yamaha 90TLRA charging/running volts output?

[SeaDawg3]

I have just the opposite.
Battery @ 12.7+ and seeing 15+volts. the electronics and radio is such a small draw even it only has a .2 volt drop when they are all on.
This very well could be normal, but since I have no history or any documents on maint/service, it doesn`t hurt to throw a few parts at it and keep the old as spares.

[SeaDawg3]

ok, as ya`ll know I have 2 batteries. one 5 mons old and the other 2.5 yrs old.

they both maintain 13+v on the battery tender and go green in short order.

I just finished replacing the reg/rectifier and here are the results.

Old battery fully charged with 12.8 after settling.
fire up the boat and see 12.8. 13.0, 13.2 up to 14.4-6volts from idle to 1500 rpm.

the new battery is on the tender and sitting at 13.15 v.
swap out the battery and immediately I see 15.4 at idle and can see 15.6-8 when rev`d to 1500 rpm...

not much of a difference but an immediate difference.

with either battery I can pull it down some by operating the trim, set a few minutes and refire, same results, brings the charging current up quick enough...

what does this tell me about the 2 different batteries?

there is a small variation of readings between the fluke meter and the actual Yamaha multi gauge. .5v to be exact.

ex: at the battery 14.7 at the dash, 15.2 this is on the new battery.

keep in mind that I never lost any water in the cells.


1st pic, older battery
2nd pic, newer battery

[zenoahphobic]

ok, as ya`ll know I have 2 batteries. one 5 mons old and the other 2.5 yrs old.

they both maintain 13+v on the battery tender and go green in short order.

I just finished replacing the reg/rectifier and here are the results.

Old battery fully charged with 12.8 after settling.
fire up the boat and see 12.8. 13.0, 13.2 up to 14.4-6volts from idle to 1500 rpm.

the new battery is on the tender and sitting at 13.15 v.
swap out the battery and immediately I see 15.4 at idle and can see 15.6-8 when rev`d to 1500 rpm...

not much of a difference but an immediate difference.

with either battery I can pull it down some by operating the trim, set a few minutes and refire, same results, brings the charging current up quick enough...

what does this tell me about the 2 different batteries?

there is a small variation of readings between the fluke meter and the actual Yamaha multi gauge. .5v to be exact.

ex: at the battery 14.7 at the dash, 15.2 this is on the new battery.

keep in mind that I never lost any water in the cells.


1st pic, older battery
2nd pic, newer battery

One has higher internal resistance which means it has lower capacity, either made like that (small) or more likely ageing on the way out.

Sometimes people get fooled thinking a battery is real good because it charges quickly and to a"higher" voltage. When this happens the battery is mackerel. And because of this high voltage its deterioration is accelerated by overcharging,

[SeaDawg3]

they are both 690cca, one is 5 months old and the other is 2.5 yrs.

the older battery has the lower numbers.

the newer battery shows 15.2+ right off the bat, are you saying the new battery is toast?

[zenoahphobic]

ok, as ya`ll know I have 2 batteries. one 5 mons old and the other 2.5 yrs old.

they both maintain 13+v on the battery tender and go green in short order.

I just finished replacing the reg/rectifier and here are the results.

Old battery fully charged with 12.8 after settling.
fire up the boat and see 12.8. 13.0, 13.2 up to 14.4-6volts from idle to 1500 rpm.

the new battery is on the tender and sitting at 13.15 v.
swap out the battery and immediately I see 15.4 at idle and can see 15.6-8 when rev`d to 1500 rpm...

not much of a difference but an immediate difference.

with either battery I can pull it down some by operating the trim, set a few minutes and refire, same results, brings the charging current up quick enough...

what does this tell me about the 2 different batteries?

there is a small variation of readings between the fluke meter and the actual Yamaha multi gauge. .5v to be exact.

ex: at the battery 14.7 at the dash, 15.2 this is on the new battery.

keep in mind that I never lost any water in the cells.


