Operating without alternator hooked up

[Seevee]

Is there any reason that one couldn't run a boat with the alternator(s) disconnected?
Alternators are mounted and belt installed so water pump will work, but no electrical connection so they would just spin.

Would only need power to start, and operat minimal electronice. Generator can provide the power.


I see no harm, but would like the collective wisdom of the experts here.

 

[syjos]

Is there any reason that one couldn't run a boat with the alternator(s) disconnected?
Alternators are mounted and belt installed so water pump will work, but no electrical connection so they would just spin.

Would only need power to start, and operat minimal electronice. Generator can provide the power.


I see no harm, but would like the collective wisdom of the experts here.

I have a switch on my dash to turn the house battery alternator off.

I turn off the alternator when I know that I will be plugging in at a marina and the run time is less than a couple hours.

Also if I'm running generator underway.

 

[Rebel112r]

I had an alternator fail, ran for a week without it. Had some solar and generator to use when needed. Picked up a truck alt in Wrangell to get by and had a replacement marine alt waiting in Juneau. All in all, just a bump in the road. This was on a Cummins 330.

 

[DavidM]

Should work fine. The tach may not work depending on the type.

David

 

[Alisske]

I have a diesel, old school, all gears. Ran it for a month or so why figuring out alternator issue. No problem whatsoever.

If its a modern engine, or gas EFI or something, you have to make sure battery can power that stuff

A,

 

[SoWhat]

Is your goal is to reduce load on engine? The difference between an unloaded alternator and a fully loaded alternator would probably be quite small in terms of hp. I would guess running a separate generator would be much more inefficient. If your are running a 6hp generator to eliminate 1HP drag of the alternator you are not gaining much.

But the direct answer to your question is you do not need an alternator as long as you have a good battery.

 

[Simi 60]

Went through two continuosly rated large frame alts trying to charge house bank while underway - they worked for several months but eventually gave up.

Now we don't have an alt at all, instead have a 24v smart charger connected to starts

 

[koliver]

My first diesel sailboat, while still under construction, without any battery aboard, nothing to connect the alternator to, ran to move the boat a few times, up to an hour at a time. Hand crank to start.

 

[Comodave]

My first diesel sailboat, while still under construction, without any battery aboard, nothing to connect the alternator to, ran to move the boat a few times, up to an hour at a time. Hand crank to start.

How does that hand cranking thing work out on your current boat???

 

[koliver]

How does that hand cranking thing work out on your current boat???

All in proportion.
First was a Yanmar 1 cyl, 12hp. Crank supplied with the engine, installation permitted cranking while on my knees, with my chin inches above the counter above the front of the engine. (30' sailboat).
The effort was just below impossible for me at age 28.

Present are 6 cyl, 200hp. no crank available, nowhere to sit or kneel in front of engines.
Effort would be well above impossible, if I could even try.

Different problem than what the OP wants to hear about.

 

[Brisyboy]

Bit of a perhaps silly non techo question but does it do the alternator any harm creating the electricity with nowhere for it to go?

 

[diver dave]

Bit of a perhaps silly non techo question but does it do the alternator any harm creating the electricity with nowhere for it to go?

Its a good question. The OP said to disconnect electrically the alternator. That would mean it can't produce power, since there is no field current available. Note though, that there are "one wire alternators", that when they spin, they will self-excite, and they don't likely want to be disconnected.

 

[psneeld]

My question would be why?

With reasonable maintenance and not severely overloading it during its life, failure is pretty rare.....for any reason.

If it is necessary to be installed for the belt to turn the water pump...there would be no reason in my mind to disconnect it electrically. If you can take the belt off and drive the engine circulating pump with a shorter belt and keep it tensioned...that migh eliminate a tiny bit of lessoning a failure point.

But I just see no need.

Would it hurt? As Dave pointed out...and I am not sure about one wire alternators and even others not liking an electric disconnect.

 

[diver dave]

Actually, this thread hits home. I burned out a new 60 A alternator just last month. Likely trying to charge my Li bank a bit too aggressively. 2 weeks into a 8 week sail. Live and learn…

 

[jgwinks]

As far as I can tell, running even a one-wire alt disconnected won't hurt it, as long as it was disconnected before starting the engine. There's no load so no power would be produced. Disconnecting while running is a different matter, that will blow the diodes in the alt. That's the "producing electricity with no place to go" scenario.

 

[cafesport]

As has already been pointed out it mainly depends on how your alternator is regulated. Because of a failed external regulator I learned early on you don’t need no stinking alternator when running. We ran for months before replacing the regulator just running the generator as needed. Engine room was noticeably cooler (-15 deg) as well. After we added another small genny we found that it’s more efficient to let it handle the battery charging while underway. Our alternators were capable of producing 8 kw though our batteries and house loads rarely exceed 5.

 

[Flyguy1967]

You will not have a problem. Did the sea trial of my boat with the starboard disconnected because the buyer had scheduled the haul out and sea trial which could to be moved and he could not wait for the replacement to arrive.

Everything ran great and boat close today