Finding a voltage drop?

[Romeyn]

I've searched this forum and read a few threads. There is a lot of general advice on tracing voltage drops! So that's not what I'm here for. I'm here in case, after I describe what's happening, someone knows and can tell me, "Oh yeah...that's really common on that boat/motor, here's what you do..."

I have a 1990 Four Winns 190 Freedom with a 4.3L V6 OMC I/O. It's been a great boat. This year I've had trouble starting it. The starter just seems..."weak" and it's honestly a gamble as to whether it will start at all. I started by assuming the battery needed to be topped up, so I put it on a charger. That worked once. I took the battery to my local auto parts store and they put it on a gizmo that charges it and then puts it under load. It would fully charge, but as soon as you took it off the charger you could watch the voltage drop FAST. It was new in 2017, so I figured I'd gotten my money's worth and bought a new one.

But that did not fix the problem. Brand new battery, fully charged and it was still like there was molasses in the system somewhere. I should say at this point that when I DO manage to get the boat started, it runs just fine. I next turned my sights to the alternator. I removed that and took that to be tested. I was told it was failing (though I am now skeptical of that) and replaced it too.

But THAT did not fix the problem. So I removed the starter (not fun!). I did not have a way to test it under load, but with 12v applied it takes right off like a starter should. There does not seem to be any issue with the solenoid either. I put it back. The problem persisted.

I managed to get it started one more time and was going to take it to the boat launch to trailer it (we are on a lake and the boat lives on a lift). Before doing that I took a friend for a ride. 3 minutes out from shore I glanced down at the dash and noticed that the NAV LTS toggle switch was on! I thought I had found the problem. That switch had been on for WEEKS and while tiny, that little incandescent bulb could explain the voltage issue! (Yeah yeah...I will replace it with an LED this Fall.)

But no. Same problem. 12+ volts at the battery. 13+ on the dash voltage gauge if I manage to get the motor started. But with the key on and the motor off, the gauge reads 10v if I'm lucky.

Help? Is this a "known thing"? I've taken the boat to my Boat Guy because I gave up. I suppose I could whip out my meter and start tracing things. But maybe someone will see this and tell me all I need to do is "change the spider gear in the muffler" or something and everything will be fine.

If you read all the way to the end, thank you!

 

[Lou C]

Ok I have a similar boat & used to have somewhat similar issues with the electrical system. To start with the battery cables were automotive grade junk so I replaced them with Ancor marine grade cable with clamps for the battery terminals instead of using wing nuts.
I also installed a dual battery system with 2 gp 27 dual purpose 650 amp batteries; my boat is on a mooring so 2 batteries is a must. Do not use wing nuts they loosen and result in high resistance connections causing voltage loss. Also the grounding point is a stud on the bellhousing that should be throughly cleaned up. I used heavier cables than the minimum (4 gauge commonly used), I used 2 gauge for the short runs and 1/0 for the long run from the port side battery to the switch.
Next you should take apart the big cannon connector (clamped to the shift bracket on top of the engine) & clean the terminals and sockets with contact cleaner. Look out for any burned terminals or wires. When re-assembling use a hose clamp to hold the 2 halves of that connector together. In the same area (shift bracket on engine) are 2 smaller rubber fuse holders, each has a 50 amp glass fuse; these should be checked for corrosion & oxidation. When re assembling these rubber connectors & fuse holders I like to seal the edges with dialectic grease to seal out moisture.

Next on to that old fuse box. Glass fuses? The tabs and fuses get oxidized and that can cause low voltage and intermittent problems. Clean the tabs and replace all the fuses; then spray with corrosion x or similar to keep off moisture. Ultimately it is best to replace that old fuse box with a modern Blue Seas box with blade type fuses.

Next, I found that somewhere in the harness feeding the fuse box there can be a bad splice which results in low voltage when you turn on the ignition. Ignition off I would have battery voltage there; turn the key to ignition and it would drop 1.5 volts. I tried adding a supplemental ground wire thinking maybe a bad return in the harness, no difference. So tried the same on the positive side and that was it. I ran a supplemental power feed (fused) running from the common terminal on the battery switch to the positive stud on the fuse box. That fixed the low voltage issue without tearing apart the whole 30+ year old harness. I used 8 gauge wire for this.

So that’s what I found with mine; this fall I am going to finally replace that old fuse box with a Blue Seas 12 circuit unit.
PS
When replacing starters & alternators I use ARCO marine units which have been consistently good quality. The newer style PMGR starters spin faster and draw much less current & are easier to install (lighter, smaller). When running you should always check battery charging voltage at the battery & not only rely on the dash gauge. You should see about 14.2v at the battery with the engine running at idle. On some OMCs you can have an overcharge condition due to high resistance in the alternator sense wiring. There is a work around for this too that I learned from Arco Marine. There is an even better way to wire the sense circuit that I can share if you are having a battery charging over voltage issue (like 15.5V).

