Cruisers Forum
 


Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 11-01-2022, 19:06   #1
Registered User

Join Date: Jan 2022
Posts: 3
What hp to re-power a 38ft sailboat?

I need to re-power a 38ft sailboat (19,200lbs displacement, 10,200lbs ballast, 30ft LWL). A dealer mentioned that a Beta 25hp should be enough to reach hull speed. It seems underpowered. The boat is currently powered with a Westerbeke 4-107. Any view?
David97 is offline   Reply With Quote
Old 11-01-2022, 19:13   #2
Registered User

Join Date: Jan 2021
Posts: 35
Re: What hp to re-power a 38ft sailboat?

I'm sure you will get varied answers, but I have read that 3 to 4 hp per ton is the norm.
SV_Galateia is offline   Reply With Quote
Old 11-01-2022, 19:23   #3
Registered User

Join Date: Nov 2012
Boat: Kelly Peterson 46
Posts: 17
Re: What hp to re-power a 38ft sailboat?

25hp would probably get you to hull speed in calm conditions, but in any chop or wind your gonna suffer. I've heard the same as SV_Galateia, about 4hp per ton, so for you around 40hp should be good.
My boat is 20ish tons, I have 85hp
__________________
Jason
Kelly Peterson 46
www.svdontpanic.com
SVDontpanic is offline   Reply With Quote
Old 11-01-2022, 19:38   #4
Registered User
 
carlosproa's Avatar

Join Date: May 2011
Location: Miami
Boat: EDELCAT33
Posts: 590
Images: 2
Re: What hp to re-power a 38ft sailboat?

Quote:
Originally Posted by David97 View Post
I need to re-power a 38ft sailboat (19,200lbs displacement, 10,200lbs ballast, 30ft LWL). A dealer mentioned that a Beta 25hp should be enough to reach hull speed. It seems underpowered. The boat is currently powered with a Westerbeke 4-107. Any view?


Perkins 4-107 is anywhere from 40 to 50HP minus transmission and prop type. 25 HP is small, those high trust engines my do the trick but at a cost of speed. I assuming you are looking for an outboard? Can you reponer with a beta marine? I have my doubts on an outboard when is rough out there and the boat hobby horse. But each hull is different but lots of weight in one end of the boat…
carlosproa is offline   Reply With Quote
Old 11-01-2022, 20:16   #5
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29° 49.16’ N 82° 25.82’ W
Boat: Pearson 422
Posts: 16,144
Re: What hp to re-power a 38ft sailboat?

This doesn't sound like a light weight, performance boat so more HP to get reasonable results.

As noted 25 HP might get you there in a calm but motoring against wind and waves or trying to maneuver in crowded marina in with a current and a cross wind you would be sadly underpowered.

I had a 34' moderate displacement performance cruiser with a 35 hp engine and felt like that was just right. For your boat I wouldn't go any smaller than 40 hp. Max 45-46
__________________
The water is always bluer on the other side of the ocean.
Sometimes it's necessary to state the obvious for the benefit of the oblivious.
Rust is the poor man's Loctite.
skipmac is offline   Reply With Quote
Old 11-01-2022, 20:27   #6
Marine Service Provider
 
boatpoker's Avatar

Join Date: Nov 2008
Location: Port Credit, Ontario or Bahamas
Boat: Benford 38 Fantail Cruiser
Posts: 5,548
Re: What hp to re-power a 38ft sailboat?

Our 20,000lb. 38' fantail trawler has a 55hp and we cruise at 7.2 knots in calm water at 1800rpm. We can hit 8.2 knots if we run it up 3200rpm (and triple our fule usage from 0.75gph).
Attached Thumbnails
Click image for larger version

Name:	DIRT FREE mast avatar.jpg
Views:	160
Size:	60.6 KB
ID:	251061  
__________________
Your doubt does not negate my experience.
boatpoker is offline   Reply With Quote
Old 11-01-2022, 20:41   #7
Registered User
 
deblen's Avatar

Join Date: Oct 2014
Location: Grand Manan,N.B.,Canada N44.40 W66.50
Boat: Mascot 28 pilothouse motorsailer 28ft
Posts: 2,445
Images: 1
Re: What hp to re-power a 38ft sailboat?

