Battery and alternator

[Losure222]

Hi all,

I just purchased my first 1993 persuader 218 with the mercruiser 350.

The alternator and battery is bad, and the battery isn’t the correct one. Can someone tell me which alternator and battery I should buy for this boat.

Thanks!

 

[Jimway]

Get the right alternator. A marine type alternator wont emit any type of spark under normal operation. Abnormal operation should be avaided. This is extremely important in the scheme of things and will do its part to minimize ignition, explosion, and/or fire and the likelihood of getting the lake above the boat instead of the lake below the boat. Not sure of what you might have presently. Most alternators can be repaired fairly easily and inexpensively. Since the alternator gets its que from the battery, a faulty (or wrong) battery (or wiring) might seem to indicate a bad alternator. Batteries can be an interesting read as to the type and size and nearly everyone has an opinion as to which is best, kind of like which oil filter is best (and watch that discussion go up in smoke). I'm guessing that you are talking about the 'starting' battery. Probably need a battery rating somewhere in the neighborhood of 700 marine cranking amps (MCA) and 120 ampre hour (Ah). You're going to be looking at basically three different types of battery construction, ie, wet cell, gell cell, or AGM- absorbed glass mat. A wet cell 'marine' type (heavier constructed) might be a good and budget friendly way of getting out on the water right now.

 

[PA-Checkmate]

how do you know the alternator is faulty?

 

[Losure222]

Thanks for the replies.

My boat is having some issues and I think it’s electrical so I’m starting with a new battery, alternator, and starter. I’ve already replaced the plugs.

My boat with a brand new battery has a very hard time turning over. It’ll take 20 cranks before it fires but it barley wants to crank over as if the engine has a load against it.

Once it fires and runs it is flawless and doesn’t have any issues. It just starts rough as if it’s a low battery even though it’s brand new.

Has anyone had these issues before?

 

[Jimway]

Lots of possibilities here. Verify (clean and tight) all grounds. Hot leads also. I just can't stress how many times I've found bad ground connections that cause all kinds of grief. Load test battery before you replace it or haul it down to the battery store and have them do it. A small capacity battery will cause slow starting issues and not have enough power left over to light the ignition system while cranking. A bad starter will drag things down too. Check voltage at alternator while engine running. You should see a voltage greater than 13 volts. Is this a hot start issue or does it do it cold also. Some advanced timing will cause a hard start issue like this too.

 

[PA-Checkmate]

Here's how to check the + and - battery cables with a "voltage drop test". The circuit needs to be under load while testing...

battery cables while starter is cranking with spark disabled
alternator engine running and all loads turned on
loads = everything turned on, lights, radio, blower, etc.

here's a good link, but also can google voltage drop test
https://www.fluke.com/en-us/learn/blog/automotive/electrical-automotive-troubleshooting


and yes... timing can be advanced to much for base timing