Cruisers Forum
 


Join CruisersForum Today

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 08-02-2017, 22:14   #1
Registered User

Join Date: Dec 2014
Posts: 163
Twin outboards on tender

My rib 10' has a 3hp merc and ticks along ok.... but more power is often thought wanting.
Trouble is I don't want to go heavier outboard for lifting and stowing so I was thinking... twin 3hp mercs?
Anyone tried this approach?
Any reason why it may be a bad idea?
Would it provide similar performance to a single 6hp?
__________________

nzmal is offline   Reply With Quote
Old 08-02-2017, 22:16   #2
Senior Cruiser
 
44'cruisingcat's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 9,068
Images: 69
Re: Twin outboards on tender

A single 6 will greatly outperform twin 3's.
__________________

__________________
"You CANNOT be serious!"


John McEnroe
44'cruisingcat is offline   Reply With Quote
Old 08-02-2017, 22:55   #3
Registered User
 
MikeFergie's Avatar

Join Date: Mar 2015
Location: Mozambique
Boat: Leopard 40 (2009) & Crownline 250CR
Posts: 281
Re: Twin outboards on tender

A single 6 will outperform twin 3s in terms of speed but not "pushing " power. Twin 3's will allow for a heavier or loaded dingy to move faster in a current for example. But will be a pain to try and drive and turn the tiller handles and accelerators
MikeFergie is offline   Reply With Quote
Old 08-02-2017, 23:16   #4
Registered User
 
markpierce's Avatar

Join Date: Aug 2010
Location: Central California
Boat: M/V Carquinez Coot
Posts: 3,642
Re: Twin outboards on tender

Surely, two 3-horsepower engines will be much heavier than a six. Will the dinghy handle the extra weight? and how does one maneuver with two outboards without a sophisticated system?
__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 09-02-2017, 00:48   #5
Registered User

Join Date: Dec 2014
Posts: 163
Re: Twin outboards on tender

Yes 2 threes will be heavier, but we take them off and lift them onto the transom mount before hauling the tender on deck for passage. Its the handling of the outboards up onto deck that's deterred me from getting a heavier one.
Steering could be a simple pipe connection between the two steering handles perhaps.
Getting up onto plane is the gain I'd hope for, top speed isn't a big deal provided planing can be maintained.
Maybe its foolish thinking, but I'd like to hear from anyone who's tried this.
nzmal is offline   Reply With Quote
Old 09-02-2017, 01:55   #6
Moderator
 
Pete7's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 12,124
Images: 14
Re: Twin outboards on tender

With larger boats you loose about 1/4 of the power due to the increase drag of the gear case and prop losses etc. So 2 x 40hp outboards equal a 60hp single. A single 75hp outboard will out perform 2 x 40hp both in acceleration carrying capacity and top speed. I bought the 75hp engine version of a rib and the dive club the 2 x 40hp version, a decision they quickly regretted.

In addition to connecting what are you going to do about the throttles? if they are the sliding lever type that might work.

Do you have the gearbox model with neutral and forward, that would make life a lot easier controlling the tender as you could start with one engine then engage the other once moving. How about borrowing another small outboard and trying it first before buying anything. Be interested to hear the results, however, even 6hp on a 10ft rib isn't going to do much other than lift the bow and burn petrol.

Pete
Pete7 is offline   Reply With Quote
Old 09-02-2017, 06:30   #7
Registered User

Join Date: Aug 2014
Location: Astoria, NY
Boat: Sabre 38
Posts: 563
Re: Twin outboards on tender

Check out the likes of a Suzuki DF6. Only 55 pounds. Maybe 50% additional weight for twice the power? Not a bad compromise.
__________________
Stephen

s/v Carpe Ventum
1983 Sabre 38
My Intro
fallingeggs is offline   Reply With Quote
Old 09-02-2017, 07:35   #8
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 26,879
Re: Twin outboards on tender

Be a conversation starter, but would also be twice the maintenance
a64pilot is offline   Reply With Quote
Old 09-02-2017, 08:25   #9
Registered User
 
siamese's Avatar

Join Date: Dec 2008
Posts: 196
Re: Twin outboards on tender

When I was 13 or so, I had an Evinrude 3 horse on my 12' aluminum boat. Under no condition would the boat get on a plane. My friend had a Johnson 3 horse but no boat, so we did the logical thing and mounted them both on my transom.