1st pic, older battery
2nd pic, newer battery

they are both 690cca, one is 5 months old and the other is 2.5 yrs.

the older battery has the lower numbers.

the newer battery shows 15.2+ right off the bat, are you saying the new battery is toast?

From the evidence YEP.

Unless you fried your new regulator between changes of batteries.

To test take both batteries to a reputable dealer that can do a heavy load test. My wife has been told to get a new batt for her diesel Prado because they "tested" it. I cannot distinguish this as it starts "cranks" energetically.

New batteries can fail, they can die simply because they have been left discharged.

[SeaDawg3]

Unless you fried your new regulator between changes of batteries.

New batteries can fail, they can die simply because they have been left discharged.

how can the new reg fry just between batteries? the volts dropped when the older battery was placed back in the boat.

the newer battery is on the bench and reading 12.88V it starts and operates the boat fine.

I get the load test, done a million of them back in the day. but I`ll get it load tested.

the old battery in the boat now even after the trim has cycled a few rounds is reading 12.78 -12.8

with the old battery still in the boat, the gauge is reading 14.6 in short order.


why the sudden jump to over 15 with the new battery?

yes it could be fubared, but I`ll bet it would have ran for however long if I didn`t think the original charging voltage of 15.4-6 was high. or not even having a volt gauge to notice.

In reading some of Boscoes threads/posts, it has been know for the smaller/medium hp outboards to have a higher voltage with no load.

my original thought was the reg/rec, and it didn`t hurt to swap it out as the one I took off could very well be 13 yrs old... and now I have a spare for the tool box.

I haven`t run the boat yet as in leaving the dock and running at speed, so I`ll note what voltage I have when I get a chance to test after the incoming rain leaves us...

BTW these are deep cycle batteries if that makes a difference. this was in the boat when I purchased it.

[zenoahphobic]

how can the new reg fry just between batteries? the volts dropped when the older battery was placed back in the boat.

the newer battery is on the bench and reading 12.88V it starts and operates the boat fine.

I get the load test, done a million of them back in the day. but I`ll get it load tested.

the old battery in the boat now even after the trim has cycled a few rounds is reading 12.78 -12.8

with the old battery still in the boat, the gauge is reading 14.6 in short order.


why the sudden jump to over 15 with the new battery?

yes it could be fubared, but I`ll bet it would have ran for however long if I didn`t think the original charging voltage of 15.4-6 was high. or not even having a volt gauge to notice.

In reading some of Boscoes threads/posts, it has been know for the smaller/medium hp outboards to have a higher voltage with no load.

my original thought was the reg/rec, and it didn`t hurt to swap it out as the one I took off could very well be 13 yrs old... and now I have a spare for the tool box.

I haven`t run the boat yet as in leaving the dock and running at speed, so I`ll note what voltage I have when I get a chance to test after the incoming rain leaves us...

BTW these are deep cycle batteries if that makes a difference. this was in the boat when I purchased it.

Start with your last point, deep cycle batteries do make a difference. My remarks relate to ordinary lead acid cranking or starting batteries!

Typically these starting batteries have "impurities" added to the lead to enable them too produce short bursts of high current; the bad side is their life is only 2,3 or 4 years or so. So we tend not to worry about hitting them with high charging currents.

However deep cycle batteries are designed to give more capacity for much longer time (years).
They are far more fragile as far as current capacity as the plates are made with purer soft lead.
Now I am not sure what is the maximum current draw is, but I suspect you may exceed this when you crank your engine.
The test you should now be performing is their actual amp hour capacity, not high current. This can be setup yourself by putting a 5 amp load and measuring the time taken for the battery to go down to 11 volts at this load. Multiply hours taken by 5 and see how this compares to the rated amp hour.
Others may say a lower load to 12 v?

This will show whether your batteries have been damage as well as an indicator of life left.

