Volvo Penta 4.3GL Alternator Problem?

[Arnoldsw]

I have a 2003 Monterey Montura LS 190 Bowrider with a Volvo Penta 4.3 L GL-A engine, sterndrive SX-M. It has an alternator with Vovlo part #3857561 (according to the online Volvo Penta store).

The other day, I noticed that the voltmeter on the dash was just above 12 volts (maybe 12.3) while the boat was running and in idle (around 600 rpms). The need of the voltmeter was also shaking quite a bit in idle. Reving up to higher rpms and in drive did not bring the need noticeably up. I have had the boat since 2006 and I never noticed the needle past 13 volts. I had it on and off a couple of times and it started right up - no problems. Reving up to higher RPMs in neutral did not bring it up either.

Today, I brought it home and put a digital voltmeter to the battery. When the engine is off, the voltmeter read around 12.65. With the key in the run position and the alarm sounding, it read around 11.77. With the engine running, it read around 13.77 - 13.80. The needle on the dash voltmeter read around 12.5.

I turned the boat off, cleaned all the batterry wires with a wire brush and cleaned the terminals with the brush. I fastened all nuts very tight. I also went under the dash and shook the wires around a bit (because I had a problem with the engine cutting out once due to some loose ignition wires). I rechecked the battery with my hanheld DVM (Digital Volmeter) with the engine off, with the key in the start position, and with the engine running and got the same results. This time, however, the shaking of the dash's voltmeter stopped and it hovered at 13. That's the value I have always seen since purchasing the boat and prior to this "shaking" and very low reading. Keep in mind that my DVM read 13.77 - 13.80. Maybe the shaking of the wires did something to stop the shaking but the dash's voltmeter is not reading what my DVM reads.

I took the battery out (a Walmart/Johnson Controls) 550 CCA (I think - whatever, it is rated higher than the Volvo recommended minimum) and had it tested. It is an August 2008 battery and it tested good. Just for kicks, I took a spare Interstate battery from 05/2006 that I had just charged and the test showed "marginal" on that one. That same battery showed marginal and that's why I bought a new one from Walmart in 08/2008.

I have been reading a lot of posts on alternator issues in this forum. Can someone tell me if the battery voltage is OK with what I wrote above about engine off, key in start, and engine running?

I am not handy at electronics and need to understand in detail how to check the alternator at the alternator. I have a DVM that shows Ohms and Volts. Where do I place the positive and negative leads to check the alternator at the source? Is 13.77 - 13.80 volts with the engine running OK at the battery? Again, the battery tested good, I have never charged it, and I have never had a problem starting the boat. It is just a very scary thing to see that Voltmeter in the dash shaking and so low.

 

[flargin]

Re: Volvo Penta 4.3GL Alternator Problem?

12.65, good
13.8, good
11.7, maybe a little low, but you did not say anything about it not starting, so I will assume it starts fine.

I would look at 2 things:

1. Is the belt to the alternator tight, if not is might slip when higer RPM than idle, and it might drop back to 12.65 v

2. keep searching for the loose connection, likely on the Ignition switch.... I also went under the dash and shook the wires around a bit (because I had a problem with the engine cutting out once due to some loose ignition wires)

don't just shake it, try to tighten down the connections, a loose connection could well result in the problems you indicate.

 

[Arnoldsw]

Re: Volvo Penta 4.3GL Alternator Problem?

The Alternator belt is tight. I had the compartment open and revving to 1500 or 1600 RPMs with no slippage. It also runs fine when in idle.

The boat had no problem starting three different times with the muffs on. I kept it running for a while too.

I will search for more bad connections under the dash.

Would a bad ignition connection cause the voltmeter to shake and give a readout that is almost 1 volt below what the battery output reads with a DVM? The needle only shakes when in idle. Maybe due to the vibration in idle???? I need to sea test it but the shaking and the very low readout seem to have been corrected, but the voltmeter still reads almost 1 full volt below the battery output when the engine is running.

 

[bruceb58]

Re: Volvo Penta 4.3GL Alternator Problem?

Does the shaking change when you speed the engine up?

13.8V is probably ok for the voltage output of your alternator. The problem is that it is reading the average voltage reading. Would be interesting to see what it reads on the AC scale. Should be 0.

Did you read the voltage right at the dash meter too?

 

[Arnoldsw]

Re: Volvo Penta 4.3GL Alternator Problem?

Prior to the changes made today, the voltmeter on the dash would only shake at idle speed. When I revved the engine up, the shaking would stop (but would still only read about 12.5). Now, at least with the muffs on and after shaking things up a bit, the voltmeter on the dash does not shake and now reads about 13volts (which is where it was from the day I bought this in 1996).

I have not tested the volts at the voltmeter. I cannot get to it without removing the casing under the dash. It looks like a pain.