10 hp motor with a generator?

[LoudDog]

I have a Johnson 9.9 HP pull start motor that I love. However, I'd prefer to have a similar sized motor with a generator to charge my electric troller's battery while running on gas.

Question 1: Can I add a generator to mine, or is it not worth the effort?

Question 2: Would pretty much any electric start motor have a generator?

Sorry if these are pretty dumb questions, other then the motor i have, I know pretty much nothing about outboard motors...

 

[Silvertip]

Re: 10 hp motor with a generator?

What you really need to know is that small outboards of any make do not have high enough alternator output to charge a trolling motor battery. Some numbers to illustrate why are:

1) A trolling motor operating at its fastest speed will draw roughly 40 amps of current each hour. Probably about 1/2 - 2/3 that at slower speeds. So remember the number 40!!

2) Most medium range 40 - 75 HP outboards have only a 12 - 16 amp alternator. Smaller engines if they have an alternator at all will be in the 4 - 6 amp range. That means at wide open throttle the alternator would only output 6 amps each hour.

3) So to replace 40 amps from the troller battery that small motor would need to run wide open for about 7 hours to charge the troller.

4) Therefore this is not a practical idea -- not even for mid size motors.

 

[LoudDog]

Re: 10 hp motor with a generator?

Thanks! Maybe if I build a canopy for the boat with solar panels...

 

[ondarvr]

Re: 10 hp motor with a generator?

Around here we troll a great deal and use a lot of electrical stuff while we do and everybody wants to charge the battery while trolling. Those that buy new get what they want (charging system) those that have older motors will put a charging system on it if they can find a good deal, possibly off an old dead motor, not many buy the new parts to do it.

At trolling speeds it may produce about 2 amps or less, which isn't much, but will keep up with a fishfinder/gps, it won't help much with our electric downriggers, crab and shrimp pot pullers or an electric trolling motor.

The normal answer from a trained service Tech is to buy a second battery, but many people "feel" better being able to charge the battery off the kicker.

We normally don't have long runs from the launch unless we head out for Tuna (50 miles), 20 minutes might be a normal long run for salmon. So if your main battery is dead and you can't start the motor you most likely won't be able to charge the battery up enough with the kicker until about the time you get back to the launch. This will allow you to start the big motor and power load though.

I don't have a charging system on my kicker, if I found a great deal on the parts I'd put one on it even knowing it won't help a great deal. I don't normally do "Feel good" things, but I'll make an exception in this case.

 

[Silvertip]

Re: 10 hp motor with a generator?

Many folks seem to look at solar panels as an unlimited source of "free" energy and therefore make a great battery charger. Sorry -- but a solar panel that would work as a battery CHARGER and not just a MAINTAINER would need to be as big as your boat. Small panels simply are no better, and actually much worse than the 4 - 6 amp alternator on a small kicker. It simply does not work. Read the specs and understand what they mean before you spend money on this stuff.