How much thrust and what shaft lenght should I use?

[Big Unit]

Hi,

I have a 19' bowrider. Around 2500lbs. I'm looking to buy a bow mountTrolling motor. I've just bought the boat and didn't put it in the water yet so I don't know exactly what lenght of shaft I need. Anyone knows a way to calculate this?

Also, will 55lbs thrust be enough to steer my boat?

Thanks!

 

[Huron Angler]

Re: How much thrust and what shaft lenght should I use?

55lbs will move your rig around a bit...assuming there is no wind or current. I'd feel better with at least a 75lb on a boat over a ton.

If it's for fishing on small lakes on calm days the 55 would cut it though.

 

[nimmor]

Re: How much thrust and what shaft lenght should I use?

If you can afford it go with the larger trolling motor. As far as shaft length I believe most larger thrust motors have a longer shaft, but you need to put ti in the water and see where the water line is to be sure. The propellor needs to be at least 6" under the water for quite operation.

 

[Silvertip]

Re: How much thrust and what shaft lenght should I use?

Several things to keep in mind. Any motor over 55# thrust is a 24 volts and as such requires two deep cycle batteries wired in series. If you don't have room for them that becomes a major consideration. As for shaft length, you need to get the boat in the water and measure from the top of the bow to the water line and add at least one foot to determine shaft length. Having the prop six inches in the water is not enough. any wave action at all with have it surfacing almost constantly. A longer shaft than you need is better than one that is too short. Motor height is adjustable but only if the shaft is long enough. Lastly, unless you are a die hard fisherperson you really don't need more than 55#. I have a 55# MinnKota PowerDrive V2 on my pontoon and it works just fine. If your trolling is for long periods at moderate to higher speeds than you definitely need a 24 volt motor.

 

[Big Unit]

Re: How much thrust and what shaft lenght should I use?

I'm fishing 1 to 2 times a week and max 4 hours each time. I won't have to troll a lot. The main purpose in my case is to have a stealth aproach. That's all. So, speed here is not a priority. I want to flip my jigs in a 10 to 20' range without spooking the fish.

Thanks!

 

[Big Unit]

Re: How much thrust and what shaft lenght should I use?

What can happen if the shaft lenght is too long?

 

[bigskiohio]

Re: How much thrust and what shaft lenght should I use?

you can adjust them up. the head will be higher. but you cant make them longer.

 

[bigskiohio]

Re: How much thrust and what shaft lenght should I use?

****

 

[Silvertip]

Re: How much thrust and what shaft lenght should I use?

Nothing. If you fish shallow water you can simply loosen the clamp and raise the motor. The issue is having a shaft that is too short so the prop can't stay under water in rough water.

 

[Big Unit]

Re: How much thrust and what shaft lenght should I use?

This mean, I can buy a trolling motor with the longest shaft length available and it should be ok?

 

[Silvertip]

Re: How much thrust and what shaft lenght should I use?

Certainly. But remember that when the motor is stowed, the long shaft sticks into the boat farther. Generally not problem since the motor should be mounted at an angle so when stowed it follows along the side rather than down the middle of the boat.

 

[Silvertip]

Re: How much thrust and what shaft lenght should I use?

Certainly. But remember that when the motor is stowed, the long shaft sticks into the boat farther. Generally not problem since the motor should be mounted at an angle so when stowed it follows along the side rather than down the middle of the boat. On a bow rider you will probably NEED the longest shaft anyway.

 

[Big Unit]

Re: How much thrust and what shaft lenght should I use?

Is it possible, on some boat, that the longest shaft available isn't long enough?

 

[Silvertip]

Re: How much thrust and what shaft lenght should I use?

Yup -- on the Edmund Fitzgerald the longest shaft would not be long enough. The only way you will know this is to measure your boat from bow to water and add one foot. Best I can dol. If you can't get a shaft that long you would be out of luck. Getting a shaft specially made means the leverage on that shaft from the motor would bend it. I can't believe a 60 inch shaft is too short for your boat.

 

[Big Unit]

Re: How much thrust and what shaft lenght should I use?

That's what thaught

Thanks guys!

 

[Big Unit]

Re: How much thrust and what shaft lenght should I use?

lol....

I don't know if it can help to confirm if 54'' will be enough but I pick a tape and took some measurements. My boat is on the trailer right now. The lowest part of the V hull is at 15'' above the ground. And from the ground, the nose of my boat is at exactly 54''. So, if the boat was on the ground, the nose would be at 40'' from the ground. I assume that a 54'' shaft length would be enough, right?

....sorry but I have to buy the trolling motor soon. Don't have time to put the boat in the water and I want to be very sure before purchasing.

Thanks again!

 

[CheapboatKev]

Re: How much thrust and what shaft lenght should I use?

Measure twice, cut once.

If ya want it right, put her in the water...Rushing in purchasing a $200-300 plus item without knowing exactly is a bit foolish...

 

[Silvertip]

Re: How much thrust and what shaft lenght should I use?

The difference between a 54 and a 60 is insignificant. Why would you possibly buy a 54 and end up too short? A 60 inch is adjustable for height. You can't lengthen a 54 if it's too short. You can only do that by replacing the shaft. If you have a water line on the boat use that as a reference.

 

[rndn]

Re: How much thrust and what shaft lenght should I use?

The best thing to do is to put it in the water first. I'm sure 55# will be plenty of power and as stated you only need 1 DC battery instead of 2 or even 3 for the 36 volt motors.

 

[John_S]

Re: How much thrust and what shaft lenght should I use?

If this is a fiberglass bowrider, you would want to spend some time figuring out exactly how and where you will run the mounting bolts and what kind shimming, etc might need to be done. An alum bowrider will probably have a flatter and easier surface to deal with. Measure and understand as much as possible before buying.