Single or Twins

[skipalong]

hey guys this question has probably bee raised before but i was wanting to know what would be better, a single motor or two.

the motor of choice will be suzuki, i was wanting to run 2 x 115's , i went and saw the guy who is going to fit them today, and he said it would be a complete waste of time and money, my main purpose was for safety and to spread the weight on the arse of the boat.

i checked out prices and they wouldb relatively close in the end anyway,

if anyone could shed some light on it would be much appreciated guys

cheers justin.

[Quaker]

I'd prefer twins. If one dies you've got no problems getting back in.

[Roughasguts]

I would have a single, cheaper to run, maintain, and better performance.

[Blackened]

G'day

What kind of boat is the real question.

IMO, Twin screw setup is a waste of time on a mono UNLESS the fuel and electrical systems are completely seperate

Dave

[skipalong]

The boat is going to be a 6.8 riptide halfcab, was going to run 1 tank, but sealed into 2 sections 1 for each motor, so if water gets in the fuel

[Fido]

I run twin motors now.
Just one large fuel tank with a micro fuel filter is adequate. I have my boat set up so I can start on one or both motors and run the elctrics just off one battery if desired.
It's a big decison one motor or two.
My previous motor was a small block 200 hp etec. Faultless and economical.
I now run twin 80 Hp 4s Yamahas. Very economical and provide adequate to speed. 39.4 mph on a 6.2 plate boat.
One motor will plane the boat but should ideally be repropped. Somewhat impractical in outside conditions.
The benefit of twins is the backup of an extra motor and the torque out of the hole. Coming and going through bars its great.
I would get the biggest horsepower if the range all weighed the same.

[trueblue]

I would go twin motors if I was getting a new boat

Mick

[CB77]

At the end of the day it all depends on your bank account!

I wouldnt bother on a Mono hull.

Personally I wouldnt want the intial cost of the extra motor or the ongoing maintenance and fuel costs.

Not to mention one day if you keep the boat you will be up to replace 2 new engines.

If you are a charter operator or business that can write a lot of costs off it might be a different story.

The other thing is where are you going to use the boat, do you really need the security of the extra motor? The Coast Gaurd are very good these days, unless you are going to remote areas probably a big waste of money.

[backlash08]

Hi Skipalong,
I full understand your postion, I'm in the middle of having a newie built (plate mono, fisher)and had exactly the same question, spoke to many people as well as the boat builders that I was considering, the resounding feeling was 1 big one based on new engine reliabilty, cost, weight etc. For me, If engine does fail generally within range of coast guard and if not, would be with another boat anyway and I keep fuel systems clean....anyway good luck with the choice but for me it is only 1 and as big as practable
cheers - Craig

[Poodroo]

My uncle Frank OO would tell you to go twins for sure based on what has already been mentioned. Safety. If one motor fails the other one will get you home. He has the Cruisecraft 685 Outsider with Twin 115hp Yammies and it flies along nicely. Only downside with twins is it tends to double service costs etc but when going outside it is hard to put a price on safety.

Poodroo

[Noelm]

OK, here is the "good oil" on 2 V 1 Motor, given the same total HP like (say) 2X 100HP over 1X 200HP on the same Boat, the results will be, the single is faster, will use a tad less fuel (but not a lot) will be a bit cheaper to maintain, but also not as much as you think, because the smaller the Engine, the cheaper it is to service (up to a point) so you may have 6 plugs in the single, and only 8 in the twin, so it is not twice as much, now for the twin rig, it will be much more powerful, will be able to maintain a steady plane and cruise, will push a heavier load, will be easier to control around the ramp (after some practice), trolling is cheaper on one smaller Engine, the downfall is more weight, and cost, and indeed the two Motors need to be able to operate as two completely seperate systems, from Fuel to Batteries, safety is a small factor, but not too many well Serviced Motors give trouble these days, but it can happen, and not just from a straight out breakdown, lots of things can render a Motor useless, from a spun prop, to even rope caught around the Prop, there is a host of other small fores and against but I have owned both systems for years, fitted up both setups, repowered from one to the other, and that is the very basics of the differences.

[Noelm]

I forgot the biggest advantage of twins, there is just nothing that sounds as sweet as a pair of Outboards in sync at full noise!!! and they look just sooo cool!

[ffejsmada]

I'd prefer twins. If one dies you've got no problems getting back in.

Unless you have a fuel related problem and you're sucking out of the same tank, then you're rooted. You've got problems then!
Trust me, I've been there!!

Two motors, two fuel tanks, two fuel lines.

[Chimo]

I have two 115s and I like it that way for security and its a nice note as stated above.