Hull speed in calm conditions doesn't require much power.
Powering into rough seas or current requires much more.
Maneuvering or stopping smartly & safely requires much more plus a substantial propeller.
Around 40 HP IMHO.
__________________
My personal experience & humble opinions-feel free to ignore both
.
deblen is offline   Reply With Quote
Old 11-01-2022, 22:18   #8
Registered User
 
Searles's Avatar

Join Date: Feb 2020
Location: Port adelaide south australia
Boat: Cheoy lee perry 48
Posts: 381
Re: What hp to re-power a 38ft sailboat?

I would expect 25 to 35 up to be plenty ,depending on prop dia and pitch ,if plenty of room go for 3/1 gear box ,if you have a feathering prop all the better ,big prop turning slowly is the best way to go ,but not always possible,.⛵️⚓️
Searles is offline   Reply With Quote
Old 11-01-2022, 23:42   #9
Registered User
 
Celestialsailor's Avatar

Join Date: Nov 2006
Location: Back in Northern California working on the Ranch
Boat: Pearson 365 Sloop Westsail 28 and 14ft.Whitehall pulling skiff.
Posts: 9,427
Images: 5
Re: What hp to re-power a 38ft sailboat?

Welcome to the forum David. If you are going cruising, you will experience tides, currents and head winds. 40hp would be my minimum choice. A Beta 38 is you wanted to go that route. But honestly the Perkins 4-107 (40hp) is a great choice. The rebuilds are cheap and parts plentiful. Why not find a good rebuilder and go that route. Probably under $6K. A new Beta 38 would probably put you back around $15K. Plus no engine bed mods.
__________________
"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
Old 12-01-2022, 00:09   #10
Registered User

Join Date: Aug 2021
Location: PNW
Boat: 35 Ft. cutter, custom
Posts: 458
Re: What hp to re-power a 38ft sailboat?

Your boats size and displacement figures are a bit greater than mine.
I use 40hp, (not a Perkins,) and find it the ticket for being able to back-an-fill with authority, and easily cruise at low rpms with much quieter sound levels.
I'll agree with Celestialsailor, nothing wrong with a Perkins,
The newer rebuilds of 107s/108s are better than the old ones.
Front end drives are better, and most important they don't leak oil, (at least I heard that).
Bowdrie is offline   Reply With Quote
Old 12-01-2022, 01:39   #11
Registered User

Join Date: Apr 2013
Posts: 10,328
Re: What hp to re-power a 38ft sailboat?

What did the manufacturer spec?

Also, how much would you expect to save downgrading from 40hp to 25hp...it won't make any noticeable difference in fuel efficiency.
valhalla360 is offline   Reply With Quote
Old 12-01-2022, 03:48   #12
Registered User

Join Date: Sep 2011
Posts: 147
Re: What hp to re-power a 38ft sailboat?

Quote:
Originally Posted by David97 View Post
I need to re-power a 38ft sailboat (19,200lbs displacement, 10,200lbs ballast, 30ft LWL). A dealer mentioned that a Beta 25hp should be enough to reach hull speed. It seems underpowered. The boat is currently powered with a Westerbeke 4-107. Any view?
Would you buy a 38' boat with a 25hp engine? I wouldn't.
Put a beta 60(54hp) in, the next guy will pay for it.
Caleb_Grey is offline   Reply With Quote
Old 12-01-2022, 05:27   #13
Senior Cruiser
 
GordMay's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 46,434
Images: 241
Re: What hp to re-power a 38ft sailboat?

Greetings and welcome aboard the CF, David.

There’s plenty of opinions, expressed here [including mine, FWIW]:
https://www.cruisersforum.com/forums...ze-1577-2.html

A rough Rule of thumb for determining Horsepower Required for a Sailboat : one horsepower per 500 pounds ( ± 50lbs ) loaded.

