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 24-09-2018, 06:11   #1
Registered User

Join Date: Sep 2016
Location: NSW, Australia
Boat: Simpson 12
Posts: 149
Which engine for my dinghy?

Hi, I am building myself a catamaran tender for our liveaboard 12m catamaran that my family (2 adults, 2 kids) will be living on from early next year (Link to the plans. I'm building the 3.2m).

The designer of the tender says the max power is 15HP. Since 2 stroke engines are pretty much banned in Australia, I am looking at 4 strokes.

Every 4 stroke engine that I have researched (suzuki, yamaha, honda, tohatsu) in the 15HP range is basically a cut down version of the 20HP. This means that the 15HP is the same weight and practically the same price as it's 20HP big sister.

Why wouldn't I get the 20HP engine? Isn't more power always going to be better? Fully loaded with provisions and the whole family we could probably plane back to the mother ship. With 20HP I could drag the kids on a donut and have a passenger watching on.

Why limit myself to 15HP?
fursoc is offline   Reply With Quote
Old 24-09-2018, 06:39   #2
Moderator Emeritus
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,348
Which engine for my dinghy?

I didn’t.
Your building one, so it’s up to you to determine what is safe and what isn’t.
a64pilot is offline   Reply With Quote
Old 24-09-2018, 07:17   #3
cruiser

Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
Re: Which engine for my dinghy?

May want to be careful opening the throttle all the way, especially with kids aboard.
john61ct is offline   Reply With Quote
Old 24-09-2018, 07:24   #4
Registered User
 
admiralslater's Avatar

Join Date: Sep 2014
Location: Toronto summer rest somewhere else
Boat: Outremer 45/pdq36
Posts: 1,170
Re: Which engine for my dinghy?

The advantage of a hard bottom dingy is that you dont need a ot of horsepower for a good speed . I would go with somthing smaller for that boat maybe 6-8 . Also that size of motor can be man handled
__________________
“Growing older but not up”
admiralslater is offline   Reply With Quote
Old 24-09-2018, 07:46   #5
Registered User
 
travellerw's Avatar

Join Date: Jan 2014
Location: Martinique
Boat: Fortuna Island Spirit 40
Posts: 2,298
Re: Which engine for my dinghy?

Personally I would see if you could borrow a couple of motors before making your purchase. I think you might be shocked at how easily the hard dink is pushed.

If I was a betting man, I would guess you will find a 9.8Hp more than adequate.
travellerw is offline   Reply With Quote
Old 24-09-2018, 09:21   #6
Registered User
 
admiralslater's Avatar

Join Date: Sep 2014
Location: Toronto summer rest somewhere else
Boat: Outremer 45/pdq36
Posts: 1,170
Re: Which engine for my dinghy?

Quote:
Originally Posted by travellerw View Post
Personally I would see if you could borrow a couple of motors before making your purchase. I think you might be shocked at how easily the hard dink is pushed.

If I was a betting man, I would guess you will find a 9.8Hp more than adequate.
I agree
__________________
“Growing older but not up”
admiralslater is offline   Reply With Quote
Old 24-09-2018, 09:45   #7
Senior Cruiser
 
John_Trusty's Avatar

Cruisers Forum Supporter

Join Date: Oct 2014
Location: Attached to a mooring ball in Jensen Beach FL, until...
Boat: Leopard 40 2009
Posts: 643
Re: Which engine for my dinghy?

I've seen issues with dingy engines that only one crew member can operate. If only "dad" can mount it on the dingy (if taken off for passage), or start the pull-start, then dad has to do this task. In an emergency, or just convenience for who does things when arriving, sometimes dad is not available. Think about future use.
__________________
John Trusty

Better to trust the man who is frequently in error than the one who is never in doubt." -- Eric Sevareid
John_Trusty is offline   Reply With Quote
Old 24-09-2018, 09:50   #8
Registered User

Join Date: Jun 2017
Posts: 85
Re: Which engine for my dinghy?

I had the same dilemma for my 11ft dingy. We had a 15 hp Yamaha. The 20hp Suzuki is fuel injected. In fact it’s the only remote steering 20 hp w/o a carburetor. The motor is great very fuel efficient and even has pull start should the battery fail. The only down side it’s only available with a long leg so I needed to add a riser block. Couldn’t be happier
vanderd is offline   Reply With Quote
Old 24-09-2018, 10:14   #9
Registered User
 
LeeV's Avatar

Join Date: Apr 2013
Location: Md
Boat: 2013 FP Lipari 41
Posts: 1,307
Re: Which engine for my dinghy?

Torqeedo? If you’re building in foam and don’t need the “zoom,” it may suffice, as well as being green (no fuel, battery...).
__________________
LeeV
Lipari 41
s/v AMERICAN HONEY
LeeV is offline   Reply With Quote
Old 24-09-2018, 10:41   #10
Registered User
 
jkindredpdx's Avatar

Join Date: May 2011
Location: Portland, OR, USA
Boat: Hallberg Rassy 35'
Posts: 1,200
Images: 5
Re: Which engine for my dinghy?

