Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 28-07-2006, 02:04   #1
Registered User

Join Date: Feb 2006
Posts: 192
Which engine?

New boat (38ft cat, slim hulls) with standard twin 20HP, optional 30, 40HP. Which to go for? difficult to change later....

One argument: 20HP lighter, less gph, adequate performance, Autoprop would give extra power when punching into seas/headwind as it auto-pitches (and that is the only time you may need it) so spend less on Autoprop and go with smaller engine.

Other argument: 30Hp allows cruising at lower revs, better passage making on one engine, extra power for motoring into bad weather, but probably only half knot faster and extra weight/expense

Use will be blue water cruising

Any experience/thoughts?
__________________

__________________
Moby Dick is offline   Reply With Quote
Old 28-07-2006, 03:50   #2
Senior Cruiser
 
Talbot's Avatar

Cruisers Forum Supporter

Join Date: Jun 2004
Location: Brighton, UK
Boat: Privilege 37
Posts: 3,579
Images: 32
first query would be how well does she sail to windward?
What is the weight difference between the engine choices,


I suspect (not knowing which boat), that I would choose the middle option, and would also fit autoprops.
__________________

__________________
"Be wary of strong drink. It can make you shoot at tax collectors - and miss."
Robert A Heinlein
Talbot is offline   Reply With Quote
Old 28-07-2006, 04:07   #3
Registered User
 
Jon D's Avatar

Join Date: Sep 2004
Location: Ft. Lauderdale, FL currently CLODs [cruisers living on dirt]
Posts: 423
Images: 11
Also remember large alternators, refer compressors, etc use HP. The larger the engine the more HP you have for the add-ons that a full time cruiser will need and put on. IMHO you can't get hurt with extra HP also diesel tankage options to correct for the higher burn rate.
__________________
Jon
S/Y Sirius
Moody 47
Jon D is offline   Reply With Quote
Old 28-07-2006, 05:00   #4
Registered User

Join Date: Jun 2005
Posts: 1,901
Please define the engine model choices. HP rating isn't enough for me to accuratly recomend an engine. Knowing which model, might make a difference in servicability.
__________________
never monday is offline   Reply With Quote
Old 28-07-2006, 05:24   #5
Registered User

Join Date: Feb 2006
Posts: 192
Engines are Volvo saildrives.
Standard fit are 115A alternators (one per engine)
Sails pretty well to weather for a mini-keel cat - points to 35deg in flat water
Engines under bunks

30HP with Autoprops has a significant cost penalty, if not really needed. And weight of course.

Thanks

MD
__________________
Moby Dick is offline   Reply With Quote
Old 28-07-2006, 06:59   #6
Registered User
 
Strygaldwir's Avatar

Join Date: Dec 2004
Location: Deale, Maryland
Boat: SeaView - Privilege 37
Posts: 1,020
Images: 5
My leaning would be to get the 30 horse now. Keep the standard props. It is much easier to change the props if you need them, than replace engines. Is there that much difference in overall weight between the 20 and 30 hp options? Twin 40s for a smallish cat (under 40 feet) seems a bit HIGH. 30s should drive you up to hull speed.
__________________
Strygaldwir is offline   Reply With Quote
Old 28-07-2006, 07:28   #7
Registered User

Join Date: Feb 2006
Posts: 192
Thanks for opinions. Volvo omit the weight of the 30HP units, but extrapolating from the 12 and 30HP engines (weight given) I would expct about a 50lb differenec between 20 and 30HP, consumption 5.5gph versus 7gph (at same cruising speed).

3k difference in purchase price (and I would need SOME sort of folding prop anyway)
__________________
Moby Dick is offline   Reply With Quote
Old 28-07-2006, 07:33   #8
Senior Cruiser
 
Vasco's Avatar

Cruisers Forum Supporter

Join Date: Apr 2004
Location: Toronto
Boat: CS36Merlin, "La Belle Aurore" Ben393 "Breathless"
Posts: 7,138
I know we're talking two engines but isn't that consumption kind of high? My 30hp (3GM30F) uses about 1/2 gallon per hour at cruising speed about 2500 rpm.
__________________
Rick I
Toronto in summer, Bahamas in winter.
http://groups.yahoo.com/group/beneteau393/
Vasco is offline   Reply With Quote
Old 28-07-2006, 07:47   #9
Registered User

Join Date: Feb 2006
Posts: 192
yeh, a bit high by a factor of ten.... I meant aound 0.55 and 0.7 GPH (per engine, going by Volvo graph at 2300RPM)

Incidently, the new Volvo D1 series claims 3-4db drop in noise, and 115A alternator with electronic sensor that delivers 35A at idle and 100+A at cruising speed. That seems pretty good (if manufaturers claims can be beleived)?