It was great. The boat readily went up on plane with both of us aboard, and we regularly operated the boat as a twin. Equivalent of a 6 horse? We never had the opportunity to directly compare, but having owned a 12' boat with a 6 horse as an adult later on, I'd say it was very close.

Neither motor had a tiller mounted throttle, which I suppose is still common on engines of this size (our engines were made in the 50's).

We took care not to rotate the engines so the props would meet, but that meant that operating the boat required a hand on each engine. It was fifty years ago, but I recall that we could cruise in a straight line holding just one engine, and could make small course corrections by turning just one engine. Otherwise, turns required a little coordination, but was not difficult.

Neither engine had reverse, but by spinning just one engine around we could go backward.

For a couple of boys who desperately wanted a planing boat, the twin engine setup was great. For an adult with the means to acquire a 6 horse, I think it'd be a bad idea to have twin 3's. Too cumbersome. Executing a sharp turn with a 6 horse means turning the engine while twisting the tiller mounted throttle. Easy. With a twin setup, you're using both hands to make the turn, so there's no practical way to operate two, cowl mounted throttles. That's just one example.

Also, each of our two engines was a twin cylinder, so they ran much smoother than today's single cylinder 3's. On a plane, with the engine's rpm synchronized, it was a very smooth power package. I would think two singles would be more of a rattling cacophony. By the way, I think it's a rotten shame that they no longer make any small twin cylinder engines. The old twins were much nicer to operate. We used to travel as far as Grand Rapids to Grand Haven on the Grand River in West Michigan. Check that on your chart! I remember occasionally snapping a shear pin where the river was unmarked. We'd pull up on shore and use pliers to break off a piece of wire fencing to act as a shear pin and be on our way. I doubt a modern 3 horse would withstand the way we used our old motors. I sold that 1956 Evinrude (still working) in 2013.

Linking the two motors together for easier steering would probably be more trouble than it's worth.

I would greatly prefer a single 6 horse, and compensate for the additional weight with proper lifting equipment. If I was planning to regularly operate my dinghy, I would definitely get a twin-cylinder, even if it meant going to an 8 horse (I don't know offhand whether a 6 is currently available as a twin).
siamese is offline   Reply With Quote
Old 09-02-2017, 08:49   #10
Registered User

Join Date: Jan 2017
Posts: 495
Re: Twin outboards on tender

Quote:
Originally Posted by nzmal View Post
My rib 10' has a 3hp merc and ticks along ok.... but more power is often thought wanting.
Trouble is I don't want to go heavier outboard for lifting and stowing so I was thinking... twin 3hp mercs?
Anyone tried this approach?
In my experience, a second outboard gives more power but not more speed. If you are pulling a barge or a large boat, the second outboard gives power.
A second same-hp outboard will probably give no noticeable increase in speed for your RIB. You will be FAR better off getting an 8 or 9.8 hp for those longer trips when you want to plane and speed along like the RIB was made to do.
But a second 3hp will not do what you need.
I had twin 50s on a Boston Whaler. It was the fastest boat around, but the second engine did not give a great increase in speed; only a moderate increase. I talked to MANY fishermen in Alaska. They all have a large engine and a spare much smaller OB that is mostly unused that will bring them home if their engine fails. They do not use twin same-size engines because it gives almost no benefit.
I must highly recommend a 6 or 8hp for what you want.

