2005 Switch 20v Alternator

[girthquake99]

I have a 2005 Switch 20v and have noticed that my batteries are toast after a day or two on the water. I charge them for each trip but am wondering if they are not getting a charge. My voltage regulator is constantly at around 12.3 volts and never goes higher. This weekend I plan to do a metered test on the alternator but if it is bad and needs to be replaced, I want to get a head start on finding one. The part numbers I have from old manuals do not match anything out there now. Has anyone had any luck located an alternator for the Marine Power 5.7 vortec engine? Thanks in advance for your advice.
Josh

[chpthril]

My voltage regulator is constantly at around 12.3 volts and never goes higher.

This is battery voltage, not alternator output voltage.

[girthquake99]

Sorry, I meant to say my voltage gauge on my instrument panel, not regulator. No idea why I said that!
I did get a response from Marine Power regarding the part number. They recommend this one:
https://marineenginedepot.com/altern...-belt-delco-oe

[Ronald]

I have. 2006 22v. I have had low voltage on the cluster volt meter since I have had the boat and for years now have been chasing this gremlin. To date I have noticed and done the following.
1: I had a 1volt drop between what is at the battery and what is reflected on the cluster volt meter, so I would check at the battery and then compare to what you have under the dash at the volt meter.

2: my boat had a diode between the main and house battery that I notice had a voltage drop. So for this reason I replaced it with a Alturnative duel battery charging system. This works well

3: I have replaced both batteries (I would say that was due to the age and required replacement.) and not related to the low voltage

4: over the years the alternator eventually gave up so this was replaced.

5: After doing all of the above there has been a dramatic improvement and was runs as high as 13.8 volts at rpm over 1000. As the alternator is new it can’t be the voltage regulator as this is built into the alternator.

6: as the voltage then seemed to improve with engine speed. I then measured pulley size and did a few calculations. I machine up a smaller pull for the alternator. This has improved the low voltage issue but still hunting 50rpm to have it run above 13 volts at low idle. My boats low idle runs at just over 700 rpm’s. And now I’m getting 14volts on the volt meter at high run speeds.

7: I have now also noticed a post here that show how to calibrate the potentiometer on the fly by wire system.
And also a wiring change whereby the voltage for the potentiometer is wired to the ECM rather than taken from under the dash. This is so the ECM and fly by wire/ tige speed set sees the same voltage. This I haven’t done yet but have a feel this will resolve my low voltage idle issue.

hope the above helps you and I have one question. Has anyone implemented item 7 and has it been successful. The reason I ask is I’m not one that is in favor of changing wiring on the ECM of my boat. And with what I currently have my boat is usable.

Thank

[Ronald]

I have. 2006 22v. I have had low voltage on the cluster volt meter since I have had the boat and for years now have been chasing this gremlin. To date I have noticed and done the following.
1: I had a 1volt drop between what is at the battery and what is reflected on the cluster volt meter, so I would check at the battery and then compare to what you have under the dash at the volt meter.

2: my boat had a diode between the main and house battery that I notice had a voltage drop. So for this reason I replaced it with a Alturnative duel battery charging system. This works well

3: I have replaced both batteries (I would say that was due to the age and required replacement.) and not related to the low voltage

4: over the years the alternator eventually gave up so this was replaced.

5: After doing all of the above there has been a dramatic improvement and was runs as high as 13.8 volts at rpm over 1000. As the alternator is new it can’t be the voltage regulator as this is built into the alternator.

6: as the voltage then seemed to improve with engine speed. I then measured pulley size and did a few calculations. I machine up a smaller pull for the alternator. This has improved the low voltage issue but still hunting 50rpm to have it run above 13 volts at low idle. My boats low idle runs at just over 700 rpm’s. And now I’m getting 14volts on the volt meter at high run speeds.

