Aerotec with 8HP - will it plane?

Fenlander · 26 June 2018, 14:05

For reasons that will be mentioned soon in my Fowey sibbing thread I am currently running a Mariner 8HP 4-stroke OB on the Aerotec.

I explained to Mrs Fenlander that it would restrict us to displacement speed under 6kts as I was sure there was no chance an 8HP would push the draggy Aerotec up on the plane.

I was gobsmacked to find I was wrong. With a passenger load of 21 stone it planed easily to (an albeit modest) 12.5kts and with a passenger load of 27 stone it still crept to a 10.5kt plane.

Genuinely surprised as had anyone asked on here re that combo I'd have said not a chance.

MCL · 26 June 2018, 14:29

This is really interesting, I have just sold my 2015 Yamaha 8hp 2s. Paired with a correctly inflated (using pressure guage) zodiac fastroller 325.

Myself at 75kg, I could plane at a maximum 17mph. wife, dog, baby would slow us down to displacement at 9 mph, we just got it onto the plane when surfing the wake of a boat.

I have now got a 2004 mariner 15hp 2s.

Fenlander · 26 June 2018, 14:31

Mariner 15 still suiting you MCL?... they are truly excellent sibbing motors.

MCL · 26 June 2018, 14:37

Yes well I will be honest I am nervous about writing about it on here as the fastroller 325 is rated at 10hp. Obviously you know this having owned one.

I have justfied it my own head as a temporary arrangement, when funds allow I will buy a new honwave 320ie from Ely boat chandler's.

I have used the mariner once on the Nene, I'm sure you know once you get out of pboro towards dog in a doublet lock there might be the opportunity to test the engine.
We * might* have recorded 19mph on the GPS fully loaded with family onboard.

I know you were giving me alot of advice regarding the Suzuki efi 20, for which I am very greatful. In the end it was driven by fianaces, I sold the 8hp yam and brought the mariner 15hp and came out with a £300 profit to put towards the honwave.

I look forward to hearing about your change to the 8hp.

Max... · 26 June 2018, 14:51

Outstanding OB the Merc/Mariner 15 2 smoke. The Fastrollers are quick too - not draggy like the Aerotec. 9.8 on ours (ex-David) used to do 17.5 kts or more 1.5 up.

Fenlander · 26 June 2018, 15:07

>>>I look forward to hearing about your change to the 8hp.

More of a temp rental really... but as I say more info to come.

HUMBER P4VWL · 26 June 2018, 16:50

2.5m Avon RiB - Tohatsu 8hp 2 smoke - planes with 25stone and does 21mph with 14stone. [emoji106]

lightning · 26 June 2018, 17:16

Same here, Zodiac 285s will get to 18mph with two of us on board
Tohatsu 9.8hp two stroke.
With my previous engine a Mariner 6HP it still achieved 14mph with two of us on board, although my missus had to sit at the front until it got going.

Billybruiser · 26 June 2018, 17:49

I was out on my Avon 2.8 rib being pushed by a merc 10 2 stroke, and on my phone app it hit 25mph with just me on it (16 stone) I was very surprised 😯

Fenlander · 26 June 2018, 20:31

Well we've finally found a crew weight that will hold it back.

35 stone crew maxed out at 7.5kts displacement speed.... no surprise really.

Fenlander · 26 June 2018, 20:32

>>> dog in a doublet lock there might be the opportunity to test the engine.

Ah the official Cambs engine test area!

Simon1973 · 27 June 2018, 23:19

This is gonna sound really dumb, but what is planing?
I have a honwave t32 v floor and a honda 8hp 4s.
No idea what planing is, or if its done it!!

Lee1 · 27 June 2018, 23:49

Planning is when the boat rides on top of the water, if you've done it I think you would know as the steering becomes lighter and the bow rises then drops down, have a YouTube search, getting up on the plane and the actual planning is not so dramatic with a v floor as it is with a flat floor, with one person and a fully working 8hp you should have just about planned I feel but maybe not, could be you engine trim is not set right (Also YouTube that) maybe consider a bigger engine you will plane for sure and the whole experience is worth it rather than just going at pre planning speed and displacing water (you automatically plane once you achieve 8-10mph or so in your boat I believe depending on weight of course)

Fenlander · 03 September 2018, 21:26

In case it interests anyone have a look at post #37 in this thread for details of a Mariner 10hp 4-stroke on the Aerotec…

http://www.rib.net/forum/f36/mariner...tml#post781442

plymjack · 04 September 2018, 07:40

I have a 4m Waveline XT with 8hp 2-stroke Merc which will plane with 2up and do 12kts.

So was wondering how much a 15hp 2-stroke would improve the top speed?

Fenlander · 04 September 2018, 09:02

I'll answer on your own thread re upgrading your OB as it will keep replies about your boat together.