I use a little electric trolling motor for very short stuff. It's quiet. Even quieter than a Merc! But not speedy. I use a 9.8 or a 15 on my 10' RIB for most runs.

I also used to run a 15hp and an 18hp on a 15hp open boat for fishing. I needed to steer and run with both tillers but it was no impossible and I managed without mishap. The additional 18hp did give me somewhat more speed to get to the fishing area. I would have been better-served with a single 25hp.
KP44 is offline   Reply With Quote
Old 09-02-2017, 08:58   #11
Senior Cruiser
 
seasick's Avatar

Cruisers Forum Supporter

Join Date: Sep 2007
Location: Bend, OR
Boat: Brewer designed Pacific 43 in fiberglass. Center cockpit set up for long-distance single handing.
Posts: 472
Re: Twin outboards on tender

We sailed side by side through the South Pacific with my brother and his wife in the 80s. We both had Yamaha 2 horses for our separate skiffs. On occasion when we had a long ways to go for an emergency beer run, we would put both outboards on my fiberglass, lapstrak eight footer. It was easy to handle and really scooted along. Muerelle Bay to Niafu six miles with the confidence born of redundancy. This practice was more of a novelty than an everyday practice but we found it worked well.
seasick is offline   Reply With Quote
Old 09-02-2017, 10:27   #12
Registered User

Join Date: Oct 2015
Location: Summerstown Ontario Canada
Posts: 315
Re: Twin outboards on tender

Quote:
Originally Posted by nzmal View Post
My rib 10' has a 3hp merc and ticks along ok.... but more power is often thought wanting.
Trouble is I don't want to go heavier outboard for lifting and stowing so I was thinking... twin 3hp mercs?
Anyone tried this approach?
Any reason why it may be a bad idea?
Would it provide similar performance to a single 6hp?
We ran twin 90s on a rescue boat and I always wondered what a 150hp would do and we did try it. The 90s were great for towing and manoeuvring when entering harbours of playing around marinas. The 150 was great for speed and quick response and much less maintenance. It would tow good however we never ran it long enough to know the wear and tear of it. We then moved on to a Limestone 24' with twin Optimax 150. They were good for take off, top speed low speed for towing and economical. They were all Mercury and ran forever.
seabreez is offline   Reply With Quote
Old 09-02-2017, 10:51   #13
Registered User
 
Cadence's Avatar

Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 7,884
Re: Twin outboards on tender

Quote:
Originally Posted by nzmal View Post
My rib 10' has a 3hp merc and ticks along ok.... but more power is often thought wanting.
Trouble is I don't want to go heavier outboard for lifting and stowing so I was thinking... twin 3hp mercs?
Anyone tried this approach?
Any reason why it may be a bad idea?
Would it provide similar performance to a single 6hp?
Get a six. If you can get a two stroke.
Cadence is offline   Reply With Quote
Old 09-02-2017, 11:12   #14
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 21,658
Re: Twin outboards on tender

I don't think two 3's will plane the 10 ft RIB, so it will go just as fast with one 3. Yeah, you may have a bit more power below planning speed, but also carrying more weight.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 09-02-2017, 11:15   #15
Registered User

Join Date: Dec 2016
Posts: 743
Re: Twin outboards on tender

My friend's family has a small boat with twin outboards. The story is that Grandad was an old tugboat captain, and was just used to driving that way.
__________________

toddster8 is offline   Reply With Quote
Reply

Tags
outboard, tender

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
For Sale: 1996 Gemini 105M w/ Twin 2009 Yamaha Outboards delmitch2 Classifieds Archive 0 04-04-2010 16:19
Florida Keys Boat Rental - Single or Twin Outboards? marty9876 Powered Boats 7 10-12-2009 13:52
Center board vs keel vs twin keel vs twin centerboard jscott Monohull Sailboats 32 26-03-2009 14:48

Advertise Here


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 16:52.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×

ShowCase vBulletin Plugins by Drive Thru Online, Inc.