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O'Day 27 Prop

Jan 16, 2021
9
O'Day 27 27 Coronado
I just acquired a '74 O'Day that has been converted to a SolidNav electric motor. Can anyone please tell me what propeller I should have on it, or how I can find out?
 
Feb 21, 2013
3,424
Hunter 46 Point Richmond, CA
You did not say whether this was an inboard, outboard and hp. You might find this article helpful regarding propellers for electric motors.

 
Jan 16, 2021
9
O'Day 27 27 Coronado
Here is some more information about it. The SolidNav motor is inboard.

At the lowest throttle setting, the speed of the boat is too high. I need to keep putting it in neutral and only putting it in gear for a moment when trying to dock.

In open water, the boat makes about 6-7 knots at full throttle, and accelerates well.

But what is really a problem is that when the boat is moving very slowly, like when leaving the dock, deflecting the tiller to turn, especially when in reverse, the boat does not change direction.

I am having to use a small outboard motor for all maneuvers involving slow speed.

And a friend said that he thought the prop was cavitating, but I can't confirm this is the case.
IMG_0955.JPG
 
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Feb 21, 2013
3,424
Hunter 46 Point Richmond, CA
Nice description of your issues!!...........I will let others weigh in on what propeller you need, but I would contact electric motor propeller manufacturers / dealers just as we do for diesel engines for a propeller recommendation that can can warrant.
 
May 17, 2004
3,380
Beneteau Oceanis 37 LE Havre de Grace
Here is some more information about it. The SolidNav motor is inboard.

At the lowest throttle setting, the speed of the boat is too high. I need to keep putting it in neutral and only putting it in gear for a moment when trying to dock.

In open water, the boat makes about 6-7 knots at full throttle, and accelerates well.

But what is really a problem is that when the boat is moving very slowly, like when leaving the dock, deflecting the tiller to turn, especially when in reverse, the boat does not change direction.

I am having to use a small outboard motor for all maneuvers involving slow speed.

And a friend said that he thought the prop was cavitating, but I can't confirm this is the case.View attachment 189210
What you describe sounds pretty common for inboard engines. I wouldn’t change props to try to fix those problems. Any change in props will reduce your tip end performance, hurting either speed or efficiency. For me shifting in and out of neutral is just how maneuvers are done. Any engine that can produce decent top end speed is likely to move the boat way faster at idle than you would want to hit the dock at. Maneuvers should be a combination of forward and reverse to get the boat moving, and coasting in neutral to turn. You’ll likely also find that, especially in reverse, the prop walks the stern to one side or the other. Learn which direction it does and how to use it to turn the boat the way you want.
 
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Jan 27, 2008
2,994
ODay 35 Beaufort, NC
Is it possible to add a potentiometer to your circuit to lower the RPM's of the electric motor? In reverse you want to get the boat up to speed quickly then put it in neutral and let the rudder turn the boat. At very slow speeds the rudder is ineffective and with the propeller engaged in reverse the boat will turn to port. Give it a burst of speed, put it in neutral then turn the rudder. Don't turn the rudder all the way or it will act like a brake. practice going in and out of your slip until you get a system that works consistently.
 
Oct 20, 2014
135
O'Day 23-1 Lake Champlain, Vermont
I would also suggest contacting SolidNav or a SolidNav dealer to see if you can do a speed reduction to the shaft using gearing and a belt drive. Is the original mechanical transmission still in place or are you moving to reverse electronically by reversing the electric motor itself? Out of curiosity, what do you have for a battery pack? Recharging by solar or at the dock? I don't have an electric motor now but have been looking into it for my next boat.
 
Feb 21, 2013
3,424
Hunter 46 Point Richmond, CA
I would also suggest contacting SolidNav or a SolidNav dealer.................
My understanding SoliNav is no longer in business.....so suggest contacting other marine electric motor companies for help.
 
Jan 16, 2021
9
O'Day 27 27 Coronado
Yes, unfortunately, they are no longer in business and Google searches have not found me much information about the motor. When I got the boat the batteries were 10 years old, dead, and would not take a charge. I replaced them with 4, very big, 12V batteries (about $550 each - can get you details if you need it) and they are working very well. There was already a built-in battery charger for the old batteries and it is doing a good job of charging them after use and keeping them topped-off with shore power.

There is nothing remaining from the original motor, transmission, etc. The throttle just reverses the polarity to get reverse as far as I can tell.

I seem to have a range of about 30-40 miles under power at about 80% power. The batteries are supposedly recharged by the spinning prop with under sail going more than about 3 kpm. But in reality, I have not noticed any indicating of that on the volt meter.

The motor is smooth and strong, but not as quiet as I imagined it would be.