Twin screws

Posts about mechanical systems on a Telstar, including the outboard engine.

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Twin screws

Postby Mangodoc » Sat Jul 15, 2017 9:45 pm

Anybody else got twin motors? I'm equipped with twin Mercury 25hp (not counter-rotating, but at this hp I doubt it matters). Only the port motor is linked with the tiller, but there are still several advantages:

1. Department of Redundancy Department
2. Maneuverability in tight quarters or if rudder fails
3. Small enough to manual start easily
4. Light enough to pull out by hand and maintain

The PO stacked the second throttle on the original, and they stick out a bit into the cockpit, but it's not a problem. I'm sure I'm carrying a little more weight aft which may affect my weight distribution, especially for trailering (see my recent post about trailer woes), but Mercury lists these motors at 174lbs each, and I doubt a single 50hp weighs much less. One concern I do have is that my motoring speed doesn't seem very fast, maybe 7-8 knots at 3/4 throttle, and PCI lists a 9 knot speed with a single 20hp.

Anybody else have experience with twin screws on a Telstar?
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Re: Twin screws

Postby escape » Sun Jul 16, 2017 4:51 am

I thought of adding a second motor for the control it provides. But I don’t want to put more weight aft. I have a 20 hp Tohatsu and the max speed is about 6 to 7kn and I generally cruise at 5kn when the boat is fully loaded in vacation. I was a bit disappointed as I expected to do 7kn+. Same thing under sail, much less than advertise, still it is a comfortable and quite fast boat to sail (faster than a 28' mono).

I would like to see a picture of how the 2nd motor is mounted.
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Re: Twin screws

Postby Mangodoc » Mon Jul 17, 2017 4:47 am

I'll shoot some pix when I go back down in a couple of weeks. Basically the PO had a well fabricated of aluminum that is almost identical to the port side and mounted the second motor on it, with the throttle stacked on the other as I said. I really like having the twins for the reasons I listed, although I'm not really sure having 50hp does much for me. I don't think this boat is going to break 10 knots under power without some radical lightening, and the compromises wouldn't be worth it in this boat. If I wanted to be that uncomfortable I'd be in a Corsair :lol:
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Re: Twin screws

Postby Mangodoc » Fri Aug 18, 2017 12:17 am

Here are pics of my twin engine setup:
IMG_0862.JPG
IMG_0862.JPG (31.57 KiB) Viewed 124 times
IMG_0860.JPG
IMG_0860.JPG (36.46 KiB) Viewed 124 times
IMG_0861.JPG
IMG_0861.JPG (25.91 KiB) Viewed 124 times
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Re: Twin screws

Postby Ron » Fri Aug 18, 2017 11:42 pm

350 pounds (174 x 2) mounted in the stern of the boat? Post a picture of the boat in the water. I'm curious which way the bow is pointed.

I can do 7+ knots with my single, 125 pound Honda 20. Around 6 at 2000 to 2100 rpm. I'm using a 13 inch high torque prop with a 6.5 pitch. Any higher pitch won't work that well on a sailboat with a top end of maybe 8 knots. A 50 hp would need something else.
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Re: Twin screws

Postby Mangodoc » Sat Aug 19, 2017 1:58 am

The bow is pointing North...
IMG_0674.JPG
IMG_0674.JPG (40.63 KiB) Viewed 118 times

But seriously, she sits pretty level in the water.
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