Twin vs Single the true answer

Screaming04 · 18 August 2010, 00:58

I've got the final answer to the eternal twin versus single debate.

I prefer both. :o)

30 kt cruise on the single !!

(sorry for the bad pic... I was looking forward and taking the pic astern at the same time )

BogMonster · 18 August 2010, 01:57

Developing the theme ... you could fit three engines, with the centre one propped to use as a single and the outer two propped to use as twins

There was an Etec promo video doing something similar that I saw a while back, the Etec would plane happily on one engine at a fair old speed while whichever lardy four-stroke was being tested (forget which one) couldn't get on the plane and was chugging along at about 8 or 9 knots

Screaming04 · 18 August 2010, 04:12

This would be the video...

http://www.youtube.com/watch?v=7hKoQCkRryc

I was inspired to try the single because of a picture I saw at Polaris years ago... At the time I had never considered that a twin engined boat would be able to operate on plane using one engine.

This is my boat's new "green mode".

Bigmuz7 · 18 August 2010, 07:38

Quote:

Originally Posted by Screaming04

This would be the video...

http://www.youtube.com/watch?v=7hKoQCkRryc

Kinda hard to argue with that vid .. unless he got his key float stuck under the throttle off the Yam ofcourse

Screaming04 · 18 August 2010, 12:09

Quote:

Originally Posted by Bigmuz7

Kinda hard to argue with that vid .. unless he got his key float stuck under the throttle off the Yam ofcourse

I just wish that they had mentioned the prop pitch on the yamaha.

Roy Smith · 19 August 2010, 14:11

I bet in real life with an independant tester
the result would not be so one sided, its easy to rig this type of test,
same as cars put bad cheep tyres on a fast car then swap to say P Zeros
and look at the differance, having owned both Etec and Yamaha i know which i would want.

BogMonster · 19 August 2010, 16:20

Quote:

Originally Posted by Roy Smith

I bet in real life with an independant tester
the result would not be so one sided, its easy to rig this type of test,
same as cars put bad cheep tyres on a fast car then swap to say P Zeros
and look at the differance, having owned both Etec and Yamaha i know which i would want.

true enough but in that case you would expect a similar set of videos from diehard 4 strokers with Yamahonzukis sinking Etecs...?

TBH I don't see the point of twins if the boat (whatever type) is unable to plane on one engine, as if you can only do 8 or 9 knots you're only a few knots better off than a single man puttering home on his aux ... unless you carry a spare set of fine pitch props and can change them over to get you moving, it's still going to be a long trawl home.

Straw poll, 'cos now I am curious, of all those on here with twin setups, who can plane on one engine and who can't?

GordyP · 19 August 2010, 16:36

Mine can, will do 35kts on one at full tilt and will cruise comfortably at about 25kts. I agree that if you are better being able to do a useful speed on just the one.

Screaming04 · 19 August 2010, 16:58

Quote:

Originally Posted by BogMonster

TBH I don't see the point of twins if the boat (whatever type) is unable to plane on one engine, as if you can only do 8 or 9 knots you're only a few knots better off than a single man puttering home on his aux

Although perhaps not common in the UK, over here, there are plenty of heavy outboard powered boats that need 500 hp or more. Since no 500 hp outboards are made, they require twins but would never be able to plane on a single.

I do agree though, on any "normal" boat, twins are pointless if you can't plane on one.

I too am curious as to those in smaller boats operating twin 40's or 60's. Can they plane on one?

GordyP · 19 August 2010, 17:13

Used to drive a 5.4 SR with twin 40's, it would plane on one engine but only if very lightly loaded.

willk · 19 August 2010, 17:24

Quote:

Originally Posted by Screaming04

I too am curious as to those in smaller boats operating twin 40's or 60's. Can they plane on one?

Meh 6.5 with 90s can plane quite happily at 22.5kts on one wing

She falls off the plane at about 16kts

BTW, Nice rib you have there lad

Screaming04 · 19 August 2010, 18:01

Quote:

Originally Posted by willk

BTW, Nice rib you have there lad

Thanks! I just can't stop putting up pictures since I've figured out how.

yorfuoj · 21 August 2010, 14:48

I have another answer, but on a very uncommon rib !

The rib is a Stingray-Tomcat (european name) 6.3 catamaran, with 2x50hp Tohatsu (carb version) and a pair of (too) long props (15" stainless for speed)

With 6 male adults on board, she was unable to plane on the starboard engine - but she did on the port one.
The top speed was 36knots with 2 on board, not bad at all.

The same boat run at 45 knots with a pair of 90 Yam (2 stroke) and 15" ali props @6000 rpm, a bit too high - 16 or 17" SS should gain 2 or 3 knots easily, possibly more.

9D280 · 23 August 2010, 11:02

And from the very dim & distant past, SR5.4, twin Yam premix 30s. - Just planed & no more, but took forever to get rid of the ballast!

Pikey Dave · 05 September 2010, 22:11

I can plane quite happily at 28kn on one engine, using both engines gets me about another 10kn. I'm on 19p Mercury Rev4s, it was always the plan to be able to run on one engine.

eilean mor · 05 September 2010, 22:25

I used a SR 5.4 with twin 30's and it would plane on one, - with just the driver, or with one moveable crew as well, to get it over the hump, but no more than that.