Electrical Question - Bilge Blower Wiring

Dan H · Post by **Dan H** » Sun Jan 01, 2006 8:50 am

On my boat, I have re-installed the saildrive engine. I was not planning on installing a starting battery, it's only 15hp. The more I think about it, the better things would be with one. The main reason is because the engines electrical system is already factory wired to use it's own battery. The house bank can be completely separate. The starting battery will be charged from the small internal engine charger (3amp) and the house batteries will be charged from belt driven alternator (35 amp). This gives me two completely separate systems.

The starting battery, and it's isolation switch, will be located inside the engine compartment. This way, I have to open the engine compartment before energizing that electrical system. The house system has the standard 1-2-BOTH disconnect switch that can be accessed from inside the cabin. If the blower is wired from the house bank, I could run the blower before energizing the engines electrical system.

The question is, which electrical system should the bilge blower be supplied from, the house batteries or the starting battery?

Post by **Tim** » Sun Jan 01, 2006 10:18 am

I'd run it off the house bank. This keeps your engine system completely separate and just for engine cranking.

bcooke · Post by **bcooke** » Sun Jan 01, 2006 2:32 pm

Interestingly, I chose the opposite argument. I chose to put the blower on the engine electrical system. If the house bank is dead then I can still run the blower and start the engine. If the engine electrical system is run down to where I can't run the blower then I won't be able to operate the engine starter anyway. You could start the engine and with the alternator producing power then run the blower but I am pretty fanatical about running the blower prior to engine start.

The need to factor this into the electrical system is pretty limited I think. The chances of running the house bank down so low that the blower won't work is pretty remote. A more likely scenario is that there is a fault in the house system the shuts down everything on the house system and prevents the blower from working at all.

Ultimately, either way probably works fine. In both installations, a set of jumper cables between the battery banks will cure most anything.

-Britton

wstokes · Post by **wstokes** » Sun Jan 01, 2006 3:39 pm

I would agree with Tim, it should be run from the house system. In any case you should probably look at replacing the battery switch with a parallel mini switch like the one Blue Sea sells. I am replacing my basic battery switch this year as it was the partially the blame for frying my handheld GPS this past year. As well this type of switch allows you to connect the house with the engine system if needed to in an emergency.

A30_John · Post by **A30_John** » Sun Jan 01, 2006 6:13 pm

I am replacing my basic battery switch this year as it was the partially the blame for frying my handheld GPS this past year.

How so?

wstokes · Post by **wstokes** » Sun Jan 01, 2006 7:37 pm

How so?
When crossing Trinity Bay last summer I realized that I had forgot to switch from my starting battery (No.1) to my house battery (No.2) after about 2 hours sailing. I was using my radar and my handheld GPS (Eagle Explorer) was plugged in to my 12volt outlet. So I reached into the boat and switch from No.1 position to No. 2. The voltage drop as the switch was being used and the GPS could not handle the voltage drop and then died. A couple of months later the Eagle Explorer dealer next to my place of work told me that the older Eagle Explorer models could not handle varying levels of voltage. This has since been corrected with the newer models.

Shark · Post by **Shark** » Tue Jan 03, 2006 4:50 pm

Two years ago I witnessed a runabout with an inboard engine explode and burn only a few yards away from the gas dock. The driver escaped with his life, just, and the boat was a write off. It took a very long time to extinguish the fire. Portable extiguishers were inadequate and only a tug with a water canon finally brought it under control!

It was an memorable illustration of how dangerous gasoline fumes can be.

Lyman

Dan H · Post by **Dan H** » Tue Jan 03, 2006 6:38 pm

That's why it is so important for me to get it right. My wife gets very sick in just a few seconds being around diesel so there won't be any of those in my future, unfortunately.
Thanks for the replies,
Dan

Curmudgeon · Post by **Curmudgeon** » Wed Jan 04, 2006 7:03 pm

My wife gets very sick in just a few seconds being around diesel so there won't be any of those in my future

Hehe, I'm assuming you mean there won't be any DIESEL in your future, and not the other way around. You never know.... some people are really attached to their diesels.