12v or 24v

I'm embarrassed to ask this question but here it goes. I'm looking at an old boat to purchase. How do I determine if the electrical system is 12 or 24 volt? At this point, there are no batteries on the boat and I just don't know what to look at to know for sure.

Thanks,

24 volt is fairly rare in sub 50' boats. What make and size boat are you looking at? If there is a shore power battery charger, it will specify output voltage. The engine starter and alternator will also have identification plates on them that will list voltage.

Ted

Thanks for taking the time to respond. I'm looking at a 1973 Eagle 40' (produced by the same folks as Marine Trader). The engines are twin FL120s.

12 volt almost 100% guaranteed. Don't think I've ever heard of a fl120 that wasn't 12 volt.

Ted

O C Diver said:

24 volt is fairly rare in sub 50' boats. ...
Ted

Click to expand...

My boat is 24-volted. I suspect this is because the builder builds mostly larger boats and for efficiency uses the same systems in it's smallest boat model.

These engines haven't been started in years. The boat is in the water. I'm not experienced with diesels but I'm trying to put together a checklist of things to do prior to even trying to start them eg. oil change etc.

You're going to want to get a large piece of paper and pencil for the amount of information you're about to receive from this forum.

Bennett, your boat is 98% likely to be 12-volt. Why not get an electrician to check it out if it's not obvious to you. First check the alternator.

Bring it on! I've got a notebook sitting her next to my keyboard and I'm here to learn.

Buying a boat that has not been run in years is typically not for the uninitiated. I hope the reason is not for low hours, you actually want to avoid that.

Are you sure you really want to go down this particular hole?

Hey Bennett, welcome aboard. The first suggestion I would make is to roll the engines over by hand using a 1/2" pull handle and socket (should be 15/16") turn clockwise (engine rotation) facing the pulley. Chances are you will spin a few degrees and let the compression "bleed" past the rings then turn some more. One revolution would do it. You just don't want to damage a piston (s) if the cylinder walls have rusted. If it begins turning and seizes up- can't go forward any more- then repost and the board can coach you on the next steps.
My opinion would be not to replace fuel filters yet. You could create a problem by introducing air that needs to be bled out. Myself- after I was sure the engine and gear had oil I would crack two injector lines (5&6) about a turn and attempt to start. One group 31 battery would probably do it, but two in parallel would be better. Give it a try- you will know within 10 seconds. If it spins slow stop immediately and find out why. Starter/ cables/ low switch wire voltage??
Once she starts be ready to kill for a few seconds until the gauge shows oil pressure. Tighten 5&6 inj lines and listen as this levels the engine out.
Purpose of loosening two is that it allows it to start on 4, but still purge any accumulated air through 5-6. Good Luck!!


1983 Present 42 Sundeck
Twin Lehman 135's

Change the engine oil, filter and the oil in the injection pump. Replace the all the fuel filters and bleed everything making sure the mechanical fuel pump works. Check the raw water impellers. Hook up fully charged start batteries and have a high amperage starting booster/charger near by just in case. Try rolling them over with the stop solenoid held on till you get some oil pressure. If they roll over and you get some pressure, at least 10psi, then try letting them start.

They're Lehmans, so more than likely they will fire right up.

After that flush out all the coolers. Easy to do with a 5 gallon flush bucket, bilge pump, feed/returnhoses and mild acid mixture while they are still mounted on the engine. Then change the tranny fluid fire than up again and see if they shift correctly. If they do run them up to 1800-2000 rpm in idle for a few minutes while looking for leaks and watching temperatures.

If all is well go for a ride and run them up to 2000 rpm or so under load and watch the temps and for leaks again for a few minutes.

If all is still well and assuming no other drastic problems have popped up, bring the engines back to 1600-1800 rpm and enjoy your first cruise.

Do I understand correctly?

Have you purchased this boat? or just looking at it?

If looking at it, where is the owner?

Check the voltage tags on one of the water pumps or macerator.