MD
__________________
Moby Dick is offline   Reply With Quote
Old 28-07-2006, 08:01   #10
jzk
Registered User

Join Date: Jun 2006
Posts: 639
Is there any way to avoid getting a saildrive? They are nothing but problems. Gunboat has stated they will never put another saildrive in one of their boats.
__________________
jzk is offline   Reply With Quote
Old 28-07-2006, 08:38   #11
Registered User

Join Date: Feb 2006
Posts: 192
Hi JZK
Not without making a production cat into a semi-custom job (and $$). Anyway, most cats made (at this size) are saildrive-equiped. I dont think what Gunboat say has much relevance to me or my needs - they are in a different world. 'Standard' drives have their problems too.
__________________
Moby Dick is offline   Reply With Quote
Old 28-07-2006, 09:11   #12
jzk
Registered User

Join Date: Jun 2006
Posts: 639
Quote:
Originally Posted by Moby Dick
Hi JZK
Not without making a production cat into a semi-custom job (and $$). Anyway, most cats made (at this size) are saildrive-equiped. I dont think what Gunboat say has much relevance to me or my needs - they are in a different world. 'Standard' drives have their problems too.
I have just seen nightmare after nightmare with Saildrives. If Gunboat said the problem was the extra weight, then their point would be irrelevant. They don't like them because they are crap.
__________________
jzk is offline   Reply With Quote
Old 28-07-2006, 09:23   #13
Senior Cruiser
 
Vasco's Avatar

Cruisers Forum Supporter

Join Date: Apr 2004
Location: Toronto
Boat: CS36Merlin, "La Belle Aurore" Ben393 "Breathless"
Posts: 7,138
Quote:
Originally Posted by Moby Dick

Incidently, the new Volvo D1 series claims 3-4db drop in noise, and 115A alternator with electronic sensor that delivers 35A at idle and 100+A at cruising speed. That seems pretty good (if manufaturers claims can be beleived)?

MD
Don't get me started on Volvos!!
__________________
Rick I
Toronto in summer, Bahamas in winter.
http://groups.yahoo.com/group/beneteau393/
Vasco is offline   Reply With Quote
Old 28-07-2006, 09:31   #14
Registered User

Join Date: Feb 2006
Posts: 192
Its not just weight. Gunboat have a weight v. space v. cost v. 'effectiveness' * priority relationship that is different to mine.

*effectiveness: I mean how good the solution is at the job it is intended for
__________________
Moby Dick is offline   Reply With Quote
Old 28-07-2006, 09:45   #15
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Moby Dick,

I'm a monohull sailor with little experience on cats. However, I've observed them and sailed with them for many years in the Caribbean. Here's my take.

1. Cruising cats are very easily weighted down due to the necessities of cruising. This GREATLY degrades their performance, especially to windward.

2. With my 42' monohull, I've very often left cats behind in a breeze, and even beat them sailing upwind when they had both engines going in the Drake Channel.

3. More power is better, not just because of the extra stuff you hang on the engines for cruising, but because cruising cats typically are dogs to windward and in a chop, and need the extra power avoid getting stopped by headseas.

4. I would echo earlier posts re: Volvos and saildrives. Avoid them at all costs. If you choose to go with them anyway, you're forewarned.

Good luck.

Bill
S/V Born Free
__________________

__________________
btrayfors is offline   Reply With Quote
Reply

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
Basic Engine Gauge Theory and Testing GordMay Electrical: Batteries, Generators & Solar 12 20-10-2015 09:54
Corroding Engine mounts ccannan Engines and Propulsion Systems 6 29-09-2015 00:13
Yanmar Tips GordMay Engines and Propulsion Systems 18 29-07-2012 06:04
Need a diesel "intro" for the Admiral chuckiebits Engines and Propulsion Systems 3 05-06-2006 11:09
Engine Diagnostic Charlie Engines and Propulsion Systems 22 22-04-2006 16:28



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 10:16.


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.