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2004 bf40 intermittant starter problem

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Onetoomanychucks

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I have an '04 bf40 with very little use, about 450 total hours. The starter fails to turn the engine over every so often, especially after repeated cranking. It engages with the flywheel, but then just hums. I took the starter apart and checked the armature and brushes, it looks brand new inside, no obvious problems with continuity or worn parts. I'll probably change the relay next, but I hate to just start throwing parts at it. Battery is good. Anybody have an opinion on what I should try next? Thanks.
 
Docksidemarineservices said:
If the starter gear is not retracting back into the starter and staying engaged with the flywheel, it will not spin the engine over.
Click to expand...
The gear retracts when key is released like it's supposed to, it just acts like it would if the engine was seized, engaged and drawing amperage (humming) and not turning over. The engine can be turned by hand at the flywheel pretty easily. The battery is new. It runs fine when it starts and only seems to happen after longer periods of cranking, and not all the time.
 
Long periods of cranking??? Is this engine hard to start? Or, did you mean you do a lot of "gun and run" boating with FREQUENT starts?

BIG difference.

If it is the long crank times, then you need to find what's up with the tune on the engine. These should fire, pretty consistently, in a revolution or so.

If it's frequent cranking, then you are probably looking at a poor connection somewhere in the system that heats up with each attempt and eventually builds up enough resistance to current flow that you are getting the no crank condition.

"THE BATTERY IS NEW"...Was it replaced to solve this problem? I can't even count how many bad "new" batteries I've been burned by over the years. If the problem started occurring after the battery was replaced then it is suspect. New or not. Take your battery voltage measurement AT THE POSTS before and after cranking. If you have help, you can also get some good info by taking the battery voltage while the engine is cranking. You should have around 12.6 volts before cranking.....over 10.5 volts during cranking.......and no less than 13.6 volts charging voltage after the engine fires.

I also like to disable the ignition and crank for 10 seconds and see what AT REST battery voltage is after cranking.
With a healthy battery...if it starts off at 12.6 volts...it should not fall more than a couple of tenths....12.4 volts I would consider ok. It's a "poor man's" load test.

This is a good time for you to Google "Voltage drop testing". Volt drop testing is THE prescribed method for finding excessive resistance in connections and components (cables) EASILY and RELIABLY. There are several good tutorials about what it is and how to do it using a decent DMM.

If drop testing taxes your brain or isn't in your future for some reason then all I could offer would be to go over each and every connection....ESPECIALLY ground connections....and take them apart and clean them until SHINY. BOTH SIDES! Corroded connections will be accountable for well over half of all boating electrical faults.

This may include battery cable connections at the battery AND the boat/outboard. Battery 1-2-ALL selector switch. And the mounting surfaces of the starter since I believe on this outboard it grounds through the engine block.

If you know how to "hot jump" your starter to get it to crank, do that the next time it fails to determine if the problem is in the high current side of the system or the control side. If it "hot jumps" easily, then you may be on the right track looking at the relay.

I will be interested to see what you find so don't hesitate to ask more questions if you need to.

Good luck.
 
Thanks for the reply jgmo. I'll give some more details.
First, the boat gets very little use, maybe three trips a season. It has no running issues, and usually starts very quickly, within a few revolutions. The problem first started last spring after it had been sitting for the winter. I usually drain the carbs when I know it will be sitting a while and when winterizing. The long cranking periods were only at first start up after winter getting gas to all the carbs and on a couple of very cold mornings.
The batteries were six or seven years old and I made the assumption that sitting over the winter might have done them in. I got new batteries, but the problem still happened when switched to either one. I only used the boat one other time during the summer, but since it was warm, the boat would start normally on only a couple of cranks.
Getting it ready this week, I decided to crank on it before putting gas in it to see if it would act up. After four or five cranks of maybe ten seconds, it started to hesitate and couldn't turn the motor over. It also heated the grounding wire from the midsection to the transom bracket, so evidently that current can't get back to ground the way it should. I'll get to work later this week and check the connections under load and try to find the problem. Thanks
 
It sounds like you do pretty much everything right. I commend you on draining your carbs as you do. BIG ADVANTAGE over those that don't.

Yes, heat is the dead giveaway that resistance is building. The wonderful thing about voltage drop testing is that you can identify a bad cable with the technique. Before volt drop testing was developed, the only other way to do that was to actually strip off the insulation and look for corrosion and broken wire strands. So, you might as well have just pulled the cable and replaced it in a sort of hunt and peck manor.

If you are familiar with VDT, then you know it works. If not....you will soon see how effective it is at finding high resistance in wiring. In most instances, it is very easy to do if you have a helper. As long as the connections you want to look at are accessible, it is one of the easiest tests there are for troubleshooting.

Placing your meter probes on the terminal ends of that section of ground cable while the starter is engaged may reveal a high reading. If so, you have found the problem and you will know that the cable needs to be replaced.

The ONLY thing that should drop more than about .250 volts (1/4 of one volt) in that circuit is the starter motor itself. It is the dedicated load and it should (ideally) drop ALL the available voltage.

Make sure you pay attention to battery voltage as you test. It will fall the more you crank and it may be necessary to charge the battery if the "at rest" voltage falls below 12.4 volts. You will not get reliable test results unless the battery is fully charged.

Good luck.
 
Started checking voltage on the ground side of the starter and I found the negative battery cable from the motor was crimped between the battery compartment and the side of the boat. Vibration over time cut into the insulation, so it was basically grounded to the hull. Works like champ now. Thanks for the advice.
 
I'm assuming it's an aluminum hull since just about every other material they make "small" boats out of would likely be non conductive.

Haven't seen that one before and good job on tracking it down.

You may have gotten really lucky in that, with a good amount of current flow at the break in the insulation, localized heating could have damaged your hull.

Thanks for the update and congratulations on getting it fixed.
 
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