Electrical System Problem

[skiguy]

At idle the alternator on my 2005 22v with Marine Power 340 doesn’t put out 13v. I have to rev up to about 1500 to get enough output. It’s a new 60amp alternator as well. I’m suspecting a ground or corrosion issue. I checked the battery leads and alternator leads and they seem free of corrosion. Does anyone have any suggestions? Where is the ground block on this boat?

Thanks!


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[chpthril]

Where are you measuring this sub 13V? Start here, and work backwards until you find the loss of voltage. Did you do a voltage drop test on those cables to determine no corrosion or just a visual? A voltage drop can find a bad cable that the naked eye cant see.

[skiguy]

Where are you measuring this sub 13V? Start here, and work backwards until you find the loss of voltage. Did you do a voltage drop test on those cables to determine no corrosion or just a visual? A voltage drop can find a bad cable that the naked eye cant see.

I tested at the battery only so far.


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[chpthril]

Why was the alternator changed? In a case like this, I immediately suspect the root issue is still present.

Id go right to the alternator output std, then the ring terminal, then starter, and so on. Since the alternator grounds to the block through its housing, then you would want to focus on the main ground at the engine block, and then again where it connects to the battery. Corrosion can grow and wick down inside the cable insulation, while the rest of the cable "looks" good on the outside.

[skiguy]

Why was the alternator changed? In a case like this, I immediately suspect the root issue is still present.

Id go right to the alternator output std, then the ring terminal, then starter, and so on. Since the alternator grounds to the block through its housing, then you would want to focus on the main ground at the engine block, and then again where it connects to the battery. Corrosion can grow and wick down inside the cable insulation, while the rest of the cable "looks" good on the outside.

The original alternator had a lot of corrosion and I noticed the same issue with low output at idle. I replaced it last season and then told myself it was a little better. Toward the end of this season I noticed my perfect pass display randomly acting weird while at idle. Something it had never done before. A look in the engine compartment showed I had a hose clamp break on the hose going into the engine block and it was spraying a strong misting stream of water across the back of the engine and surrounding area. I blamed the PP electrical problem I was experiencing on the water hitting the PP servo but I’m now not so sure.

You mention above the connections on the starter. The terminals on my starter are pretty rusty. I have noticed it slightly slower than normal to crank and it’s on the list to be fixed or replaced this winter. I discounted the corrosion on the starter as being my issue with low voltage from the alternator as I thought the starter is downstream from the battery and it’s corroded terminals shouldn’t affect the charging voltage going into the batteries, right?


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[chpthril]

Its very common for the alternator charge lead to route over to the starter, where it meets with the large main battery cable. Much shorter and easier, then running the alt cable to the switch or battery directly.

[Ronald Wiseman]

I have been battling with the same problem with my 2006 22v. I have managed to get it up to 13.7 volts at the cranking battery.
Since then once on the way I have noticed that the perfect pass also works way Better. What duel charging system do you have. What I had was an diode to prevent cross feeding and draining of the battery. If you have that diode thing check it. I had 1 volt drop just across the diode I replaced my diode with a new charge system with an different type. (No diode)

I’m still not completely happy with my charge rate as I also need around 1000 rpm to get the rate up to the 13.7volt rate on the house battery. I’m currently looking in to replacing my alternator to a 95amp unit. The reason for this is my charge range is good if I don’t use the stereo system. But once the amp draws current . The house battery only sees 12.1 volts.
Do you have a photo and the part number of the new Alternator you bought as I’m keen to get issue sorted but now I’m not sure if a new alternator will solve the problem.if you have a photo of the alternator this will also help too.

[chpthril]

An 06 with a Marine Power engine, already came with a 95A alternator.

If your house bank and cranking bank do not have the same voltage level with engine running, you have a cable or battery problem, not an alternator problem.

A .7+ volt drop across the diode osolator is normal for a diode, not a fault. Sounds like your 06V came equipped with the Tige EIDB system.

[skiguy]

I have the Blue Sea System Automatic Charging Relay (ACR) in my 22v. My issue is similar to yours, I need at least 1100 rpms to get my charge current to 13+ volts. I know for a fact I have corrosion issues where the alternator feed connects to the starter solenoid. Per Mike's advice I will inspect the cable ends and replace any corroded wire and connectors all the way back to the battery (and the solenoid too). One other thing to check is for corrosion or issues with cables/connectors at the ground block. I still need to locate it on my MP 340 (I believe it's somewhere on the engine block, right Mike?). A bad ground will cause all kinds of electrical problems.

From past experience the alternator should be able to provide 13v to the batteries at idle. Anything less indicates excessive draw by a device or resistance in the charging path (cables/connectors). On my boat the only accessories that run when the key is on is the ECM, depth finder and Perfect Pass (I use it as my speedo)... so not much draw and a normally functioning alternator should be able to feed these and 13v to the battery at idle speeds I would think.

I can't remember the exact model of alternator I used for my replacement. I think I ID'd the model # on the original and then did an internet search for a compatible replacement. The key thing is mine uses the two v-belts, so had to make sure the new one did that. You can go to marineenginedepot.com (Marine Power's parts site) and get the direct replacements there too.

[Ronald Wiseman]

Ok got to love Chpthrillhe was on the money with his advice!!!!
I pulled back the cover and did a few voltage drop tests. When it came to check the connection at the alternator it was noted that there was a hot connection. Fitted a new terminal to the cable and guess F28E889E-D6CE-40F1-B677-9E61904AB6DD.jpgwhat!!! Both battery where running with well over 13v. I will post a few pictures.

[Ronald Wiseman]

FFAD8706-747C-41B2-A09A-664FE909DFC9.jpg

[Ronald Wiseman]

Oh the test. Was done with the stereo at almost full volume

[Ronald Wiseman]

I still have a voltage issue at idle speed!!! Is in not possible to fit a smaller pull on the alternator to over come the low idle voltage problem???

[chpthril]

Easy answer is yes, you likely can put a smaller pulley on and increase the alt's RPM at idle. hard part, finding the right one. Will likely also require one size shorter belt.

[Ronald Wiseman]

Thought I would just share it here for future reference for others. My alternator part number is 8400111. This is the 95amp/hr unit fitted to mine. I will be ordering a new one and once here I will see if it is possible to reduce the size of the pulley on the alternator. I may just manufacture one in the lathe. Just because I can make it the exact size I need. 81CA113E-6436-497F-B337-8864C72A9CED.jpg