Westerbeke Corporation suggests 2 hp for every 1,000 lb of displacement for coastal cruising, and 2.5 hp per 1,000 lb of displacement for offshore. That would mean a 38 ft. sailboat with a displacement of 15,000 lb should have a 30 hp engine for coastal cruising and a 37.5 hp engine for offshore.
In your case: 15 Long Tons = 33600#
Hence: 33. x 2 = 67.2 HP ~or~ 33.6 x 2.5 = 84 HP.

In their book "The Gougeon Brothers on Boat Construction" the authors suggest a good rule-of-thumb is 1 hp for every 500 lb of displacement... that would mean 38 ft. sailboat with a displacement of 15,000 lb should have a 30 hp engine.
In your case 33 x 2 = 66 HP

Some people suggest 1 hp for every ft. of boat waterline length... that would mean a 38 ft sailboat with a waterline length of 30 ft should have a 30 hp engine.
In your case 41 x1 = 41 HP

Some people suggest 3 - 5 hp (continuous rating) per long ton (to calculate the boat's weight in long tons divide the displacement by 2,240)... that would mean a boat with a displacement of 15,000 lb should have a 20 - 33 hp engine. For offshore conditions some people suggest the engine be larger than the size calculated for coastal cruising, possibly + 25%... so in this example the engine size would be increased to 25 - 41 hp respectively.

How do you measure horsepower?
Power is a measurement of the ability to do a unit of work in a specific time. It is calculated, not measured. Horsepower and watts (kilowatts are 1,000s of watts) are units of power. Power is calculated by measuring engine torque at a specific crankshaft rpm and multiplying the 2 figures together.

Engine Horsepower/Torque Formulae

Horsepower = ( Torque in Lb/Ft x Crankshaft Speed in RPM ) ÷ 5252

Power = Torque X RPM
Torque = Power ÷ RPM
RPM = Power ÷ Torque
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 12-01-2022, 05:48   #14
Marine Service Provider

Join Date: Jan 2019
Boat: Beneteau 432, C&C Landfall 42, Roberts Offshore 38
Posts: 4,087
Re: What hp to re-power a 38ft sailboat?

Speaking from hard earned experience...a 25 hp diesel in a 38' boat simply won't cut it.

Sure, you'll move the boat, but not at hull speed.

Engine hp is only one aspect, blade diameter, pitch, number of blades, transmission reduction, etc, etc, all play a part.

You really wanna learn?

Get the " Propellor Handbook" authored by Dave Gerr, will give you every tool you need to determine engine hp.

My suggestion would be nothing less than 40 hp....
MicHughV is offline   Reply With Quote
Old 12-01-2022, 05:56   #15
Moderator
 
tkeithlu's Avatar

Cruisers Forum Supporter

Join Date: Feb 2012
Location: Carrabelle, Florida
Boat: Fiberglas shattering 44' steel trawler
Posts: 5,145
Re: What hp to re-power a 38ft sailboat?

To bring up another point, David, installing a different engine in the same compartment can be a nightmare - all the hoses, seacocks, cables, engine mounts, and wiring are in the wrong places even if the compartment space allows for the new engine at all. There are strong reasons to either rebuild the existing engine or replace with an identical engine.

Consensus seems to be that your 40 HP is about right.
__________________
Never let anything mechanical know that you are in a hurry.
tkeithlu is offline   Reply With Quote
Reply

Tags
boat, sail, sailboat

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
Want To Buy: 34-38ft blue water sailboat <40K New England ShelleySailor Boats For Sale and Wanted 18 02-04-2021 20:26
Want To Buy: 28-38ft Sailboat with raised saloon near SF for $15-20k coldfish Boats For Sale and Wanted 17 08-09-2019 09:06
Are Irwins (38ft) Blue Water Capable? jama Meets & Greets 4 19-09-2009 18:03

Advertise Here


All times are GMT -7. The time now is 13:44.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2022, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2022, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.