemy's Avatar

Join Date: May 2008
Location: Toronto
Boat: Custom 41' Steel Pilothouse Cutter
Posts: 4,576
Re: Diesel - 2cyl vs 3cyl

Get the 3-cylinder (if it will fit as easily, and then you can throw in a nice big alternator for faster charging without worrying you're "parasitizing" your thrust.

I don't know how the Alberg 30 is for engine "cave" space, but if you have to, consider cutting panels on the sides if needed for the different engine.
__________________
S/V Alchemy is offline   Reply With Quote
Old 03-09-2011, 21:37   #7
Registered User
 
markpierce's Avatar

Join Date: Aug 2010
Location: Central California
Boat: M/V Carquinez Coot
Posts: 3,413
Re: Diesel - 2cyl vs 3cyl

I always liked the sound of one-cylinder engines and thought that was how "real" boats sound.
__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 04-09-2011, 13:39   #8
Registered User
 
Hydra's Avatar

Join Date: May 2009
Location: Lorient, Brittany, France
Boat: Gib'Sea 302, 30' - Hydra
Posts: 1,229
Re: Diesel - 2cyl vs 3cyl

On my 30', 3.5t boat, I have a 2-cyl Nanni 2.50 HE engine, made on the same Kubota base as the Beta. IME, it runs fairly smoothly.

However, it is rated at 14HP and I find the boat slightly underpowered, e.g. for maneuvering in windy conditions. Unfortunately, there is no space for a (longer) 3-cyl engine (and no money, either).

Alain
__________________
Hydra is offline   Reply With Quote
Old 04-09-2011, 14:12   #9
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,750
Re: Diesel - 2cyl vs 3cyl

Quote:
Originally Posted by Geoduck View Post
by all means - go for the 3 banger - much smoother! You'll be glad to have the extra HP for not much more weight. Most 3, 5 & 6 cylinder engines run smoother than 2 & 4 cyl engines no matter who's it is.
Well, a 3 cylinder is not smoother than a 4. But a 3 cylinder engine has a nice loping rhythm. It's incomparably better than a twin. Go for the 3.
__________________

__________________
Dockhead is online now   Reply With Quote
Reply

Tags
diesel

Thread Tools
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
Cummins Diesel Twin 500hp QSC8.3 Permanent Slow Speed ASKAER Engines and Propulsion Systems 15 10-10-2011 13:15
Diesel RIB Tenders . . . The Holy Grail ? capcook Auxiliary Equipment & Dinghy 3 02-09-2011 23:06
Do Not Use Biocide Journeyman Engines and Propulsion Systems 37 24-07-2011 19:47
For Sale: 3.5kw Diesel Marine Genset, Kubota Power, Ultra-Compact MoonlightSailor Classifieds Archive 0 18-07-2011 21:28
Long Way from Home - Diesel Trouble Tia Bu Engines and Propulsion Systems 17 29-06-2011 17:22



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 22:03.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.