When you dont need two you just turn one off, a lot like the new wizz bang car engines that shut down part of the motor when not needed. Yes a bit dearer than a single to buy and service but safer and cheaper than a tow.

Also on a mono if propped right you can get great economy and even on a heavy mono in rough water it will plane on one.

Plus even on a mono you can do circles in the same place with two motors

Cheers
Chimo

[Gagga08]

Single definately....unless your loaded and earn 500,000 grand a year in which case go with the twins!

[Alchemy]

I understand that you don't get the same performance from say 2 x 100hp versus 1 x 200hp, and that this is apparently due to the motors being close together and the associated turbulence leading to a percentage of cavitation? I guess this isn't such a problem on cats as the motors are so far apart. So, what if a mono was fitted with twins mounted on the outer edges the transom, would this be a viable set up? Reason I ask is that there is a boat for sale in Mackay set up this way.

Thanks,
Dave.

[Noelm]

it is more to do with drag on the lower unit, you have two in the water instead of one.

[Noelm]

OH and a problem with a mono with Motors right on the outside, is when you do a turn, one will be out of the Water becuase of the lean, they are usually mounted close together for this reason.

[wilcara]

If you are going a long way, I'd like twins. Re the horsepower I can't remember the formula but I know that 2x100 does not equal 200, more like 175 in a single. However twin systems would be nice. My mechanical ability is on a par with your average sheep dog and I hate sitting out in the sea by myself listening to the note of that solitary motor - did it just miss?

[ozbee]

do what what i did i had great problems making my mind up so i went like this

have the hull made set up for twins so you can go either way this will only make a better boat flotation wise anyhow . check out someone who has duels and see if it can lift up on one you will be surprised how many cant . this was the case with my patriot . if you cant get up and go put a small auxiliary motor on which is easier because you have a duel transom with a thrust prop. this will give you sailing speed and safety.

benefits you will save up to 20% in fuel costs every trip plus a a big saving for your next motor in a bout 5 years in that you saved a lot at the initial outlay by buying one and the fuel savings you can replace it brand new again instead of having to keep two old motors a lot longer.

one advantage by having a auxillary is that if you have battery problems by
pull starting option available still on motors up to 20 hp but also elctric start you can use them to up charge your battery enough to kick start the larger motor.

motors are so much more reliable now either way you go is fine but you may be uneasy for one motor like i am but if you cant get up and go on one you wont be much faster than the set up i have without running the risk of burning a hole in the piston of your good motor. this saying i will change the prop out there may sound alright but is quite dangerous to attempt in a sea if not down right impossible at times

[sempre]

I'm a little confused about everyone saying twins use more fuel .
I can tell you my 115 's use less fuel than the 200 .
Justin , 7.4 loa Riptides like a single 250 , or they work just fine with 115's , and i think you will get much better fuel figures out of the twins .
I'm not sure why the dealer told you it was a waste of time .

[skipalong]

hey fellas thanks for your imput to my situation, i have been told that i will get better fuel economy over boats of equal length with having two motors rather than one, i will be doing more than 5 months of the year trolling and the rest offshore, and was another reason for two motors and price differance was only around $6000, cost was never an option just after the best result for the boat and travel at the end of the day.

[skipalong]

yeah cheers sam my old man went and saw graham jeffers yesterday , we had a few problems with our suzi on the weekend, but while he was there, i got him to find out about the motors and he just said it would be pointless, i still am favouring the twins, but dont want to make the wrong decision.

cheers justin

[sempre]

Go two and you wont

[Noelm]

another thing that is handy with twins, is trouble shooting at home or when you are stuck away form a Service place, you will always have another working Motor for comparison to reapir the dead one, BUT be careful you do not end up with 2 dead ones with bad mechanical skills and rough workmanship.

[Dean1]

another thing that is handy with twins, is trouble shooting at home or when you are stuck away form a Service place, you will always have another working Motor for comparison to reapir the dead one, BUT be careful you do not end up with 2 dead ones with bad mechanical skills and rough workmanship. Yes good point Noelm, one of my 70's was getting hot at full revs, i swapped the thermostats to pin point the problem but it suprisingly fixed the problem! One must have required a touch more cooling than the other obviously. Twins look TUFF and better resale with twins, good peace of mind when out the shelf etc. Just another reason to buy a cat :P

[FNQCairns]

I think ozbee nailed it, just because it might just plane on one engine doesn't mean you can, you can come home at displacement speed though on one engine without fear of doing damage. So where is the advantage of twins after this? I cannot see any except from a rev head perspective -which appeals to me but not all people.

