Twin Engines

Suggestions, concerns, and what is the correct power plant for your Thompson.

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Twin Engines

Postby Barry » Sat Jan 21, 2012 7:50 am

I have a 63 Sea Coaster with the original 40 Johnson. I have a chance to buy an identical motor in excellent condition and I was pondering the idea of setting up a twin configuration. The transom is like new but I'm not sure if it's designed to handle the extra load and torque. Any insights would be helpful. Thanks. :?:
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Postby Torchie » Sat Jan 21, 2012 10:37 am

Does your boat have a tag with a HP rating on it?
First check for that.
My 57 Off Shore has twin 35 hp Johnsons on it. They weigh in at about 150lbs a piece. Weights for your motor are available on line. Just google it and something will come up that will give you an idea abought the weight factor.

As far as torque goes I don't real know how that would affect the boats drivability. Would most likely get it up on plane faster though :lol:
Lets see what anyone else has to say.
Karl
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Postby LancerBoy » Sun Jan 22, 2012 3:27 am

Look at the brochures from the early 1960s. See how many of the boats are pictured had twin motors installed. I have a 1957 Thompson of Peshtigo 16'-7" Sea Lancer with twin 1957 Johnson 35 HP motors.

No problem.

Andreas
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Postby Bill Dunn » Sun Jan 22, 2012 2:07 pm

I would check the H.P. rating for the Sea Coaster. I have a '59 Sea Lancer and it is rated for up to 90 H.P. As long as you are in that ball park and the boat is sound, I agree with Andreas. I think the reason for running a lot of twins back then was larger H.P. motors were few and far between and were not as time tested and reliable at that time. Until the early 60's you had motors like the Merc dockbusters that were more challenging to use and keep running correctly and the big O.M.C.'s that weighed as much as the boats.

Bill
All Dunn ll
'59 Sea Lancer
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Postby Barry » Fri Jan 27, 2012 7:44 am

Thanks all for the help. I appreciate it and will likely go ahead with the plan. I'll let you know how it works out.
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Postby vernonfarmer » Mon Jun 25, 2012 6:49 pm

Somewhere I heard (read?) that twin outboards need to turn the props in opposite directions. Is this true or did I make this up in a bourbon induced haze?
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Postby Phill Blank » Tue Jun 26, 2012 3:23 am

Vernonfarmer,

It was not a bourbon induced haze. I do recall years ago, I'm talking back in the 50's and 60's, Eveinrude and Johnson did sell motors with opposite prop rotations for twin engine applications. I am sure the other manufacturer's did also.
The reason for this was to eleminate "prop walk". Prop walk is when two motors with the same rotation are on a boat they will tend to pull the stern in one direct or the other depnding on their rotoation of the props.
I am not sure if this is still done or not.

Phill
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Postby vernonfarmer » Tue Jun 26, 2012 3:42 am

Thanks, Phill...that's one thing I can't blame on the bourbon!

My sister in law has just purchased a 16' Yellow Jacket. She thinks it would look really cool with twin 35's on it. Finding one nice vintage motor is one thing. But two....and one that spins in the opposite direction, yet....sounds like a tall order!
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Postby Barry » Tue Jun 26, 2012 6:57 am

vernonfarmer wrote:Thanks, Phill...that's one thing I can't blame on the bourbon!

My sister in law has just purchased a 16' Yellow Jacket. She thinks it would look really cool with twin 35's on it. Finding one nice vintage motor is one thing. But two....and one that spins in the opposite direction, yet....sounds like a tall order!


Very tall! I have looked for more than 5 months now and finding a reverse drive seems to be impossible or maybe I'm just looking in all the wrong places.
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Postby LancerBoy » Tue Jun 26, 2012 10:19 am

On the smaller HP motors, say 40 HP and less, opposite rotation is not necessary. Not enuff torque, etc... to cause any problems if both turn the same way. My both turn the same direction on the '57 Sea Lancer, and it was never an issue.

They are so close together on one of these outboard boats I don't think it's a big deal.

Andreas
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Postby vernonfarmer » Tue Jun 26, 2012 3:41 pm

Excellent! Now where do I find motors as nice as yours, Andreas!
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Postby LancerBoy » Fri Jun 29, 2012 8:01 am

Have 'em built

Andreas
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Re: Twin Engines

Postby Threesheets » Sat Nov 09, 2013 11:01 pm

If you have any prop walk, you'll probably only notice it backing. It's common on large inboard twins to have counter rotating props, but on a small boat it can useful when docking if it's significant, especially an inboard. I haven't driven an outboard in a while and it occurs to me that being able to turn the engine into the turn achieves the same goal and much more efficiently.

Mike
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