I use an electric with a couple lawnmower batteries... It's nice because it is light and easy to handle. It always starts as long as the battery is charged, that's why I have two batteries. I have a small solar panel to keep the batteries topped off. I don't have any gasoline onboard... just diesel.
__________________
https://www.sednahr35.blogspot.com/ Jim K.
jkindredpdx is offline   Reply With Quote
Old 24-09-2018, 12:19   #11
Registered User
 
S/V Alchemy's Avatar

Join Date: May 2008
Location: Nova Scotia until Spring 2021
Boat: Custom 41' Steel Pilothouse Cutter
Posts: 4,976
Re: Which engine for my dinghy?

Quote:
Originally Posted by admiralslater View Post
I agree

There is also the element of a short leg reducing weight and the beauty of a properly pitched prop. If said dink is always going to be cargo and passengers, you don't want speed. You want thrust. You figure out what HP from there. We have a 50 pound Portabote that goes 4 knots with a Honda 2.3 HP air cooled engine that my compact wife can one-arm onto the transom. That suits us as we are never in that much of a hurry with jerry cans, groceries and other shoreside stuff. Your mileage, pun aside, may vary, but 15 HP is a lot of power for a hard dink.
__________________
Can't sail? Read about our travels at https://alchemyonpassage.blogspot.com/. Can't sleep? Read www.alchemy2009.blogspot.com for fast relief. Can't read? Avoid www.volumesofsalt.blogspot.com, because it's just personal reviews of sea books.
S/V Alchemy is offline   Reply With Quote
Old 24-09-2018, 12:40   #12
Registered User

Join Date: Apr 2012
Location: N Palm Beach
Boat: Catalac 12 M
Posts: 40
Re: Which engine for my dinghy?

I had a 10 foot hard dingy and a 2 cycle 15 hp. I pulled the kids many hours behind the boat until they got into there early teens.
DrDelmas is offline   Reply With Quote
Old 24-09-2018, 12:55   #13
Registered User

Join Date: Jul 2014
Location: Hawaii
Boat: Jeanneau SO DS 49
Posts: 356
Re: Which engine for my dinghy?

Thats a small dingy for 4 people. A rib with large tubes will have 3x the capacity per ft and not take waves over the bow. I did see an inflatable cat tender 12', 18" tubes, trampoline. and sailing rig. Looked good to me.
A daily problem is trying to open a spot at the dingy dock with 2 hulls. Stepping onboard by the bow with so little buoyancy.
I used to row my 12' hobie cat to shore daily, thinking it was faster than a mono hard dingy but couldn't keep up with the girl on the mooring next to me in her 8' ply tender.
More relevant to your question, an electric trolling motor will push you along nicely. As you won't plane, small and light is best.
SteveSadler is offline   Reply With Quote
Old 24-09-2018, 13:36   #14
Moderator Emeritus
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,348
Re: Which engine for my dinghy?

His point is I believe that using the Suzuki as an example, the 9.9, 15 and 20 HP are all the same motor and all weigh 99 lbs.
So yes you may can get by with a 9.9, but why not have twice the HP for exactly the same weight?
I don’t understand why people keep saying, oh no, it might be unsafe at full throttle.
I can absolutely tell you that if I were to run my Wife’s car at full throttle it would be unsafe as it would be approaching 200 MPH.
However we don’t, we enjoy the acceleration at times, but have enough sense to not run wide open.
Why can’t people accept the same for a dinghy?
a64pilot is offline   Reply With Quote
Old 24-09-2018, 16:57   #15
Registered User
 
finefurn's Avatar

Join Date: Jan 2013
Location: Mason, NH
Boat: 1984 Hunter 27
Posts: 120
Re: Which engine for my dinghy?

For a Dinghy I 'd put more focus on weight than horsepower. Are you you going to tow the dinghy when underway with the mother ship, and mount the motor on the rail of your mother ship. In a mooring field you don't want to be throwing up a wake so speed is not necessarily a desirable thing. We have a 10 ft hard bottom inflatable with the Honda 2.3 weights 29 lbs. I had a Mercury 5 hp that I gave to my son that weighed easily twice as much. Much happier with the 2.3 hp
finefurn is offline   Reply With Quote
Reply

Tags
dinghy, engine

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
Which engine oil to use on BMW D12 marine diesel engine gawie Engines and Propulsion Systems 19 17-12-2015 18:00
Which Is Red, Which Is Black ? night0wl Electrical: Batteries, Generators & Solar 29 15-03-2014 22:30
Which Hulls Can Be Safely Beached, and Which Must Be Hauled ? toby24b Multihull Sailboats 22 16-01-2014 17:41
Which Is Which ? Peter Richardso Multihull Sailboats 32 29-08-2011 11:32
Which Docks Are Which in Ensenada ? deinno Our Community 6 03-08-2011 10:26

Advertise Here


All times are GMT -7. The time now is 07:40.


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.