I am pretty certain that you will be advised to buy a cranking battery for starting and use the other two, if OK, to power all your other uses.

Without going into depth you have many options how to set this up.

To be sure your engine output is not well regulated if you see more than 14.5v ( Boscoe alluded to). If you find it OK to continue as you are, you atleast need to put an extra regulator before your batteries!

[SeaDawg3]

Thanks Zeno.

I`d have to think Yamaha got it right with the current rec/reg, and the superseded reg I just installed. I`m more inclined to think the differences are in the battery`s.

There is only one location for The starting battery. There is an additional battery tray installed under the helm in the console. That is for the deep cycle battery that powered the *****ing motor.
There is no *****ing motor anymore.
This Battery for the *****ing motor is isolated from the rest of the electrical system. There is no connection, with the exception of the old *****ing motor harness.
I`m going to say that the PO removed the *****ing battery as necc to refresh.

I`ve read that Yamaha does not recommend an AGM type battery.
But in another boat (non yamaha) I had used the same AGM deep cycle for starting for years. I know not apples to apples.

ok, so now the requirements would be starting a 90HP outboard and running the Hummingbird/lowrance/stereo while underway or when idling.

If I stop for lunch or to hang out I usually do not run the accessories and if I do I keep an eye on the volt gauge.

time for coffee...

[boscoe99]

Thanks Zeno.

I`d have to think Yamaha got it right with the current rec/reg, and the superseded reg I just installed. I`m more inclined to think the differences are in the battery`s.

There is only one location for The starting battery. There is an additional battery tray installed under the helm in the console. That is for the deep cycle battery that powered the *****ing motor.
There is no *****ing motor anymore.
This Battery for the *****ing motor is isolated from the rest of the electrical system. There is no connection, with the exception of the old *****ing motor harness.
I`m going to say that the PO removed the *****ing battery as necc to refresh.

I`ve read that Yamaha does not recommend an AGM type battery.
But in another boat (non yamaha) I had used the same AGM deep cycle for starting for years. I know not apples to apples.

ok, so now the requirements would be starting a 90HP outboard and running the Hummingbird/lowrance/stereo while underway or when idling.

If I stop for lunch or to hang out I usually do not run the accessories and if I do I keep an eye on the volt gauge.

time for coffee...

Once upon a time they did not. Now they do.

Strange how an AGM would not work well with Yamaha's for a number of years and then all of a sudden, with the stroke of a pen, they are perfectly fine.

As long as a deep cycle battery can provide the needed starting current while maintaining voltage they can be used to start a motor with no ill effects to either the motor or the battery. I doubt that the motor knows or cares where it is getting its electrical power from during the start process.

[SeaDawg3]

Thanks Boscoe.
if I were to quote the manual, a 380CC @ 0°F with 124 reserve is what was necc back in 02.

I currently have 690MCA with 101 @ 1ah. it spins the 90 over very easy.

what this is all about is verifying the original what I thought could be a potential issue with higher charging and running voltage.

there is a difference between 2 like batteries that are both fully charged.

the newer of the 2 show an immediate 15.2+ volts shortly after starting the engine, and if I reinstall the old battery the voltage is 14.6-8 shortly after starting the engine...

I`m just looking for confirmation that the system is ok and doing it`s job with the new reg/rec in place...

is the higher readings normal? this is with no load and just the engine running. turning on the acc like radio, lowrance and Depth only drop it .2V...

that`s all I`m trying to accomplish is what is the norm and what is not.

SM calls for 14.6, well the charging does climb to 15+ as it did before installing a new reg/rec.


before I purchase a new "starting battery" I`m looking for clarification.


it just made sense to update the reg/rec with new from the 13 yr old part, now I have a spare...

I would think the trim would pull down the battery more than the starter. when I get the chance I`ll test the voltage drop wen starting. when the engine is running and I trim, I can def see the volts drop and recover.

[boscoe99]

I don't think that you have a problem.