 

[Bondo]

I've searched this forum and read a few threads. There is a lot of general advice on tracing voltage drops! So that's not what I'm here for. I'm here in case, after I describe what's happening, someone knows and can tell me, "Oh yeah...that's really common on that boat/motor, here's what you do..."

I have a 1990 Four Winns 190 Freedom with a 4.3L V6 OMC I/O. It's been a great boat. This year I've had trouble starting it. The starter just seems..."weak" and it's honestly a gamble as to whether it will start at all. I started by assuming the battery needed to be topped up, so I put it on a charger. That worked once. I took the battery to my local auto parts store and they put it on a gizmo that charges it and then puts it under load. It would fully charge, but as soon as you took it off the charger you could watch the voltage drop FAST. It was new in 2017, so I figured I'd gotten my money's worth and bought a new one.

But that did not fix the problem. Brand new battery, fully charged and it was still like there was molasses in the system somewhere. I should say at this point that when I DO manage to get the boat started, it runs just fine. I next turned my sights to the alternator. I removed that and took that to be tested. I was told it was failing (though I am now skeptical of that) and replaced it too.

But THAT did not fix the problem. So I removed the starter (not fun!). I did not have a way to test it under load, but with 12v applied it takes right off like a starter should. There does not seem to be any issue with the solenoid either. I put it back. The problem persisted.

I managed to get it started one more time and was going to take it to the boat launch to trailer it (we are on a lake and the boat lives on a lift). Before doing that I took a friend for a ride. 3 minutes out from shore I glanced down at the dash and noticed that the NAV LTS toggle switch was on! I thought I had found the problem. That switch had been on for WEEKS and while tiny, that little incandescent bulb could explain the voltage issue! (Yeah yeah...I will replace it with an LED this Fall.)

But no. Same problem. 12+ volts at the battery. 13+ on the dash voltage gauge if I manage to get the motor started. But with the key on and the motor off, the gauge reads 10v if I'm lucky.

Help? Is this a "known thing"? I've taken the boat to my Boat Guy because I gave up. I suppose I could whip out my meter and start tracing things. But maybe someone will see this and tell me all I need to do is "change the spider gear in the muffler" or something and everything will be fine.

If you read all the way to the end, thank you!

Ayuh,..... Welcome Aboard,........ Remove, 'n clean both ends of both battery cables will be a good start,.....

 

[cyclops222]

That new battery was RUN DOWN to almost DEAD !! 12. 2 volts is almost dead for power to start the engine !!
Take the battery out an fully recharge it with a 120 vac plug in wall charger. A GOOD charger. Recharge it at 5 amps. or close to it. A cheap or defective charger.......WILL NOT........do anything to spin the starter fast enough. After the charger ends the charging. Wait at least 6 hours for the voltage to FULLY settle down to.......12.5 or higher volts. 2 people needed. 1 on the starter key switch. Other...YOU... holding meter leads on the big parts of the cable clamps of the battery. SO you can see how much the battery voltage drops when person turns and holds key in STARTER POSITION for at least 2 seconds. Meter SHOULD NOT drop more than to 12.4 volts during cranking.
ALL new batteries need a FULL long term 5 amp. filling up recharge.
THat new battery MUST NOT be older than 6 months old. There is a date label on the battery somewhere.

 

[Romeyn]

Ayuh,..... Welcome Aboard,........ Remove, 'n clean both ends of both battery cables will be a good start,.....

So...I figured I should report back on my progress. My boat guy said it was new starter time. He had apparently applied power straight to it and it behaved the same way. I bought a new one, which was mercifully physically smaller than the original, and installed it. Same thing. Barely a crank, if it would at all.

So I dusted off my volt meter and braced myself for acting like I knew what I was doing and start tracing things. I started at the battery. I knew the positive cable was fine at both ends. But as I tugged on the positive/negative bundle as it left the battery and looped over the engine, there it was. I still can't believe it. The nut attaching the negative to the block was LOOSE! I have never seen that happen before! It didn't even occur to me to check.

I removed the nut, made sure everything was clean, and tightened it up. The motor started up like it was new.

I don't know whether to laugh in triumphant glory or cry.

Maybe I'll just put the boat back in the water and start enjoying the last couple of weeks of Summer. Yes, that seems like the thing to do!

 

[Lou C]

Now you got a spare starter, and more knowledge lol!
remember DC electricity must travel in a circle (circuit) from +--->-
anything that interrupts that, will cause problems.
On an old boat, with those glass fuses, beware the tabs that hold the fuses in and the fuses themselves, exposure to moisture will cause oxidation and things will quit working on you. At the start of each season take the fuses out one at a time and clean those tabs till they are nice n shiny, and replace the fuses if they are getting oxidized.

 

[Scott Danforth]

By cleaning the connections that Bondo referred to is using scotchbright pads or sand paper and cleaning the lugs, studs, and surfaces so clean and shiny that your mother in law would eat off them