running gen while moving

I have a 1988 3818 Bayliner getting ready to start the loop.
Trying to learn the boat on the Upper Mississippi.
I found out when I disconnect from shore power and traveling
the inside outlets ie lights, fans don't work unless I keep the
genny running.
Question, does the frig usually shut off when traveling or does the
battery bank run the frig till I run the genny or get hooked up to
shore power again ?
Any guess as to how long the frig can stay off and not ruin the food.

AGH, I don't want the beer to get warm.

I had a 1986 38 Bayliner for a few seasons.
- The stock reefer is duel voltage 120/12 and will switch to battery power anytime A/C power is removed IF the 12 volt reefer breaker is 'on'.
- There are plenty of stock 12 volts lights that will work with the A/C disconnected both fluorescent and typical bulbs. Any 120 volt lamps or fans that were added will need the genset running which we did often at speeds from 6 to 17 knots.


With that said you now own a boat that is 30 years old and the previous owner(s) may have changed many things.

No inverter on board?

I could not find one but looking to up date many things
when I get the boat down to Mobile for a complete refitting.

ctbarbarian said:

I could not find one but looking to up date many things
when I get the boat down to Mobile for a complete refitting.

Click to expand...

The 12v breaker for the reefer is labeled - on the 12 volt panel not the A/C panel - is that set to 'on'?

smitty477 said:

The 12v breaker for the reefer is labeled - on the 12 volt panel not the A/C panel - is that set to 'on'?

Click to expand...

And to answer your other post about both manual heads -
- Are you sure the intake screens were not painted shut?
- They may need a little help from wear/drying out
The cylinder has a bottom edge with an "O" ring around it. Replace the "O" rings and use a little 'superlube' on the ring and tube insides. If the intakes are clear this will help prime the system and make it work until you can do further repairs if/as needed.

yes, boat was painted a month ago.
I called the shop and asked any ideas about why
the bowls wouldn't pump water up.
The head shop guy told me "I bet that idiot kid painted
the holes shut "
I might need a haul out to clear them and I'm not paying
for their mistake.

ctbarbarian said:

yes, boat was painted a month ago.
I called the shop and asked any ideas about why
the bowls wouldn't pump water up.
The head shop guy told me "I bet that idiot kid painted
the holes shut "
I might need a haul out to clear them and I'm not paying
for their mistake.

Click to expand...

When you divorce the boat from shore power. Do you reposition the 'transfer' switch?

ctbarbarian said:

yes, boat was painted a month ago.
I called the shop and asked any ideas about why
the bowls wouldn't pump water up.
The head shop guy told me "I bet that idiot kid painted
the holes shut "
I might need a haul out to clear them and I'm not paying
for their mistake.

Click to expand...

They can put it in the slings and inspect the inlet.

I have 3 choices, shore, genny, off
When I disconnect from shore, I usually leave the switch
in the position that I will probably use next.
Should I set it to off ?

ctbarbarian said:

I could not find one but looking to up date many things
when I get the boat down to Mobile for a complete refitting.

Click to expand...

Do the running lights work?

They want me to try to close the seacock,
disconnect the toilet intake clamps,
slowly open the seacock and see if water comes in.

That should tell me if the outside is painted over or the
hand pump is the problem.

yes, running lights work, but I noticed the fans and plugs in
didn't work when disconnected .
FM radio worked, airconditioner didn't

Everything "working" is DC. Everything "not working," including air conditioner is AC - so you either need your generator or an inverter running off your house - though the inverter will not run all AC - including the air conditioner.

I need more time on my boat to learn it better,
I get so confused, easily on this electronics stuff.
I pull teeth and hurt people for a living,soon to be retired, this is a new learning experience for me.

ctbarbarian said:

yes, running lights work, but I noticed the fans and plugs in
didn't work when disconnected .
FM radio worked, airconditioner didn't

Click to expand...

The A/Cs wont work w/o running the generator running.
The FM radio is no doubt 12vt.
The outlets are 120vt.
The fans? Are they 12vt or 120vt?

Check the transfer switch is to the generator output.

Even if you have a good size inverter onboard, you cannot hope to run the A/Cs.

Even if you have an inverter onboard you might have only 1 or 2 120vt outlets available when on the inverter.

How many house batteries are onboard and what are their size?

Remember, even if you have a BIG inverter on board, without the ME or Generator running, you will draw the batteries down to 'flat' quickly.

Remember the phrase "load management". When everything goes dark, you are sucking too hard on the straw. Start shedding loads while watching the Amp meter.

The boat, is it a 30amp or 50amp boat?

ctbarbarian said:

yes, running lights work, but I noticed the fans and plugs in
didn't work when disconnected .
FM radio worked, airconditioner didn't

Click to expand...

Please forgive me if this sounds insulting, I just don't know the extent of your experience.


You have two type of powered devices on board, 12v DC and 120v AC. When plugged in or have the genny running, you have 120v AC powered to the panel. That will power any 120v items. Those will include your Air Conditioning and anything that is plugged into a standard 120v wall socket. As was mentioned, originally the fridge was a 12v/120v convertable so it would run on either. Unless you have a propane stove, that too will require 120v AC to run.


