motoring

[Guest wwbaginski]

Hi, just purchased 2.3 hp honda short shaft for my BRS17 at a  good price so some  "improvements" are necessary now -as the transom has been built for a long shaft outboards.  I'm envisaging various motor brackets. The question is how deep (or better: how shallow) should I keep the shaft anticavitation  plate under the water surface? I don't mean most wanted by producers but practiced out to be still ok? just for trolling.  any other experience or impression from motoring seventeeners will be appreciated.

[Ken_Potts]

I've got a Honda 2HP long-shaft motor.  I think as long as the plate is lower than the bottom of the boat you should be fine.  I can't remember exactly where the plate is on my boat but I know I would have tried to install it that way.  The motor works great.  I've used it in dead calms, of course, but I've also used it to get back to the dock (straight upwind) when the wind kicked up to more than I could handle under sail.

[Tom Lathrop]

What Ken said is true for boats in general but there are exceptions.  In a small boat powered with a small outboard other things may take precedence.  At the low speed you will be running, drag of the lower unit is not a big issue so having the propeller deeper in the water will not be a problem there.  It is nice not to have the propeller ventilate when a passenger moves forward and lifts the prop out of the water which may happen if the depth is set in "normal" position.

In your case, I would set the lower unit a couple inches deeper than normal unless the draft is a problem.

[Ken_Potts]

That's a very good point, Tom.  It's been a while since I used my motor for more than a few minutes at a time and I forgot that I have experienced exactly what you describe when I have the crew weight too far forward during a no-wind fishing trip.

[Peter HK]

Hi Wojtek

I have an adjustable bracket and positioned it so the second lowest of the 4 adjustable heights was set at the outboard manufacturer's recommended height ie this allows me to lower a further 4 inches or so if necessary. This very low setting helps prevent ventilation in waves, on turns, when heeled, or with crew on the bow but it still happens occasionally. Other advantages of the bracket are that the motor is off the transom and doesn't catch the mizzen sheet, and motoring in very shallow water is possible with the bracket in a higher position- I can set it so the prop is just below the transom but not below the keel depth so if the boat can float then motoring is possible.

Some disadvantages are cost, weight (of bracket and also by moving the motor further aft there is more weight in the end) and possibly aesthetics for some.

I'll attach a couple of photos

Cheers

Peter HK

[Guest wwbaginski]

I'm still thinking on a motor mount, however -  last but not least - what would you say about an ultrasimple solution borrowed from Sea Pearls. I mean a removable board mounted horizontally to the transom on the proper height for short shafters?  The motor becomes a side motor instead of a rear one.

I can figure that in a Sea Pearl case, as an "almost double ender" ,  the motor remains "inside" boat's beam, and in case of BRS it would remain fully "outside" the beam, but do you think it's 13,5 kg (? lbs) would make a big deal and cause a damage of a BRS stability?

I've been inspired with this nice photo of "Lively" having a Sea Pearl aft in the background:

I will appreciate your comments.

[Hirilonde]

I suppose that if the motor and the board/bracket could be easily removed on the water and stored in the boat while sailing it would be OK.  It isn't so much the stability as what happens when the boat heels over while sailing.  I have a friend who uses a home made side mount bracket for his Rozinante as there is no transom to mount on. The bracket mounts just a little aft of amidships.  He keeps his tiny kicker and the bracket stored below and uses it extremely rarely.  I would think that even if you designed a workable bracket like you show that a short shaft motor would still work poorly in any kind of waves. 

[John Turpin]

I'd be very worried about the forces on the transom that would be created if you heeled at speed and dragged your motor bracket.  You'd have to really reinforce the transom--just in case.

[Ken_Potts]

In gusts, my boat has often heeled far enough to put the outboard end of that motor mount under water.

You should be able to fabricate a bolt-on mount that sits low enough on the transom for the short shaft motor.  Actually, the lower you can get it the better (within reason) because the mizzen sheet likes to wrap around anything that is above deck level.

[Guest wwbaginski]

yes the mizzen sheet is a pain and only Peter HK and Wes Kisting have solved this problem as far as I know, each one in a different way.  My idea of using a short shaft outboard on Doppio comes from the second activity, river cruising on the boat with low transom - it's one motor for two boats.

In fact I only want (actually I have to, due to harbour rules) to iddle on the harbour of Gdansk internal waters - about 10 km long way to the historical port where the marina is located - and another 10 km back to the gulf. And go upstream on the delta rivers - that's  why I skipped an electric outboard and took modern 4 stroke one.

Anyway, thank you for all those informations - now I understand better what might happen while on the gulf.

[Peter HK]

The motor becomes a side motor instead of a rear one.

I'd be worried that motoring in anything other than calm conditions wouldn't be possible as, with any roll, the prop would ventilate as it's so far from the midline.

Cheers

Peter HK