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Battery power issue?


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Boat seemed to run a little rough when I left the dock but not bad........ Under full throttle it ran perfect the whole way out. When o slowed down to check the water temp I could tell it was still running a little rough but again not skipping hard. After thirty min being out there I hit the down rigger to come up and immediately the boat bogged down and stalled. Took me ten min to bring in all the tangled lines, but after the boat fired right back up. Touch a down rigger and she would drop the rpm's immediately. My thought was new plugs new battery? Any suggestions. 89 305 Trophy with omc with electronic ignition.

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I have two batteries. 1 is 1 yr old second is 3 yrs old. I normally put them on charger before I head out but skipped it last couple times because I never seem to have an issue. Although it aways sucked the rpms down when I use a down rigger however this time it stalled it

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Edited by Jeremy Goodison
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Check both batteries for 12.2 to 12.8 volts unloaded. If one has a shorted cell due to a plate warpage it will not register full 12 volts even when your charger says it is fully charged. One shorted cell will kill the two batteries when tied together in parallel. When your engine is running it uses 12 volts to run ignition properly. Low batteries can cause a skip at low rpm because your alternator is turning slower with lower output. Any draw from accessories will pull enough away from the alternator at low speed to kill the ignition primary. It needs at least 11 volts to keep running. Check your alternator out put amps too if you can find a meter.

Mark

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Today I pulled both batteries and charged them all day. Fired boat up and purred like a kitten even when using riggers. It definitely was due to my batteries being low. I have a Perko selector switch but when i looked up the wiring diagram they had both batteries on full time (not isolated). When I wired all my riggers and accessories off the second battery appearantly it didn't matter. Normally I would always charge batteries night before however this season I have not been, because I never had an issue. Im assuming all the trips so far, I'm depleting more than I'm charging and it finally caught up to me. Tomorrow I'm going to try and isolate the batteries properly and then buy a third spare that stays full charge in the boat. Thanx everyone for the replies

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Edited by Jeremy Goodison
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You are best to install a marine built in battery charger. My boat is always on charge when it is parked. Winter or summer. The batteries are always up even after many years. They have a high charge rate, a finish charge rate and a maintenance charge rate where a tiny pulse is sent to the batteries every few seconds without a trickle type charge that boils the water out of solution. I never add distilled water to the batteries either.

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Being I have F&F Starter and Alternator, my shop is in Kresgeville Pa, have been in business since 1983, the marine industry has been one of the most controversial field at our meetings, earlier Mercruiser, Volvo Penta, whether powered by Chrysler, Ford, GM, they wanted us to keep the charge rate at 13.8V and no lower then 13.5V where Ford always had a higher charge rate at 14.8 batteries won't "cook" until they reach 15 volts, so we hade special regulators to install in the alternators. Their train of thought was many continuous hours of use would over charge batteries, and if a regulator opened up a little it still would be below the 14V and still be safe. They were more concerned with the gasses that the battery gives off once they get hot, most units were in in the 39 to 55 amp area, as time went on and electronics become more demanding they pumped up the voltage to 14V. Then they Mercruiser went to foreign company called Mando and they produced a 65 amp alt. That was adjustable, all you had to do is remove the 4 screws that held the Reg. On and they would set the voltage to suit the boats needs, 13.5 to 14.2 with the motor running you just needed to turn a little screw on the inside of the Reg. We needed to keep a close eye on this as the Regulators were not set and on a rebuild we needed to adjust these Regs. Which we usually knew what the customer had or wanted and would set the voltage to suit their needs. Now they have Delco, Valeo, Mando all depends who throws the lowest number at the manufacturer, all the new units come with a fixed voltage regulater usually at 14.1. With the new fuel injected motors and all the newest electronics, a boat designed for fishing has a higher bigger Alt. than a boat designed for Pleasure other than big cabin cruisers, Another reason they got away from a Delco alternator was the manufacturers found out that us rebuilders were boosting up Alts. to suit the customers needs, we were building 100 amp units and keeping the voltage at 13.8 which saved batteries and the guys had all the power they needed!! Lights, riggers, airaters, refridguaters you name it, that didn't suit the manufacturer, but what they didn't know is they kept the same mounting design, so we would just swap out the foreign units and put in a Delco unit, but soon they caught on and switched up the brackets that only that unit fit in its place. I just replaced the Alt. in my boat and I put a Delco unit in place of the old Mando, the one I built is 130 amp and voltage is set at 14.1 since I did this my motor runs smooth, more electric to the points, batteries are topped off at all times, funny thing is with the old Mando unit at 13.8 volts my guage ran in the upper half of green, now I'm border line in the green red but I know I'm at 14.1 the old school guage reads different. Delco is back into the picture with the new 7SI which is 70 amp and the voltage is set at 14.1. They also have a 5SI which 50 amp units voltage is 14.1 also. Just a little info from the rebuilders corner. Pap.

Edited by pap
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Batteries have an internal resistance of 1.5 volts so no charging begins until your 12.5/12.8 voltage is above the added resistance. That is why 14+ volts are needed to start charging your battery.

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Batteries have an internal resistance of 1.5 volts so no charging begins until your 12.5/12.8 voltage is above the added resistance. That is why 14+ volts are needed to start charging your battery.

That's correct Jim, that's why its very important to have no less than 1.5 volts difference between your battery and the hot lead to the alternator, any more resistance in that line will make the alternator work harder than it has to. If the alternator can't reach the 14.1 volts the regulator will be in the charge mode constantly, this creates heat which raises havoc on the rectifier which will result in a premature failure, and the next unit you bolt on will do the same!!

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