Trolling Motor Size For Tandem Island

Hi!

I'm going to use the FPV Power Hobie motor mount on my TI to help make some of our family trips a little more convenient. I'm hoping to get some experienced feedback.

Here's what the motor mount looks like.
https://www.mariner-sails.com/motor-mou ... drive.html

My wife and I take our three small kids and dog out on the kayak. It's a lot of fun, but coming back into the wind is tough. All of us including the weight of the kayak are about 900-950 pounds. I was looking at getting a watersnake 24# motor and 35ah battery. I'm hoping that could push us at about 4mph for an hour and a half. We could sail for about 6 miles and then slowly motor back for 6 miles.

I don't want to get a more powerful motor because it would require a heavier battery (and it's all more expensive)

Would this 24# motor and 35ah battery setup do what I'm hoping it would?

Here's the motor
Watersnake - ASP 18 and 24 Pound Thrust 12V Saltwater Trolling Motor, Transom or Kayak Mount https://www.amazon.com/dp/B007NVNPM4/re ... UTF8&psc=1

Here's the battery
Mighty Max Battery 12V 35AH Replacement Battery Compatible with Minn Kota Sevylor Light Trolling Motor Brand Product https://www.amazon.com/dp/B00K8ECOCK/re ... UTF8&psc=1

Thanks for any feedback!

I'm not sure if you're trying to do this on a low budget, but there are far better and much more effective ways to add motor power to a TI which have been discussed in detail on this forum. Albeit, they are more expensive.

You can add a 2.5 HP Suzuki gas outboard motor for around $750 for the motor and about $100 for the mounting parts or you can add a Torqeedo or Evolve motor for around $1800.

Powering a TI with a trolling motor will not produce great results either in propulsion or range, so most TI owners use either the Suzuki or the Torqeedo.

Please see these threads for a start:
Outboard Motor / Hobie TI Application Guide & 403 Comparison
Torqeedo 403 Ultralight Motor / Hobie TI Application Guide

Once you add up the cost of the FPV mount, the trolling motor, and the battery, you're roughly in the same ballpark as the Suzuki motor but with a lot less power and range. I'm not sure that I see the appeal. Also, that little 35 Ah battery alone weighs almost as much as the Suzuki motor and won't provide much range.

If you would like to stick with the trolling motor, then at least consider using a 12 Volt LiFePO4 battery rather than a Lead Acid. You'll get twice as much power/range with half the weight and it will last years longer. These factors easily justify the higher upfront cost.

Thank you for the info! I had no idea a gas motor to weigh so little.

Cost is a major factor for me so the $1800 options are not being considered right now.

I got the FPV power motor mount at a bit if a discount, so the whole setup will cost me about $500. It's about $325 cheaper than a gas motor option from what I can tell. Now I'm thinking I might need to hold off on this project until next year and save a bit more money to get a gas motor. I'm conflicted now.

If I'm stuck with this 24# motor/35ah battery setup, how do you think it will perform? I could see maybe going to a 35# motor and a 65ah battery, but that's a lot more weight.

I appreciate the links to other form threads. I'll look at those as well.

It all depends on what your requirements are based upon given your specific needs and what body of water you'll be using it on.

The TI is a relatively large kayak, it takes a lot to propel it. A smaller trolling motor should provide ~3 MPH while a larger one might provide up to ~4 MPH or perhaps a bit more. You may need to change to a prop more suitable for efficient propulsion rather than for trolling though.

The range depends upon the battery and how fast you wish to go. The 35 Ah Lead Acid battery might get you around 4-8 miles at moderate throttle, the 65 Ah battery might get you 10-15. Due to all the varying factors, you really won't know until you test it. If you have all the key specs for the motor and battery, you can at least calculate the theoretical range.

This is all in relatively calm water. If you ever find yourself in heavy currents or waves, the motor might become overwhelmed. If the forward speed goes below 2 MPH, steering will become adversely affected. Don't ever rely on only a trolling motor in rough conditions. Trolling motors were designed for fishing, not for reliable forward propulsion. It's always iffy to use a motor for something other than what it was designed for.

A 2.5 HP Suzuki gas outboard will reliably propel you up to 7 MPH. Its range is only limited to the amount of gas onboard. You can easily stow a gallon of gas on a TI in small fuel bottles. One gallon of gas will give you a range of around 25-35 miles or more depending upon how fast you wish to go. It will continue to propel you in rough conditions and you can rely on it to get you safely back to shore. Its capabilities far exceed those of a trolling motor for reliable forward propulsion.

So, again it all depends upon what you're looking to get out of the motor option you choose.

I understand that money is a concern, but for the money vs performance, the Suzuki really can't be beaten. The primary downside IMO to the Suzuki is the noise. Some people don't mind it while others may find it tiring. Gas motors can be tedious compared to quiet, clean electric motors.

Unlike trolling motors, Torqeedo electric marine motors are specifically designed for boat propulsion and will work much better than a trolling motor for this. However, I fully understand if they are too expensive for your budget, a lot of people feel the same way. Cost is the biggest disadvantage of the Torqeedo option.

The downsides to your trolling motor propulsion setup are the lack of power, the lack of range, and the relatively poor performance and weight of a lead-acid battery. You can fix the battery issue though. You would get twice the power, twice the range, and twice the life out of a 12 Volt LiFePO4 battery and they're half the weight. But yes, they cost considerably more.

It's hard to power any boat on a low budget. If money is the key factor, then the Suzuki is still your best option as it gives you the best overall performance for a reasonable price that most TI owners should find affordable. Additionally, the installation and use of a 2.5 HP Suzuki gas outboard on a TI are well proven from many TI owners' experiences (including mine) and relatively risk-free. So, given your specifics, that would be my recommendation.