Charging voltage low on 1988 85hp?

[NMShooter]

Hmmmm.. OK.. looking at my Seloc manual.

Had my boat out for the first time today, but only did a lot of trolling. This is a no-wake lake so I could not throttle up. Seemed like my battery was draining rather than charging, as my voltmeter barely showed 12V while idling along, and my low battery signal went off on my fishfinder.

I see that this year and HP motor does not have a voltage regulator. The rectifier goes straight to the battery.

I Ohmed out the coil, and it looks good... 0.5 Ohms. I tested the bridge rectifier, and it checked out. No opens or shorts in the bridge.

Do these motors just not put out much juice when idling?

Thanks for any insight.

Frank

 

[trendsetter240]

Re: Charging voltage low on 1988 85hp?

Easy test would be to use a simple multi-meter and connect it to the battery terminals. Then start the motor, on muffs or in the water, and use the idle lever to throttle up to around 1500 - 1800 rpm.

Watch the meter for an increase in voltage. At 1800 rpm you should see at least 13 volts. If not you may need a new rectifier.

Second check is to slow the motor down to idle and check the voltage at idle. Should read at least 12.7v. If not throw a charger on that battery and leave it over night. That battery needs to hold 12.6 -12.7v after a full charge. If not replace the battery.

What kind of accessories were you running? Might be that your power load was higher than the rectifier output at idle speeds.

 

[NMShooter]

Re: Charging voltage low on 1988 85hp?

Only accessory was a small fish finder... 300mA load.

Unfortunately I don't have an idle lever on my controls.... a source of frustration for me.

I meant to take my voltmeter with me today on the lake, but the dash meter seems to be fairly accurate. I saw no difference in Voltage output from just idle to a few hundred rpm above that. I'll need to check and see what it is doing at a faster run... the bummer is that I plan on doing a lot of trolling with this motor, and I'm a bit spooked it might kill the battery on me. I'm pretty sure that the rectifier is in good shape. I'll take it into a lab tomorrow and check it out.

Thank you for the reply!

Frank

 

[trendsetter240]

Re: Charging voltage low on 1988 85hp?

Hey Frank, even if the motor won't put out much charge at idle you should be fine if you get a good battery. Look for a dual purpose starting/deep cycle marine battery that has more than 100 minutes of reserve capacity. Reserve capacity rating is at 25 amps draw.

A good battery could power that 300mA fish finder for days without going dead. Just be sure to put a charger on it or run at cruise speeds for a few hours at least once per week.

 

[cambosoup99]

Re: Charging voltage low on 1988 85hp?

yea it doesnt charge much at idle. I remember reading in the factory manual it has to be a certain rpm before it puts out enough to charge. but it shouldn't be going dead idling. was your battery fully charged up.

 

[NMShooter]

Re: Charging voltage low on 1988 85hp?

I had placed it on a charger the night before for about 6 hours. However, I don't know how good / old this battery is. I think I'll charge it up and take it to be tested.

Another question... if the battery is removed from the motor while it is running, will the motor still run? It should, right? I wonder if this might be a good acid test to see if the magneto is working properly. I don't understand why the battery seemed to have drained so quickly. I did have to crank it for 30 seconds or so to get it to fire the first time yesterday, but after it was warm it started right up each time.

 

[cambosoup99]

Re: Charging voltage low on 1988 85hp?

should never disconnect your battery with the motor running. If your battery was already low and you tried to crank it several times it probaby drained it. You'd be surprised how quickly your engine will fire with a fully charged battery.

 

[NMShooter]

Re: Charging voltage low on 1988 85hp?

It was close to fully charged before attempting the start.. It had a 12.75V float on the battery. When I returned home after 3 hours of trolling using my Force motor, the battery voltage was down to 12.25V.

No way does a 300mA fish finder put that sort of drain on the battery, especially if the motor is running / charging correctly.

I notice that my gauge lights are hard wired "on" if the ignition is on. I would still think that the magneto should be able to charge the motor even at idle, even when small accessories are on.

Weird.

 

[RRitt]

Re: Charging voltage low on 1988 85hp?

I had placed it on a charger the night before for about 6 hours. However, I don't know how good / old this battery is. I think I'll charge it up and take it to be tested.

Another question... if the battery is removed from the motor while it is running, will the motor still run? It should, right? I wonder if this might be a good acid test to see if the magneto is working properly. I don't understand why the battery seemed to have drained so quickly. I did have to crank it for 30 seconds or so to get it to fire the first time yesterday, but after it was warm it started right up each time.

yes the motor will run but the voltage will be a series of spikes. The battery plays an important role in purifying your electricity for DC devices. It controls the cut-off voltage for diodes and prevents under-voltage. It absorbs the excess energy of stator output and prevents over-voltage. Without your battery the voltage is just a series of pulses running at same speed as engine. If you intend to keep your radio and fish-finder while also disconnecting battery then you MUST replace rectifier pack with a genuine voltage regulator like the one used in any old car. If you use a snow mobile regulator then try to get at least 25A rating.

 

[cambosoup99]

Re: Charging voltage low on 1988 85hp?

I would still think that the magneto should be able to charge the motor even at idle, even when small accessories are on.

Weird.

no, according to the factory service manual it only puts out a charge after you reach a certain rpm. below its not gonna put out. I'm not at home right now but when i get home i'll post what rpms it needs to be.

 

[pnwboat]

Re: Charging voltage low on 1988 85hp?

A series of video's showing the replacement/testing of the rectifiers on the Force motors and how the charging system operates at different RPM's.

http://www.youtube.com/watch?v=pAV14aj_DT0

http://www.youtube.com/watch?v=ThX0_E9x1mc

http://www.youtube.com/watch?v=R2ngCNezp8Q

 

[cstoaks]

Re: Charging voltage low on 1988 85hp?

Another good source for information on this subject would be the sticky on this forum http://forums.iboats.com/showthread.php?t=252684 I know that this seems to be the opposite of what you are experiencing, but many people in this forum talk about their charging rates at different RPMs. I just purchased and installed the voltage regulator on my motor to help with these kinds of issues.