Starter or Battery Problem?.. Help Needed Again

[bobk]

Engines are 6V92's 425 HP on a 1981 48MY. About a month ago I started noticing a larger voltage drop when starting the starboard engine, and sometimes a real slow cranking. I assumed the 8D's were loosing it again, but they are not yet three years old. Furthermore two 8D's are wired in paralled on this engine to serve it and the 12.5 Westerbeke. Battery water levels are OK and specific gravity on each cell was normal and uniform.

I had a mechanic do a load test and he found the batteries were fine. He also tested from the battery to the starter and it still looked good, but found when starting, voltage dropped to 5-8 volts at the battery. Paralleling the other 8D in did not help. After three or four test starts, the starter didn't turn over the engine. My mech felt the various connections and didn't find any that were warm.

The mech pulled the starter and I took it to P&H Automotive who checked it and found it was fine. They did a PM job on it for $135. The technician found no evidence (discoloration) of having pulled a heavy amp load. Any thoughts on where else to look before the starter is installed?

Bobk
Chateau de Mer

[Boatsb]

Ground. That is where I see a lot of people miss the boat ( pun intended ) when it comes to troubleshooting.

[Seabrooke]

Ground. That is where I see a lot of people miss the boat ( pun intended ) when it comes to troubleshooting.

G'day Bob,

I agree with Scott.

Poor ground (or earth - depnding on the terminology that you are used to) is most likely to be the cause of the big drain and poor cranking.

Recently I could not get my engine to turn over fast enough to start for love nor money. The battery was absolutely fully charged and the engine was fine.

When I eventually checked - and sorted - the earth connection (check any and all) it turned over like a beauty and fired instantly.

Most problems that seem mysterious have simple solutions.

Hope this helps.

[Canuck Dennis]

I had same issue with generator....click..click...fixed the ground and whir whirrrrrrrrrrr...

[Boatsb]

The other issue could have been a hung brush but if it was gone over that would have been fixed already.

[MikeP]

Basically after his battery test, the voltage drop test proved it was a wiring issue. There was no reason to pull the starter. Connections/wiring that aren't passing current won't get warm because there is insufficient current to make them warm. A cable could be bad somewhere internally anywhere along it's run. But I agree that the grounds are the first thing to check.

[daniel r morrison]

I would try cleaning the battery posts. what bothers me is why the voltage at the battery dropped so low. without a ground there would be no current flow and no load on the battery. high resistance in the circuit could be enough to block voltage and result in the same no load cituiation on the battery. a battery with no load should read 12.6+- volts. Did the mechanic test voltage on the actual battery posts or on the wire terminals connected to the posts. I had a similar problem where 6" of wire at the starter connection had corroded internally, ( actually turned an orange color). When I tried to crank the engine the voltage at the starter terminal went to 0 but remained high at the battery. under no load the voltage at the starter terminal was the same as the battery.

[Kim Beatley]

Interesting, something must be in the water!!! I just had (and still have) the same problem..... Good battery test, but no crank on the other end. Thanks for the tips. Will start working connections and grounds on Saturday.

[krush]

Define PM job on the starter. ASSUMING everything else is correct (wiring, etc), it is possible that the starter is toast but looks fine on the bench because they just run it without a load.

I just replaced an outboard starter that sounded fine on the bench but it wouldn't crank over the motor and drew tons of current and got the wires hot, etc. First I thought it was batter connections, then battery. It was the starter....

[MikeP]

The purpose of a voltage drop test is to check the wiring/connections. If the voltage drop was as described, then the wiring/connections are faulty or the wire gauge size is too small for the application. Of course, that doesn't mean the starter can't also be a problem - which could have been caused by the low voltage. But the V drop test is the first thing to do and the wiring the first thing to correct.