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Justin Rossiter
08-05-2013, 02:50 PM
Wanting to put an auxilary outboard on my 4.70 m cuddy cabin. Any ideas of what HP would be required to get me home in the event of mechanical/fuel problem. Have a 60HP yammy 2 stroke as the main engine.

Thanks

Swanie1975
08-05-2013, 04:05 PM
I used to have a 5hp four stroke on my 5.5m glass boat. I used it for,trolling and getting home twice with a max speed of 6-7knots flat out. Only sold it when I re powered the boat.

Cheers Ryan

stevej
10-05-2013, 10:04 AM
i just sold my 4.95 stacer with a 70hp small cuddy cab and bimini

i put a 9.8 tohatsu on there 26kg nothing comes close to the weight/hp of this engine
basic simple and started first pull every single time (i use to run it weekly or fortnightly when i started the main engine

with a high thrust prop it would push the boat at 6kph at half throttle.

with the standard prop it did the same 6kph at full throttle which would kill the engine pretty quickly if you ran it for extended periods of time

PixieAU
10-05-2013, 10:43 AM
aren't smaller motor better run at closer to full throttle with a heavy load?

Crocodile
10-05-2013, 09:21 PM
Hello Justin,
have big think about the whole auxiliary concept.
They are great for peace of mind but the realities don't stack up.
For:
peace of mind
Against:
1.weight
2.get in the way
3.being on one side lateral balance is affected
4.weight that far aft may cause the boat to squat
5.fuel supply, if your yammie is a self mixer, then the fuel has no oil, so you will need another tank for the spare motor or be able to add the correct amount of oil to the main's tank.
6.Four stroke spare motors make no sense at all, expensive, lack of torque and heavy.
7.unless the spare is a long shaft it will ventilate and the prop will simply churn unless you put it very deep in the water, which makes the controls hard to reach and risks drowning the motor
8.Two motors to maintain

Unless your main motor is dodgy or you are travelling in remote areas an auxiliary makes very little sense.

Use the money to join VMR, get a radio, maintain the main motor and treat it well.

stevej
10-05-2013, 09:49 PM
no standard prop will allow a motor to reach full revs when ued as a aux, it puts them under severe load that they are not designed for

you are never going to plane a boat with a aux so pitch the prop to reach full revs but back it off a bit, mainly for fuel economy for the hours it will take you to get back in

bf90
11-05-2013, 07:07 AM
I used to have a 5m glass half cab with a 70 johnno and a 8 rude as the back up. In the time I had the boat I had to use the little rude 5 times to get me home, each time was a fair stretch too. Full noise with the rude was 9 kph standard prop, I used to back it off to 5 kph and just enjoy the trip home knowing the rude was not struggling. I agree the aux motors are a pain for the extra weight, space taken up ect, but by hell they are the ducks nuts when the main donk gives out. I no longer have an aux on my present boat as I purchased the whole rig new and I now have 110% faith that I will get home every time. The aux back up I have now is the membership of the vmr.

Justin Rossiter
11-05-2013, 01:28 PM
Thanks for the replies, being Hobart it can be quite isolated down south if things go wrong and if the weather cuts up rough you want to be getting in quick. As I often have he kids and Mrs with me I really need the peace of mind. Will probably go for something in the 5hp range.

mal555
12-05-2013, 02:36 PM
Thanks for the replies, being Hobart it can be quite isolated down south if things go wrong and if the weather cuts up rough you want to be getting in quick. As I often have he kids and Mrs with me I really need the peace of mind. Will probably go for something in the 5hp range.

Tasmanian boaters don't enjoy the same VMR coverage/support as mainland folks, also you will no doubt trail the boat to other statewide destinations away from the Derwent Estuary that will put you into even more remote territory.
As you say peace of mind is worth heaps in this environment, also a completely separate fuel supply for aux., replenished fresh at the start of each season.

billfisher
12-05-2013, 04:47 PM
It's good being able to get back under your own steam rather than relying on someone else. The shortcoming can be got around with a bit of forethought. Eg if you have to carry a fuel tank then you can put it on the opposite side to counteract the weight of the aux. An extra tank is handy in anycase, eg if you get water contamination in your underfloor tank or run it out. It have a shortshaft Tohatsu 18 hp with a special prop and with an adjustable bracket have not had any problems with drowning the powerhead or the prop getting air. On a 5.4m boat it doesn't upset the trim too much.

Crocodile
12-05-2013, 10:13 PM
Hello Justin,

A 5hp will not be enough, I have tried a 5hp on 5m boat and it wouldn't have enough power to push you into the wind, Try for an 8hp. If you look at the specs an 8 will weigh only 5-6kg extra and provide heaps more power.
As Stevej says get a low pitch three bladed prop.
I have used the standard 2 blade and the 3 bladed prop was much better.

I have only been to Tas on holidays but I agree the weather and conditions are much tougher than the benign Gold Coast.

Justin Rossiter
13-05-2013, 11:05 AM
Thanks Croc

Just the info I needed

Cheers

Oceanranger24
14-05-2013, 09:34 AM
Hi Justin,
I have a 7.4 glass boat and last spring had the misfortune to have the engine fail to start.... 100km from home on the 'shelf'. Turns out the brushes on the starter motor had died. The Suzuki 175 2008 with 2150hrs has otherwise been perfect but not this day. I have a little yamaha 8hp 4 stroke.

Logic...
1)runs on same fuel as main engine
2) glass bowl water separating fuel filter negates 99.9% of fuel problems
3) was second hand and cheap
4) only is needed for occasional emergencies

Preparation...
1) made a mount that has donk at a good level.
2) bolt motor on floor under forard deck. negates balance problems
3) removed and rebuilt controls as levers that are 'tiny' and out of the way
4) repitched the prop to get revs as high as possible.

So.... 3pm auxiliary is fired up. 5kph is top speed. 7 pm we make Cape moreton, 8.30 combyutro pt. 4.30 am colmslie boat ramp.
And the little yammy survives for another day.... Hardly another boat on the whole journey as it was sunday evening.

That is why you carry an aux.