Bad Engine Ground?

[Danno1966]

History...
98 Mercruiser B3 set up in a 27 foot Crownline Cabin Cruiser.

A while back I noticed a squeaking/chirping coming from the alternator. At about the same time I noticed that the voltage was elevated to around 15v while cruising. The batteries had recently been run dead when I left the fridge on DC and the dock lost power. Since the batteries were now 8 years old, I got new Deep cycle batteries and replaced the alternator. Squeek was gone, but voltage was still high.
Then once in a while I would get ticking from the starter, which got worse over a few months. I then cleaned up some old wiring where there was some corrosion starting to set in. When I cleaned up the negative cable from the engine ground, all symptoms went away, and she started strong and voltage was good. That lasted about a day. The starter ticking and even some grinding came back So I had a mechanic change the starter. Symptoms didn't change except the high voltage is better.
Now, I can see the engine ground where the cable connects at the back of the engine (really tough to get to though...), and it's has some rust and corrosion.
COULD THIS BE THE ISSUE? the boat runs perfect except for the ticking in the starter.
Along with the ticking, when starting, the guages jump around, and the cabin lights dim significantly, which it never did until the ticking showed up.
Could this be a corroded engine ground?
Help me out! Thanks!
-Dan

 

[Chris1956]

The main grounds do rust because of the block being made of cast iron. Unbolt the ground and file the mating area clean. While you are at it, you might add some additional grounds to the main ground and run them to the starter and alternator.

 

[Danno1966]

The main grounds do rust because of the block being made of cast iron. Unbolt the ground and file the mating area clean. While you are at it, you might add some additional grounds to the main ground and run them to the starter and alternator.

Because the back of the block is so difficult to get to, why can't I move it? Does it have to be there? Do my symptoms sound like this could be the culprit?

 

[airshot]

Once thoroughly cleaned to brite and shiny, coat with a sticky grease to slow down the rust and be sure connection is really tight.

 

[ESGWheel]

Do my symptoms sound like this could be the culprit?

Yes. Bad connections can cause lots of issues including the symptoms you are seeing. Corrosion can also occur on the POS side as well, so be sure to clean up both, not just the neg. This does mean disconnecting the connection and cleaning to bright / shinny where the matting occurs as Chris and Airshot state.

Because the back of the block is so difficult to get to, why can't I move it? Does it have to be there?

Short answer: No, ie can be moved. Longer answer: Does not matter where the engine block ground is (front or back) if it’s a point that makes sense > this means a bolt that threads directly into the block that holds the cable; do not put the cable on top of say a bracket. And need to be cognizant of the cable run to not interfere with things like belts or be too close to the exhaust.

For that suggested extra ground wire to your alternator here is an idea: get your connections as they currently exist cleaned up to get you back and running with some confidence for the rest of the season. But also measure out and determine what is needed to replace both the POS and NEG (with extra wire to the alternator) and order up some proper tinned (aka marine) cables from a place like this link.

That way you can replace at your convince and be secure knowing you have now provided a longer term solution. Still need to do annual checks and maintenance as needed but you will have a good foundation.

 

[cyclops222]

When you are cleaning cable ends ? Also check where the copper strands go under the insulation !! I find corrosion eating up the copper strands under the insulation ends. Would need a new cable a few inches longer to make replacement easier ?

 

[Danno1966]

I have one more question....or two.
I am somewhat confident a bad engine ground is my problem.
Aside from changing the ground cable, is there a way to test this to validate?
Next, would adding a ground cable suffice or does the primary need to be replaced?

 

[ESGWheel]

Glad you had some good runs. Is there anything you have done to address your issue? Please confirm yes or no as it will matter for follow on troubleshooting.

You can try to test the resistance between the neg battery post and a good clean (bare metal) part of the engine block. But I suspect it will be inconclusive as this seems to be an intermittent problem. In other words, if it’s good, then what? But give it a shot anyway.

You can run another neg battery cable to a different spot on the block since the cable at the battery end is on the stud vs. the post i.e., you can dogpile other connections on the battery stud but just make sure all clean and bright and put the new one on the bottom.

But longer term I would do what is suggested in post no. 5.

 

[Bt Doctur]

Most issues are caused by the steel ends crimped on the cables instead of copper ones. Also the ends of the cable where its crimped are usually black from corrosion. Cutting back to clean copper and recrimping copper connectors solve the voltage problem

 

[ESGWheel]

If you do decide to cut and crimp, please research this toughly as it takes special tools (like this link). Frankly for me, I am always looking for an excuse to add to my tool collection. So, this could be a good one but probably not used that frequently; I have used my batt cable crimper perhaps 3 times in the past 8 years. Post any questions you have about crimping after looking up the how to’s if you go this route.

 

[Danno1966]

Great information from everyone! These are some of the best responses I've ever gotten to a problem. Thanks you!!!

I did ad a ground cable as a last minute impromptu thi g to try, which seemed to help, but I attached it to a bracket, so I'm going to find a better spot on the block.
Then follow some of the longer term solution suggestions from your responses.
At the same time all these electrical issues were arising, my TPS went bad, making it almost seem like the issues were related. So I've been doing a tune up, IAC and TPS making a world of difference. I still get a slight ticking when starting, and I am confident a new ground may just be the solution.

Thanks again! I sincerely appreciate the quality advice!!!

Dan