Twins on a monohull ?

[Scott79]

Purely out of curiosity, ocassionally I have seen twin outboards on monohulls (6 odd metres) just wondering how it affects the boats performance, good, bad or indifferent?

Forget about the reliability/safety aspect, slower trolling speed using one, 2 outboards to service etc etc, really just curious on how they behave.

Thanks,
Scott.

[tigermullet]

Really well until one engine stops.

We had a rig with twins on it but I'd never do it again even though it performed brilliantly. We didn't mind the extra maintenance but having one engine stop (electrical fault) in the middle of Moreton Bay made us realise how lucky we were that it was dead calm or we weren't outside. The props were 19inch pitch - losing one motor saw our speed drop back to less than 6 knots so I think the safety angle is a bit of a furphy.

[Ally Jack]

Scott,

I have a Seafarer Vagabond with twin 115 evinrude ficht motor's.
My observations are they accelarate faster but slower top end to a single of similar hp on similar boat, fuel usage is similar, trimming the boat was harder when I first got it but I've got used to it now so similar, turning can be tighter if you throttle the engines accordingly, you can turn in your own length if you want to (handy at the ramp sometimes)

My thoughts
Ally Jack

[Chimo]

I have a Vag like Jack with 2 115 Evinrude Ocean Pros

What he said and top speed is only low 40Kn s so single is really a little quicker.

Operating is made easier with foils on the motors and trim tabs.

It will plane on one motor if the water is choppy to help get the boat up, not so easy on flat water though.

I like having a spare motor. Uses less fuel as you can turn one off when travelling slow.

Cheers
Chimo

[cormorant]

On a very deep v you can mount them either side of the v and not need 30 inch shafts

Out of the hole they can be brilliant in bar work as they have so much prop area and grip on the water

Great not to worry about trim tabs

If serious aout safety you need them set up completely independently , electrical fuel filters etc.

Maintainance is more expensive.

Some combinations can be lighter for more HP on the transom.

Trolling is cheap.

In some cases on older hulls the new huge colwed 4 strokes just won't fit bt the smaller twins will.

Can have a lower center of gravity at stern, with 2 props and cav plates in the water it acts as a great swell shock absorber at rest slowing heel and pitch.

Planing on one motor - we could do it. Make sure your steering connections have the ability to have one motor trimmed well up or even tilted with the other one normall even if you don't get full steering control ( ie straight blast to home) Tilting the seconfd motor makes a huge difference. We used to carry a prop spanner and spare lower pitch older props as we had counter rotating. That way if we were well out we would consider pulling the dead motor prop off and if fully ( or overloaded) loaded we would change to teh lower pitch so motor wouldn't labour and be overloaded. We always rn slightly underpitched to start with as load carrying was more important than speed so lightly loaded we had no issue planing on one at slow cruise.

Counterratating can actually add to the output and a clean wake compared to non counter rotating. No prop walk , straighter course, less autopilot corrections.,no boat heel less presure on steering cable / hydraulics.

Able to mount slightly higher than a single with some props..

[Chimo]

[quote=cormorant;

Able to mount slightly higher than a single with some props..[/quote]

Like Rakers on Evinrudes tho they possibly fit others too?

Chimo

[dodgyone]

Really well until one engine stops.

We had a rig with twins on it but I'd never do it again even though it performed brilliantly. We didn't mind the extra maintenance but having one engine stop (electrical fault) in the middle of Moreton Bay made us realise how lucky we were that it was dead calm or we weren't outside. The props were 19inch pitch - losing one motor saw our speed drop back to less than 6 knots so I think the safety angle is a bit of a furphy.


Used to do some offshore runs up to 150 km each way. Ran twins. Would still rather coming home on one than bobbing around with none.

[hakuna]

I have got twin 115 sukes on 6.8 plate. Would never have a mono again. boat better ballanced, use the motors as trim tabs even though I have trim tabs, not needed.
Better in white water work
less depth of water required to float the boat and best of all
THe hum sound great

cheers

[cormorant]

Does make me wonder sometimes.

Regardless of how good and reliable you think yor motor is you are a bloody fool if you don't have an auxillary. Frankly I am sick of towing single engine rigs in

Go and buy a 9.9 -15 hp sail drive and put a proper trolling prop on it keep it maintained by using it when you are trolling. People who call for help who are further out than rowing distance or own a rig that is large enough to fit an Auxillary and don't should be told to bloody get one not risk others in coming to collect them.

When you read the rules it says you must have a alternate power source and for years that has meant a paddle. Fair enough on a 10 footer but not on a 22 foot plate boat travelling as a individual not in a group.

Yep we have refused to tow people back in as they have gone out as a pair of boats and then after a breakdown moved a couple of people to the second boat and then called for a tow but left their mates to fish . Took us a while to catch on but they were abusing our trust and good nature.


If you can't be independent ( even by travelling as pairs with enough capacity to put all passengers in one boat for self rescue) when you are out offshore or in large bays - and that means 2 serperate forms of effective propulsion you are a idiot.- should be against the law and may well be in the fine print. A 15hp correctly set up will keep a boat facing into the swell and will slowly push you home. It will charge a battery and keep a bilge pump and radio going.