[SeaDawg3]

I don't think that you have a problem.

Thanks B,

is it ok to use a "starting battery" to run the boat with the few electronics on while running?


personally I`ve never run down any battery from a depth/gps or radio in any of our boats or cars while just sitting for a little while w/engine off...

there are so many threads on this with cross information it`s nuts...

[boscoe99]

Thanks B,

is it ok to use a "starting battery" to run the boat with the few electronics on while running?


personally I`ve never run down any battery from a depth/gps or radio in any of our boats or cars while just sitting for a little while w/engine off...

there are so many threads on this with cross information it`s nuts...

Certainly you can use just a starting battery to power the electrics/electronics while the motor is running. Or, for a reasonable period of time with the motor off. We do this all of the time in our automobiles and trucks.

The thing about a starting battery is that it is more susceptible to being somewhat damaged if and when it is run to depletion. A deep cycle, not so much.

A lot of battery usage has to do with the application. Some motors will run without a battery at all. Some motors can be manually started without a fully charged battery. So, no risk if the battery gets to low to start the motor. If you are in lake and can't get a motor started it is one thing. If you are 50 miles offshore it is something altogether different. A number of saltwater users like to have one battery dedicated to the electronics/electrics and one battery dedicated to starting the motor. The battery not dedicated to the motor can be used to start the motor in the event that the start battery does not start the motor.

All this stuff about batteries can make ones eyes spin and head turn. Some is useful and a lot is rubbish.

[SeaDawg3]

this is where I`m at:

in my mind I have 2 questionable batteries, barring that I have not done a Load test yet on either.

the older everstart 24DC came with the boat in the starting location.

The under the helm location was empty, the PO removed his *****ing battery.

I removed the old *****ing motor and did not replace it.

the fuse buss/bar is tied into the running system of the boat and not isolated in any way. The original FF is still functioning and tied into the fuse buss as is the radio and VHF. (not original)

scenario: bought older boat with unkown battery, the first thing was to purchase a new one, and since I saw an everstart DC from 2013 in and still working, took a chance and bought another of same kind...

BUT and this is the kicker, it was the only one on the shelf, and anywhere withing a good distance from us.
when I got the battery home I opened it up and saw the water levels were low, I could see the top of the plates. so added the correct amount of Dist water and toss on the maintainer. it ook a long time to get up to max charge.
I`ve been running this in the boat since may with weekly/bi-weekly runs of 20+ miles average.

sine the boat had not come with a volt gauge, I installed one bc I think they are important to have. now upgrading to the yamaha gauges revealed a slightly higher charging voltage.

hence where we are at now...

so to complete the circle of repair/maint I`m thinking to get just a new starting battery for what you mentioned, while running I can use my simple electronics or for a very short period the vhf or radio/ff/GPS...

and not running down the starting battery.

I can and will have the better DC battery under the helm.

eventually I can rewire with a separate fuse block, the FF, radio/GPS to the DC battery and charge as necc...

B what do ya think?


you are correct, my eyes are bleeding with reading a hundred threads on the subject from THT. lots of opinions.
My automotive/truck/farm/industrial gas and diesel exper tell me differently, that what`s makes the information inconsistent.

I can run electrical equipment with the engine off on a known good system with a known good battery for a long period of time before the equipment would flounder to start...

oh my eyes...

so that`s where I am at...

something like a Deka/Duracell 650CC starting battery...

slim pickins around here, so I`ll have to look and see what I can find...
even no stock on Interstate in my immediate area...


the reserve cap or ah are not listed for some of these starting batteries...

[SeaDawg3]

so far the Deka/Duracell that I found locally is the 800cca and 1000 MCA and not the 550cca 650 MCA I was looking for. out of stock on the lessor battery. closest one is over an hour away.
said they don`t stock anything smaller... w o w ...

the 800 cca/1000 MCA is def overkill, ok for the few dollars more but...