Aux engine

Ned_led16

Hi Folks,
Wondering about an aux engine for a 17-20 foot 2 stroke 90-120hp boat.

Q1:Is it stupid to put a 4 stroke 2.5 yam aux on? (suppose very messey with diff fuels)
Q2:Whats the best size to go for - 10hp - 2.5 is a bit small eh?

Q3:Is it possible to use the aux to potter about? i cant imagine a boat will drive properly with the aux engine on the side.

Q.4 Is it a balls to fit a bracket to the back of the boat or expensive or where do u get one cheap?

Loads of questions - i did do a safety boat course and powerboat level 2 - but still loads to learn!
if i were a millionair id just pay someone to do everything and call the shop and order it all but theres always the lotto

fergal.b

I would go for a 6 - 15 hp as an aux, you can have high winds,strong current and the tide working against you so the bigger the better

Yep a lot of fishermen use the aux to keep them in the one spot and for trolling .


Here is a rough price list http://www.marineparts.ie/boats-and-motors/outboard-brackets/ but they also come up on DD and ebay so you could pick one up second hand, they are easy enough to fit just 4-6 bolts depending on what weight the engine is, when the AUX engine is in the down position you want the cavitation plate level with the bottom of the boat.
Also make sure it's far enough from the main engine so when the two engines are at full turn they won't hit each other.



.

Daibheid

A rule of thumb is about 1Hp/metre plus 1. As Fergal highlighted you'd want to take into account likely conditions of use and the boat characteristics. e.g if the boat pitches/yaws a lot in chop an aux may spend too much time sucking air or some boats have a lot more windage than others.

2.5hp would be a waste plus that is quite a heavy engine.

Aux weight is another possible issue making a 2T more attractive.There's also the question of security both under way and against thieves. Big OBs are usually bolted on, small ones depend on clamps and they can work loose rattling around back there. I've found the aux transom bracket bearings and tilt lock all get a hammering. So you might want to look at storing it inboard until required.

Regarding the bracket I found a long shaft aux can sometimes be Ok clamped straight on to the transom but may drag in the water when off the plane.
As they only move you along gently leveling the anti-cav plate with the hull is not IMHO strictly necessary nor is the off-centre drive an issue.

I'd recommend pottering with it occasionally anyway to see how the boat handles, to check the aux is reliable and to keep the fuel from going off. I'd drain the carb too between uses as I had an aux carb gum up from that.