190 MONTAUK Transom-mount Trolling Motor

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
SkipJack
Posts: 11
Joined: Sun Nov 22, 2015 5:13 pm

190 MONTAUK Transom-mount Trolling Motor

Postby SkipJack » Wed Nov 30, 2022 11:45 am

Q1: based on your first-hand experience, will using a Minn Kota 55-lbs-thrust 12-Volt electric trolling motor mounted on the transom of a 190 MONTAUK give sufficient control of the boat?

BACK STORY: I have a 2008 Montauk 190 whose chief use in the summer is trot-lining for crabs. I live along the Chesapeake Bay. Trot-lining is a two-man job: one crew pilots, the other screw scoops crabs from the trotline. A key to the operation is holding a straight course when deploying the trotline and then holding a course beside the line when scooping. I can't do it alone - I've tried and it's a comedy of errors. And even with two people, a 10-knot wind can make holding course challenging. The Montauk with its wide deck is a bit of a kite.

I can't always find a crabbing partner, though bribing my kids works about half the time. I'd like to crab solo. I'm considering a trolling motor mounted in the starboard side of the transom. Folks on a crabbing forum I frequent have urged me to buy a 14-foot Jon boat instead. I'm still exploring the trolling motor.

The 190 MONTAUK boat weight including fuel and gear is estimated to be 3,000-lbs. This is not much over the recommendation for a 55 -lbs-thrust electric trolling motor. Minn Kita estimates for every 2-lbs thrust a motor has, that motorit will be able to move around 100-lbs of boat weight. On that basis a 55-lbs-thrust motor should move 2,750-lbs of boat.

I figure my total boat weight is 3,000-lbs and a 55-lbs-thrust motor should be okay, as long as I don't try to move at a boat speed of 5-nautical-miles-per-hour all the time. A 55-lbs-thrust motor can operate from 12-Volts. More powerful motors need more battery voltage.

jimh
Posts: 11670
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 190 MONTAUK Transom-mount Trolling Motor

Postby jimh » Wed Nov 30, 2022 12:16 pm

I don't understand why you think an electric trolling motor mounted at an offset at the stern will hold a straighter course line than the 190 MONTAUK boat's main propulsion engine mounted on centerline. Rather than a trolling motor, I think you need an auto pilot if you want to operate as a one-man crabbing crew.

SkipJack
Posts: 11
Joined: Sun Nov 22, 2015 5:13 pm

What is an Auto-Pilot

Postby SkipJack » Wed Nov 30, 2022 5:03 pm

What is an auto pilot?

jimh
Posts: 11670
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: What is an Auto-pilot

Postby jimh » Wed Nov 30, 2022 5:29 pm

Read at

Lowrance Outboard Pilot Hydraulic Pack
https://continuouswave.com/forum/viewto ... ?f=9&t=535

An auto-pilot in the realm of outboard engine boats is a device that controls the steering of the outboard engine. The steering control is usually implemented by including an electrically operated hydraulic pump into the existing hydraulic steering on the boat. Only the steering is controlled, and there is no interface from the auto-pilot to the throttle control of the engine.

The auto-pilot moves the outboard engine steering based on output from its controller to the electrically operated pump. The controller tells the pump in which direction it should pump hydraulic fluid in the existing hydraulic steering system on the boat and the duration of that pumping action

The decision made by the controller about which direction to pump and duration of the pumping is based on the boat's present heading compared to the previously established desired heading or based on returning to the previous trackliney and then resuming the previous heading if the controller is integrated with a navigation computer that has established a predetermined route the boat should be following and computes cross-track error.

The controller may also get input from a rudder position sensor, however less expensive systems do not employ a rudder position sensor and try to keep track of the rudder position based on having learned how quickly the rudder (which in the case of an outboard engine is the engine itself) responds to input of hydraulic fluid flow. If there is no rudder position sensor then the hydraulic system must be symmetrical in its response to movement in both directions, a characteristic called a balanced actuator. If the hydraulic system is unbalanced, that is, if its movement in one direction is not exactly the same as in the opposite direction, then a rudder position sensor is needed. The implication is thus that hydraulic steering systems which use side-mount actuators cannot work with an auto-pilot that does not have a rudder position sensor input because most side-mount hydraulic steering actuators have slightly unequal movement of the actuator in one direction compared to the opposite direction. Note that in inboard engine boats with a separate rudder, the hydraulic actuator might be unbalanced.

Outboard engine powered boats that use mechanical cable steering systems are generally not easily adapted to auto-pilots. The steering mechanism at the helm is usually replaced by a new mechanism that can be controlled by the auto-pilot controller and will have an electric motor that can move the steering wheel.

SkipJack
Posts: 11
Joined: Sun Nov 22, 2015 5:13 pm

Re: 190 MONTAUK Transom-mount Trolling Motor

Postby SkipJack » Thu Dec 01, 2022 11:09 am

Terrific information, thanks, I'll explore the auto pilot option.

SkipJack
Posts: 11
Joined: Sun Nov 22, 2015 5:13 pm

Re: 190 MONTAUK Transom-mount Trolling Motor

Postby SkipJack » Thu Dec 01, 2022 11:39 am

On second thought the auto pilot system is expensive and there are pages of installation instructions to cover what the manuals leave out. Not the solution I'm looking for.

I think I found the perfect and cheapest way to go: a steering control arm. Steering not the throttle is the main concern. https://www.westmarine.com/forespar-ste ... 81368.html

I can set the throttle to its minimum forward setting, steer with my left hand on this gizmo and net crabs with my right hand.

jimh
Posts: 11670
Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
Contact:

Re: 190 MONTAUK Transom-mount Trolling Motor

Postby jimh » Sat Dec 03, 2022 10:52 am

SkipJack wrote:...the auto pilot system is expensive...

The Lawrence Outboard Pilot is only about $1,000. I don't think that can be considered expensive if compared to your initial plan to install an electric trolling motor.

The cost of the total installation of an electric trolling motor would probably be greater than $850. You would have to buy and install all of the following:
  • the trolling motor, whose installation on the transom as you specified would be difficult because the notched transom of a 190 MONTAUK is probably too narrow to have a trolling motor mounted there alongside the main propulsion engine; the cost of such a trolling motor is probably at least $250; the cost of fashioning a mounting system is probably at least $100, and also involves labor and perhaps modification of the boat;
  • a large storage capacity battery to provide 12-Volt power to the trolling motor that is completely separate from the engine cranking motor having about 50-Ampere-hours of capacity or more; such a battery will cost at least $350;
  • a battery charging system for rapidly restoring electrical charge to the trolling motor from 120-VAC power when at the dock; such a charger will cost at least $150.
With these estimates the total cost of the electrical trolling motor purchase and installation is going to be about $850, but that is for a trolling motor of only 55-lbs thrust, which is likely to be unsuitable for giving good control to a 190 MONTAUK boat as a stern-mounted propulsion engine. You probably would be better served by a more powerful electric motor running of higher voltage. That change would probably double the costs of the electric trolling motor solution you initially proposed.