Many boats have an inverter. This converts your battery 12v DC to 120v AC. This is great for running small loads, or short term loads (such as a fan, iphone charger, coffee maker) but won't handle big loads or you will quickly drain your batteries.


So, if you had the boat surveyed before you bought it, the survey will show if you have an inverter or not. If you didn't have it surveyed, then you need to start hunting around the boat to see what you have.

"They" want you to?
How far are you from the marina?
Take it back to the marina and let them to put it in the slings to solve this mystery.

It would probably take him 10 minutes to check it himself, probably will be a lot more time, effort and gas to have them check.

Steve91T said:

It would probably take him 10 minutes to check it himself, probably will be a lot more time, effort and gas to have them check.

Click to expand...

Yup. Plus, if they are not painted closed, then the marina may want to charge him for the lift and hang inspection.

30 and 50 amp plug cords
2 main engine batteries for twin diesels and 1 battery for gen.
3 aux batteries.
AC/DC norcold fridge.

I did have it surveyed and I can't find any reference to a inverter.
Survey says "wired for 110v "

I'm about 40 miles downstream from the marina and I can make it back up
this weekend, I was just hoping it was something simple and I could fix it
myself.
My experience with this large a boat is from the fall of 2017, I'm very pontoon
river savy but none of them had this many systems.
I appreciate any and all information.

Hey that was me last year. The biggest boat I owned was a 20’ bow rider. Now we have a 31’ Mainship with two engines, an generator, and more systems than I thought were possible on a boat. I didn’t understand them at all. But once you figure it out, it’ll all make sense. Now we are under contract with a 47’ Marine Trader. I’m know I’ll be asking all kinds of similar questions again.

For our boat, the panel is labeled AC and DC. AC is for shore power and generator. DC is what can be run off the batteries which are charged by the alternators.

On the AC side are the big ticket items. That’s your stove, microwave, battery charger, water heater, AC’s outlets and also the fridge. Without the gen or shore power, they won’t work. The DC side will work anytime off the batteries. Running your mains will keep the batteries topped off.

The DC side has the little things like lights, fresh water pump, head, and also the fridge. So when on shore power, I run the fridge off that, the Ac side. When underway with the generator off, I run it off the dc side...off the batteries.

When underway if we need coffee, or a breakfast Sammy warmed in the microwave, the generator needs to be started.

I hope this helps a little! Don’t feel bad, it’s confusing.

ctbarbarian said:

30 and 50 amp plug cords
2 main engine batteries for twin diesels and 1 battery for gen.
3 aux batteries.
AC/DC norcold fridge.

I did have it surveyed and I can't find any reference to a inverter.
Survey says "wired for 110v "

Click to expand...

Sounds like no inverter then. So anything that is plugged into a standard wall socket will not work unless you have your genny running or are on shore power. Interior lights will be 12v so will work fine and your fridge will work on either. There isn't a problem running the genny while you are running the boat when you need to run the AirCon. However, I would not run the genny just to keep your 110 outlets running for small loads.

ctbarbarian said:

I need more time on my boat to learn it better,
I get so confused, easily on this electronics stuff.
I pull teeth and hurt people for a living,soon to be retired, this is a new learning experience for me.

Click to expand...

Ha!....rest assured...your boat will eventually repay you for all the pain you caused others...Boat Karma!!
I have one frig that is 12v/120v, and one (icemaker/frig) that is 120v only...discovered that on the maiden cruise to home port when the ice started melting. Now if we are using the smaller frig, I just fire up the inverter while underway.
Enjoy the new ride!

30 AND a 50 amp cord? Now that's a first for me.

ctbarbarian said:

I need more time on my boat to learn it better,
I get so confused, easily on this electronics stuff.
I pull teeth and hurt people for a living,soon to be retired, this is a new learning experience for me.

Click to expand...

Perhaps go to the Bayliner site and click on owners resources and then 'manuals"...
https://bayliner.com/owners-manual/

Put in your year (1988) then your model (Mty) and download the manual. These are not detailed as much as the later years but it will provide a general description of what is on the boat / where the stuff is / and a general wiring diagram.
Do you have gas engines or Diesel? Do you have engine manuals?
The rest you can pick up from other owners at the BOC.

OldDan1943 said:

30 AND a 50 amp cord? Now that's a first for me.

Click to expand...

There is a parallel switch inside and there are two AC units - 16KBTU and 12KBTU.

smitty477 said:

There is a parallel switch inside and there are two AC units - 16KBTU and 12KBTU.

Click to expand...

Are you sure you dont have two 30amp cords? One 30 amp cord for the A/Cs and the second amp 30 amp cord for the rest of the boat?

We are all working on the assumption that hull valve is open.

OldDan1943 said:

Are you sure you dont have two 30amp cords? One 30 amp cord for the A/Cs and the second amp 30 amp cord for the rest of the boat?

Click to expand...

I am not the original poster - I am just familiar with these boats.