Funny enough many will say go twin so you have the spare engine if anything goes wrong but will also say why fit an auxiliary to a modern single engine boat, doesn't make sense, today IMO the average boat has less chance of coming home each trip under it's own single engine steam over the service life of the engine than than in days past.

My personal opinion is go single, fit an aux with remote throttle/gearchange hooked up to the now spare second dual throttle lever if you would like to troll with it often.

cheers fnq

[Noelm]

getting on the plane with one out of two Engines is possible, but not as easy as itsounds, the twins will be propped way too big for the single Engine to run as it should, if you are in a following Sea stiuation, sometimes you can get a "ride" and get you up and running, but for max safety for you and your Engine, just be prepared for a slower trip home, you will still get there, but it is a very long trip at 4 to 12 knots on one Engine from the shelf or somewhere like that, but still way better than sitting out there waiting for a mate to tow you home. Some Boats like cats are almost impossible to plane on one Engine, not too sure why, but it very hard to do it, regardless of the HP.

[Dean1]

getting on the plane with one out of two Engines is possible, but not as easy as itsounds, the twins will be propped way too big for the single Engine to run as it should, if you are in a following Sea stiuation, sometimes you can get a "ride" and get you up and running, but for max safety for you and your Engine, just be prepared for a slower trip home, you will still get there, but it is a very long trip at 4 to 12 knots on one Engine from the shelf or somewhere like that, but still way better than sitting out there waiting for a mate to tow you home. Some Boats like cats are almost impossible to plane on one Engine, not too sure why, but it very hard to do it, regardless of the HP. When one of my my 70's blew a stator out at the banks a few months back the most I could get out of one motor coming in was about 8 -9 kts running down a wave otherwise around 7 kts. 4 hour trip home but heaps better than an expensive tow. Should be right now with the new 60's but you just never know ;)

[backlash08]

Hey Dean, have you given those newies a run yet?
cheers - Craig

[Dean1]

Hey Dean, have you given those newies a run yet?
cheers - Craig Yeah Craig i sure have they are sweet!!!! They are VERY quiet and VERY smmmooootttthhhhh.... And they are punchier outa the hole than the 70 2 strokes! And fumeless and fuel efficient ;D And look hot and start straight away ;D Does this convince you im happy with em! Heading to the banks tommorow, they use 22 litres/hr for both at 22kts and will get a touch better once run in. I'll put pics and figures up once i work out how to download pics off new dig cam. Cheers mate.

[Noelm]

it is funny how Cats will almost never go well with one Engine huh? I reckon it must be something to do with it being right on one corner, and when you try to go, it wants to turn the Boat, so you need to steer oposite, which is sort of like going through a turn, which always "loads" up the Boat, I used to run a 23' with 275HP a side, and it would never go more than about 6 to 10 knots with 1 Engine, even with that HP, but you run with both, and it was fast/powerful I can tell you. Mind you way back, Markham Walers had some smaller Cats with 1 Engine on the side, they where never all that flash, but they did go.

[chop duster]

noelm,
are you saying they were rigged to run with only one engine on one side (sponson/hull)
never seen this before?

[Noelm]

yes, indeedy they were, they were about 4 metres long perhaps, some had a sort of side console thing some a bit different, but the Motor was on one side, Starboard from memory.

[skipalong]

yeah i at least you had two engines then, i dont really want an aux on the back,

[ozbee]

seems you have already got your mind made up go the way you feel just have a extra carton of beer in when the service bill comes also why do twin motor people feel they can not request a tow when single with a auxiliary doing not much slower can . remember most motor problems are fuel related so chances are you would be towed anyhow . if you got the cash to burn go twin there is a psychological chance you feel better out of it but be prepared when you get passed by a single motor of the same combined HP pisses all over you and uses 10 to 20 percent less fuel it can be deflating just race him at take off it will get some of that good feeling back.

there is one thing you need to consider which may not apply to you but i feel is very important and what are the circumstances you feel you will be in in 5 to ten years time. i have teenage children who love fishing so i see it more economical in that 5 years time in what i have saved in fuel costs and outlay i can probably buy the next new fangled motor be di fourstroke or gas or whatever in what i saved by going single.

if there is no one in your footsteps go the twins as you only live once happy boating.

[ifishcq1]

Both options are okay but after turning the family boat to a single we have found that twin 115 4st aren't in the ballpark of an easy run 250 one of the posts above that said different probably never did the exercise on the same boat

If you go wide with another boat or two they all help each other so there is no real safety gain with twins
and from experience a twin rigged boat just doesn't balance well with one motor in the air in any difficult seas

cats should be rigged 2up, trihulls are best single and monos single with trim tabs

cheers

SL