altenator?

So the saga continues with my boat. Starts fine at dock, won't start in the water. At first we thought it was altenator, so I took it out and had it tested, altenator is fine...supposedly. The shop mention something about it being a high voltage or low voltage something meaning it won't charge in idle but only in higher RPM. Anyhow, they said it was fine. So I tried to put the boat in yesterday and it took a bit to start at the dock, but fired up and ran great. One buddy rides, engine dies going from full throttle to neutral and won't start. So we flag down a boat and noone has jumper cables so I "borrow" their battery, my boat starts just fine. Would that not suggest an altenator issue? I have two batteries, that's the other thing, my boat will not start on one battery. Both register over 12.0, but won't start the boat on one or the other, must be both to start.

That whole swap battery thing suggests either bad battery (ies) or altenator, but the battery shop said both batteries are good, and the electrical shop said the altenator is fine. If you have read my post before and it is the same, I apologize. I just want to ride and trying to sort out.

IF you battery has been left on a charger and all yrou seeing is 12 volts yoru battery is dead. Have yoru battery load tested. they make hand held testers. Sound like you have bad batteries.

If you have a digital multi-meter then its time to start using it a little more precisely.

Measure the voltage when the engine is running. If you don't have at least 13.2 volts your battery is NOT charging. If your battery is fully charged and the engine RPMs are above 1500 RPM I would expect to see 14 volts at the battery.

If the battery voltage is below 12.5 volts then your battery might actually be discharging. A fully charged battery should read around 12.6 volts. When the voltage has dropped down to 12.0 volts you battery is significantly discharged.

It is possible that your alternator is either weak or you are simply drawing too much current when you ride. Are you running large amplifiers? Blower? Ballast pumps? My alternator won't keep up with all that at one time.

But the boat on a charger for 24 hours, then disconnect it for an hour, then measure the voltage on the batteries. If they are not reading 12.6 volts then I would suspect your batteries are bad. Batteries don't handle being run all the way down so if you have been running the dead on a regular basis you could have worn them out really fast.

Rod

got it figured out. The shops up here are idiots. I don't know engines at all. Self-admitted completely ignorant. But I processed the facts: batteries good? check. alternator good? check. so why would a new battery start the boat???? ding ding ding I'm finally riding problem free... the alternator wiring wasn't hooked up. traced the wire only to find that it had been taped back into itself connected to Nothing! This thing has been in the shop twice trying to sort this out. I went out for the first time the other night without any problems. Finally at the end of season, but at least its fixed