Im thinking about mounting a 74lb thrust trolling motor (motor only no shaft or head) to my 27ft hunter, and also adding solor panels to charge the batterys ,has anyone ever performed this procedure? I dont want to have to deal with taking off a trolling motor everytime and storing it, so i thought i would do it like the newer bass boats...thoughts
bottom mount trolling motor
- Thread starter christians1600
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Basic Math
Christian, this arrangement could make sense for a daysailer, but if it is to work, you'll need to do some ciphering first.
You'll need to know what the motor draw in amps, and how much time do you expect to run the motor during one outing. Multiplying the two will tell you how many amp-hours of energy you will spend on a day with perfect conditions. I'd then add 30–50% for wind, tide and other eventualities, like having to motor in from the farthest point on the playground because the wind dies completely.
You'll need a battery bank (composed of one or more stand-alone batteries) with a capacity of twice your total above, so that you can avoid discharging your bank beyond 50% on a regular basis (deeper discharges result in fewer charge-discharge cycles the battery will be able to give over its life). The 50% mark is an arbitrary number that in practice gives most folks the best overall return for their dollar. You can discharge them more deeply on occasion without much perceptible loss of life-cycles. Do it regularly, and you will notice.
Oh, and you will want true deep-cycle batteries. Be wary of a "marine" battery, which in my experience is not a true deep-cycle battery, but a general-purpose compromise between a deep-cycle and starting battery. Since you won't need "cranking amps" over a short period of time, you don't need what these batteries offer.
One question I'd have here is "What speed (over water) will that motor push my 27ft. hull?" I'm sure it will be adequate in normal conditions, but what about against wind/current? I don't know what a 74lb. thrust motor will do. Someone?
The recharging will be a function of how many solar panels putting out how much power (figure about 5 hrs/day of good output) times how many hours/days it will take them to replace the power you used. And that's a whole 'nother column of numbers to consider.
If you can put some real values into the vague outline above, you may be on your way to some happy trolling.
Fair Winds,
Jeff
P. S.— I like the idea of solar panels, but if you're in a slip with electricity, a good battery charger will do the job much more cheaply.
Christian, this arrangement could make sense for a daysailer, but if it is to work, you'll need to do some ciphering first.
You'll need to know what the motor draw in amps, and how much time do you expect to run the motor during one outing. Multiplying the two will tell you how many amp-hours of energy you will spend on a day with perfect conditions. I'd then add 30–50% for wind, tide and other eventualities, like having to motor in from the farthest point on the playground because the wind dies completely.
You'll need a battery bank (composed of one or more stand-alone batteries) with a capacity of twice your total above, so that you can avoid discharging your bank beyond 50% on a regular basis (deeper discharges result in fewer charge-discharge cycles the battery will be able to give over its life). The 50% mark is an arbitrary number that in practice gives most folks the best overall return for their dollar. You can discharge them more deeply on occasion without much perceptible loss of life-cycles. Do it regularly, and you will notice.
Oh, and you will want true deep-cycle batteries. Be wary of a "marine" battery, which in my experience is not a true deep-cycle battery, but a general-purpose compromise between a deep-cycle and starting battery. Since you won't need "cranking amps" over a short period of time, you don't need what these batteries offer.
One question I'd have here is "What speed (over water) will that motor push my 27ft. hull?" I'm sure it will be adequate in normal conditions, but what about against wind/current? I don't know what a 74lb. thrust motor will do. Someone?
The recharging will be a function of how many solar panels putting out how much power (figure about 5 hrs/day of good output) times how many hours/days it will take them to replace the power you used. And that's a whole 'nother column of numbers to consider.
If you can put some real values into the vague outline above, you may be on your way to some happy trolling.
Fair Winds,
Jeff
P. S.— I like the idea of solar panels, but if you're in a slip with electricity, a good battery charger will do the job much more cheaply.
thanks
I am only going to use it to get in and out of the marina, i will also have a gas outboard, i just like to cover all angles and I have never seen a bottom,transom mount motor on a sailboat ...thanks!!
I am only going to use it to get in and out of the marina, i will also have a gas outboard, i just like to cover all angles and I have never seen a bottom,transom mount motor on a sailboat ...thanks!!
The performance of a 74 pounds of thrust electric motor will be comparable to that of a 1 horse power gasoline engine and totally inadequate to propel an h27. Some calculations have been made to approximate lbs of thrust to horsepower but the results rendered do not reflect actual performance.
In still winds, it's possible to go back and determine what you might need by the PHRF rating. Something at 27' with a lower PHRF would be easier to drive... It's the waterline length that would be the key to relating...
By as a lot of folks have pointed out - you size the motor for the potential bad conditions... So it's good that yo know that the regular motor is still needed.
I think you have a good idea.... then again, I would.... Not long ago while pulling up to a dock, our outboard died.. we can in "manually..." had a bit of a gust.... and in the drink I go.. a backup electric motor would have been real nice... and a 74" would have done the trick... That's for a Mac26D.
No way would you want a 74# motor in wind and current conditions... but at the dock or as a backup... good idea....
-- just my "soggy" opinion..