Rescue, epirbs, coastal patrol VMR police should really be for propper emegencies not a breakdown service on the water ( or they should charge boats a huge annual fee for that not the current pittance)


With that said the benefit of twins is self rescue and even holding position into wind and swell so you don't get swamped.

People really need to think about what happens when things turn to Sh1t.

Epirb response is not instant
help isn't 5 minutes away
nothing is easy in a small boat when it is pitching around
a half full of water boat is a different beast
human nature, shock fear , bad decisions
fatigue
Your motors are one of your best pieces of safety equipment used first - having one that doesn't work is a nightamre when it turns to crap


Yep a log in the water can kill twins as well but if there is a decent separation you lower the odds and carrying a spare prop will help.

[Fido]

I have twins on a 6.2 metre Plate Boat. Would never go back to single rig of this size. Lots of low down grunt. Safety. Top end is what I consider similar to a single rig. Always go for the most HP with the lightest weight.

[tigermullet]

Used to do some offshore runs up to 150 km each way. Ran twins. Would still rather coming home on one than bobbing around with none.


That's a point - perhaps we were over propped. On a rough day we would never had got back across the bar. Maybe a sea anchor chucked out in front and riding in backwards might have been a possibility but would rather not put the exercise to the test.

All academic for me now - old age sees me confined to the Pin;D

[Scott79]

Some really interesting posts there guys, thanks to everyone for their feedback.

Scott.

[ozbee]

can see no point in twins of the same hp . they use more fuel and in my boat a patriot you need a extra 50 hp to match the single . point is one motor wont get you up and if is set up to do that your wasting a lot of fuel . i have a 20 hp electric long shank and pull start . with a thrust prop this give me a good push at half throttle and on my way home . advantage also if you have a electric problem you can charge or pull and head home.

your spare motor can also be used for a tinny in the creek also . keep the extra 20 grand in your pocket in outlay saved for the next repower .this is where it really hurts for duels and is the crunch time for many and they have to sell them .
if motors were in realistic prices example is you can buy the same motor and the rest of a car cheaper than a outboard motor we would all be running twins.

[Noelm]

some of what you said ozbee, just isn't so, a given amount of HP will use the same amount of fuel (and can even go either way) whether you have 1 200 or 2 100's, servicing can be deaer, but not twice as much, you may have (say) a V6 (or a V8) or two 4's the difference wil be 2 spark plugs to buy, and two lots of oil, but the single big motor can use a heap more than a smaller one, so that evens out a bit as well, top speed in the single will be higher, but torque of the twins will leave the single for dead, so a lower planing speed can be held (and reduce fuel use sometimes) it is not all black and white like a salesman will try to tell you (or the owner of a single and a useless auxilary) buy what you like, if you feel safer with twins, then so be it, make sure they are completely independant of each other, lots say a well maintained motor will be reliable, and so it will be, but a lot of breakdowns are not related to age or maintenance, a spun prop, and broken fuel line, lots of stuff can leave you drifting or in deep trouble.

[ozbee]

perfect example noel is my 680 patriot with a 250 and a 680 with twin 150

because of his extra leg drag even though we are 50 HP less we have the same top end. i am using about 10 to 15 percent less fuel in cruise. i have swapped over to a 300 and still use less fuel than the two 150 and faster by 5 knots. because Suzuki have a higher reduction and swing a bigger diameter prop the hold up in a slow sea is much the same .

he cant get up on one motor and i have done a prop change in a sea on my father inlaw formula with two black anchors on the back . done it once but never again it is one of the most dangerous thing to do in a sea.

you must note noel i am not advocating a single motor as i have a kicker set up properly on my vessel and it will push quite well .when you start adding water pumps etc your costs are a less.many people don't realise what a proper kicker can do . in old day lugger boats 30 feet long would cart sugar out to the ships many of them would have a 12 to 15 hp lister chugging along carry gods now how much weight. most people shove a short aux on an expect it to grab water well . unless it swings further down than the hull your wasting your time .

another point is Australian boat manufactures tend to have lower HP ratings than the yanks this very much restricts you in getting a combination of enough spare hp to get you up on one. if they allowed a lot of twin 150 rigs to go twin 200 you could get up on one and throttle back to ease some load

the money i saved in buying single minus the kicker was nearly enough in three years when the motor was about to come out of warranty to change over to a brand new donk with 7 years warranty. i will not rubbish big twins there great but there advantages are far less now with modern motors but there replacement and maintenance costs can be a killer.

i go 100 ks out to sea pretty regular and no way would i go totally single just in these expensive times i feel i have a cheaper and safer combination( by the ability to pull start as well and charge) that can see me out over a decade or more with out great outboard outlays.

advances on large outboards over twins

duel charging on a single no switching anything deep cycle being topped up all time as well as your crank

larger diameter props being swung but on smaller sharper skegs . result of motor drive offsets resulting in better fuel economy and torque.

fact the 300 etec is pulling far better fuel economy than the 250 at no mater what speed or conditions within the 250 capabilities.

fact my 300 zuk is pulling far better fuel economy than the 250 in the same conditions

why is this so because most of the engineering advances are in the high hp line of motors and has not filtered down as much in the mid range motors.

weight has been greatly reduced in the large donks now and many boats can run larger HP single motor than duels.

really it is about affordability and choiceand hopefully it will always stay that way resulting in safe boating for all.