Twin engines.

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

Moderators: a j r, TDockside, Miles, Moderators

Post Reply
Dan Wolf
Posts: 98
Joined: Mon Nov 03, 2008 5:15 pm
Location: Naperville, Illinois

Twin engines.

Post by Dan Wolf »

I currently have a 40hp Johnson Seahorse on my 61 Sea Coaster. I can get my boat out of the water ok with 2 adults. With a little tilt adjustment, and everyone leaning forward I can get 4 adults up. My top speed is 23 mph. Anyway I am kicking around the idea of putting another 40 Johnson on the back. I like the idea of double engines. But, how do the throttles work? Do I need two throttle controls or does one work both engines. Second, how do they connect to work in conjuntion with each other.
I'm not sure if this is a good idea either, do you think there would be too much weight in the back? Could I put too much strain on the transom. Should I get a bigger boat?!! Looking for input. Thanks...Dan
LancerBoy
Posts: 1417
Joined: Mon Jan 28, 2008 3:47 am
Location: Minneapolis

Post by LancerBoy »

OMC has dual controls for twin installations for Johnson and Evinrude. There is a middle insert between the two halves of a regular control box. You end up with two throttles and two shift levers.

The motors are connected with a rod with turnbuckle. If you have cable and pully steering, you just shorten the cables at the motor. Nothing special is required.

I have pictures of my twins and the components. I'll have to dig to get 'em posted. May be awhile.

The Peshtigo Sea Coaster for 1961 was rated for up to 75 HP. Twin 40s will get you 80 HP. I would not worry about the extra 5 HP. The weight may be an issue.

Twins will give you more thrust and more out of the hole power vs. a sinlge of the same combined HP. You will be surprised how fast you get up on plane. The top end will not be as much as a single of comparable HP.

A 1961 Johnson or Evinrude 75 HP outboard will be plenty powerful for your 15'-10" Sea Coaster. This may be a viable option.

With twins, just keep in mind you have two of everything. And they can be twice the headache of one motor! I should know! I had to be towed in twice last summer and that's plenty embarrising when I had two motors and neither worked!

However, they look cool and the sound of the two humming in unison is music to my ears!

Andreas
john
Posts: 261
Joined: Tue Dec 27, 2005 7:33 pm
Location: Crosby (Houston) Texas
Contact:

Post by john »

What pitch is your prop, I have a 1960 Cruiser 202 16', with a 40 Evinrude, never a problem planing, top with 4 people is 23? Total pasenger weight about 750, top speed with myself about 25, and about 28 with 14 pitch, normaly run 12" pitch.

I have back to back seats which keeps weight foward, does your have rear seating, what trim pin are you using.

Weight of 40 hp is 140# x 2 = 280. Weight of 75 is about 240 so should not be a problem.

I also have a 1960 75 which I run once in a while.

My 40 gets 21 tp 30 miles per 6 gal tank, 75 gets 10 to 18, big difference.

You should be good with 49hp.
LancerBoy
Posts: 1417
Joined: Mon Jan 28, 2008 3:47 am
Location: Minneapolis

Post by LancerBoy »

Here is a photo of the twins, 1957 Johnson 35 HP. For the life of me, I cannot find photos of the control box (I have 'em someplace):
Image

Andreas
Post Reply