--jerry
By as a lot of folks have pointed out - you size the motor for the potential bad conditions... So it's good that yo know that the regular motor is still needed.
I think you have a good idea.... then again, I would.... Not long ago while pulling up to a dock, our outboard died.. we can in "manually..." had a bit of a gust.... and in the drink I go.. a backup electric motor would have been real nice... and a 74" would have done the trick... That's for a Mac26D.
No way would you want a 74# motor in wind and current conditions... but at the dock or as a backup... good idea....
-- just my "soggy" opinion..
--jerry
Minn Kota is making engine mountable pods up to 200lbs of thrust (24V) that are supposed to move a 22-26 foot boat (about 3-4hp). They probably aren't made to adapt to a small sailboat outboard, but figuring out how to mount them externally might be much better than trying to mount a normal trolling motor through your hull somehow. It may be worth contacting them to see what is possible and what it will take from a battery perspective to operate for say 30 minutes. The problem is that their figures for a 22-26 foot boat likely are for a 3-5000 lb boat, not a 7-10,000 lb boat dragging a keel through the water.
If I had a very small sailboat on a lake, I'd certainly go electric, so I sympathize with you. However, I doubt it will be cheap or cost effective.
You might wish to see how much Minn Kota is willing to work with you. There is a fair amount of interest in conversions like this and it might be an untapped business opportunity for them.
Good Luck,
BobM
If I had a very small sailboat on a lake, I'd certainly go electric, so I sympathize with you. However, I doubt it will be cheap or cost effective.
You might wish to see how much Minn Kota is willing to work with you. There is a fair amount of interest in conversions like this and it might be an untapped business opportunity for them.
Good Luck,
BobM
I used to sail a C22 in the keys. I had a 5hp honda that broke down and not wanting to miss any sail time I went to KMart and bought a trolling motor and battery. It moved the boat as well as and as fast as the 5hp Honda. I just attached the motor to the outboard bracket.
After about 10 days of using the motor I almost considered using it all of the time but went back to the Honda when it was repaired. I used a shore power auto charger to recharge the battery everyday. I would guess I used it for about 45 minutes a day to get out of my slip and out in to ocean. The silence was the best part. As I recall the moter was about a 45lb thrust.
After about 10 days of using the motor I almost considered using it all of the time but went back to the Honda when it was repaired. I used a shore power auto charger to recharge the battery everyday. I would guess I used it for about 45 minutes a day to get out of my slip and out in to ocean. The silence was the best part. As I recall the moter was about a 45lb thrust.
As a trailer/daysailor I am very interested in this topic, and would love to see what has been tried and what people would do differently. The only hole in my hull at this time is the keel bolt for the swing keel, so I am not interested in mounting something on the hull, but if I could mount something to the outboard bracket that would be great.
I have a 55 lb minn kota on my outboard mount, all I use it for is going in and out of the marina. I use a 225 am-hr deep cycle battery stored where the fuel tank used to go, and have the motor on the outboard mount.
Pros: silent, instant on-forward,reverse (no shifting), 180 degree of freedom to turn with the tiller handle, awesome for docking. Motorsailing is nice too - in light air, give yourself a tiny boost to keep going through the puffs, yet still silent. Zero maintenance! I spent about $250 on the motor and battery, so it is a very cheap and reliable way to power a sailboat with no auxiliary.
Cons: Weight (battery + motor) is slightly below that of the gas tank and outboard, but available power is 1/4 of before, top speed is 3.5 knots as opposed to 6, and max range used to be about 80 miles, now it is more like 10.
What I'd like is to add a small 4-stroke motor powering a large truck alternator. about 100 amp at 14.5 volts, plus some loss, it would ned to be abut 3 hp. Obviously, larger boat, larger motoor/charging system. For extended motoring the generator could run the outboard directly. But for the everyday in-out of the marina, or just motoring in from a daysail, you would never need to touch the generator if you could plug in. Plus side: a small, quiet, portable generator has a lot more uses than just on the boat, rather than having $2000+ invested in your outboard motor.
Pros: silent, instant on-forward,reverse (no shifting), 180 degree of freedom to turn with the tiller handle, awesome for docking. Motorsailing is nice too - in light air, give yourself a tiny boost to keep going through the puffs, yet still silent. Zero maintenance! I spent about $250 on the motor and battery, so it is a very cheap and reliable way to power a sailboat with no auxiliary.
Cons: Weight (battery + motor) is slightly below that of the gas tank and outboard, but available power is 1/4 of before, top speed is 3.5 knots as opposed to 6, and max range used to be about 80 miles, now it is more like 10.
What I'd like is to add a small 4-stroke motor powering a large truck alternator. about 100 amp at 14.5 volts, plus some loss, it would ned to be abut 3 hp. Obviously, larger boat, larger motoor/charging system. For extended motoring the generator could run the outboard directly. But for the everyday in-out of the marina, or just motoring in from a daysail, you would never need to touch the generator if you could plug in. Plus side: a small, quiet, portable generator has a lot more uses than just on the boat, rather than having $2000+ invested in your outboard motor.
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