7: I have now also noticed a post here that show how to calibrate the potentiometer on the fly by wire system.
And also a wiring change whereby the voltage for the potentiometer is wired to the ECM rather than taken from under the dash. This is so the ECM and fly by wire/ tige speed set sees the same voltage. This I haven’t done yet but have a feel this will resolve my low voltage idle issue.

hope the above helps you and I have one question. Has anyone implemented item 7 and has it been successful. The reason I ask is I’m not one that is in favor of changing wiring on the ECM of my boat. And with what I currently have my boat is usable.

Thank

[chpthril]

The solution to a voltage drop is never to produce more voltage, but to resolve the source of the drop. So a new pulley that increased the alternator's RMP is a bandaid.

As to an ECM code 81. A low voltage reading on the dash and a false code 81 had nothing to do with each other.

[Ronald]

The solution to a voltage is never to produce more voltage, but to resolve the source of the drop. So a new pulley that increased the alternator's RMP is a bandaid.

As to an ECM code 81. A low voltage reading on the dash and a false code 81 had nothing to do with each other.

I couldn’t agree more with your comment. However the voltage regulator should take care of any over voltage situation. And secondly looking at the alternator speed at max engine speed I was well within range of what the alternator max speed after the changes had been done. I have spent hr reading up on the current low voltage issue on the 22v, 24v/ve and to me it looks like it’s a very common issue. Voltage drop could be anything from a bad ground, poor connections or even incorrect cable sizing. Maybe another solution would be to up size cables from the battery to the dash and I’m sure the fresh cables would help.
at the end of the day my boat has never run as good as she is now. The. Low voltage also use to effect the tige speed set. This problem has also been solved since the voltage is running in the correct range under the dash. The following stands to be corrected as I don’t have a good diagram but I have note the following:

I have also considered up sizing the cable but I have noticed that there is more the one supply from the back of the boat. The supply to the buzz bars +\_ have some good size cables and the correct voltage I have always noted on the buzz bars under the dash. If I under stand it the light, ballast is taken from the buzz bar The problem lies with the purple supply that runs the instrumentation cruise control and fly by wired circuit.

CHTHRIL please correct me if the above is incorrect. Secondly please note that I respect your input as I know you have knowledge of the tige boat.

[chpthril]

However the voltage regulator should take care of any over voltage situation

Lets first clarify a couple things. Low system voltage is an alternator output issue.

A voltage drop is were on one side of a termination there is proper system voltage and the output side of said termination there is a drop in voltage.

Both of these have a different fix.

A properly working regulator is to, well, regulate the voltage in the desired range. However, even a working regulator can go open-field if the battery is suddenly isolated from the alternator. Turning the battery switch to OFF or disconnecting a battery cable while the engine is running. However, a voltage regulator cannot compensate for a bad/poor connection that results in a voltage drop at a helm gauge or fuse/breaker panel. The regulator only reacts to a load from a low battery or amperage consuming device.

the code 81, from my understanding, was that because the ECM had two different voltage sources it monitored. One was a more direct path. The 2nd was indirect. Once that 2nd source passed through a couple of terminations, it resulted in a slight voltage drop. This caused the ECM to set a false 81. So the fix was to split the direct voltage path 1 to then supply path 2, eliminating the voltage drop.

The speed-set could suffer from both the above issues = low system voltage or voltage drop. But as noted, the fix is different for these.

So, if the system voltage, as in whats coming out of the alternator, is within a proper and acceptable range, and the downstream electrical issue is because that proper system voltage is lost somewhere along the way, then a smaller pulley to increase alternator speed is not a needed resolution.

other than the code 81 on an 06 Marine Power fitted Tige, all of this is basic charging that applies to just about any boat or car.

Ive spent decades watching supposedly experienced mechanics chase and try to fix a symptom, not the root cause of said symptom. My takeaway from your post was a voltage drop causing issue and the fix was to increase the alternator output with a smaller pulley. Any increase to the alternator's output voltage will trickle over to the downstream system, but the original voltage drop is still there, its just masked now.