aux engine size for sr4

spud76 · 27 August 2013, 01:59

Can any of you tell me the smallest aux engine that would push an Sr4. Thanks.

matt h · 27 August 2013, 06:29

smallest you get away with is a 3 hp but you ideally want a 4-5.. hp per meter approx

clydeoutboards · 27 August 2013, 07:20

first of all it will depend on tides, currents etc oh and age of the engine as they do lose HP over time

min size would be something like the honda 2.3 and these push shetland 570/ blackhawks down the scottish sea lochs at around 4-5 mph and weigh 700-750 kg so your lighter SR4 would be fine in similar conditions.

as for needing 4-5 hp per meter please please dont go down this route as you will find even moving an old 2 stroke around when you are on the water of this size near impossible lift. also you simply dont need that amount of HP for your aux engine.

Dave

chewy · 27 August 2013, 07:37

I thought it was 1hp per metre, so about 4-5hp for an SR4.
A 2hp will still be better than nothing!

HUMBER P4VWL · 27 August 2013, 09:04

Quote:

Originally Posted by clydeoutboards

first of all it will depend on tides, currents etc oh and age of the engine as they do lose HP over time

min size would be something like the honda 2.3 and these push shetland 570/ blackhawks down the scottish sea lochs at around 4-5 mph and weigh 700-750 kg so your lighter SR4 would be fine in similar conditions.

as for needing 4-5 hp per meter please please dont go down this route as you will find even moving an old 2 stroke around when you are on the water of this size near impossible lift. also you simply dont need that amount of HP for your aux engine.

Dave

I think he meant "you need 4-5hp - (a) hp per metre"

matt h · 27 August 2013, 09:08

Yes thank you.. 4 mtr 4 hp..

spud76 · 27 August 2013, 09:25

Thanks for all the info.

ian parkes · 30 August 2013, 22:23

I have a little tohatsu 3.5 on the back of mine which is a similar size boat . Its mainly for fishing so i dont oil up the main engine .
it pushes it along about 6 knots
I think its more about wieght and size , would a bigger motor fit on the transom and would it unbalance the boat . They dont get smaller than the old 3.5 stick engines and my tohatsu 50 is pretty slim too . if i had a 4 stroke then the aux probably wouldnt fit .
My advice is borrow one and try it