dual outboard motors

chewybug1

Recruit
Joined
May 26, 2009
Messages
2
does anybody have any info about having two outboard motors. I have a 85 16foot larson boat with a 60hp johnson outboard, well i picked up and identical outboard motor and i want to mount both on myboat, the original manual for the boat i have talks very little about the dual motors but it does seem like the boat can have them. so anyway any help would be great thanks
 

TexMojo

Seaman
Joined
Oct 30, 2009
Messages
62
Re: dual outboard motors

To me, having twins on the back of a 16 foot would look odd, but hey, go for it. I would sell both and upgrade to one big motor if it was me.
 

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,385
Re: dual outboard motors

Does the manual for your boat tell you the max HP you can put on it ??
2 X 60hp will be heavier than 1 X 120hp motor and will give lesser performance than a single 120hp.
However if the manufacturer states in your manual that you can do it then go for it.
I am assuming that both motors rotate the same way as well ???
Have you considered the controls yet ??
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: dual outboard motors

I used to see a small Hydrodyne with twin two-cylinder 50 Johnsons on it. Ran pretty well as I recall. The biggest thing you will need to check will be the side to side engine clearance and the narrow profile of the 60 should work out ok. Also, when you mount the engines the the right and left of the boat centerline, that will affect the mounting position (height)on the transom. Most transoms are made for one engine- in the center. You may have to raise each so that they cut through the water at the right height. Unlikely that the 60 comes in a counter-rotation model, so you will have some big time torque steer to wrestle with unless you go with a hydraulic steering. An interesting project. Good luck.
 

tmcalavy

Rear Admiral
Joined
Aug 29, 2001
Messages
4,005
Re: dual outboard motors

It's do-able and a lot of fun...especially with the older iron. I run two late 50's OMC Big Twin 35 hp's on a 15-foot early 60's tinny runabout. Had to move the gas tank forward to balance the boat...shorter boats get stern heavy when running twins, batteries, fuel tanks etc. back there. It's fun, but more work. Plan to pull the twins next spring and put an 64 Evinrude V4 60 hp on there and compare performance. Should save me almost 30 pounds on the transom. Might try to find a boat almost the same length as yours with twins and see if you can wrangle a ride/drive...to see if you like it well enough to do it.
 

jay_merrill

Vice Admiral
Joined
Dec 5, 2007
Messages
5,653
Re: dual outboard motors

I have had a twin installation and like them. That said, unless the boat is so big that it requires more horsepower than is currently available in a single engine, the negatives generally outweigh the positives. Most of the negatives relate to cost and performance. The simple fact of the matter is that twin installations are not as efficient as a single installation of the same horsepower.

You will carry more weight on the stern and burn more fuel, than you would with a single 120 hp engine. You'll also add the compexity of an extra battery, control unit, tach, fuel tank (unless you have one, large one now), fuel lines, etc. You will also have to change your steering system to accomodate a pair of engines, rather than a single engine.

Another thing that you will have to do, is to select the right pitch props for the new installation. You need to go to a higher pitch than what you have on the single engine now, but not so high that you can't plane the boat if one engine fails.

While your boat will go much faster than it does now, it will be slower than if you upgraded to a single, 120 hp engine, with the drag associated with two lower units being the main culprit. Your operating and maintenance costs will also be higher with the twin installation.

I would also plan on the possibility of having some problems related to torque steer and lean.

On the positive side, you will enjoy a certain amount of security that you don't get in a single engine. As long as you don't lose power in both engines due to fuel contamination, a log in the water, etc., its rare to have both engines fail at the same time. Increased maneuverability at the dock/trailer is also nice. If you ever do any towing and need to put the boat in a side tow for any reason, you will especially appreciate the ability to control the tow at low speeds, if you have two engines.

All in all, I would just evaluate the wisdom of the setup in terms of whether or not the boat will perform as it was designed and whether or not you can accept a higher cost associated with the twins.



???
 

Bifflefan

Commander
Joined
May 27, 2009
Messages
2,933
Re: dual outboard motors

I way if you want to do it, DO IT.
I think they look cool. And its something that not everyone has. As far as the worse fuel economy, who cares. Its COOL!!!!:cool:
 

TN-25

Chief Petty Officer
Joined
May 27, 2008
Messages
607
Re: dual outboard motors

Here's a picture of a Mirror Craft Ski n Troll 16 that I modified from the brochure picture. In the brochure it had a single 65 horse, but I thought that was boring. Since the boat is rated for 80 horses I decided to throw dual 40s on the back. After I did it I realized they were 25s, not 40s. The look would be very similar anyway.
 

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