Odd electrical problem on 1988 Force 50 HP- need expert help!

[sraley1053]

Just recently purchased a used boat (1988 Fisher Marsh Hawk, 16'). Has a known engine problem that I felt I could repair. At the start of troubleshooting discovered two trigger wires reversed based on wiring documentation found online. (later read that these are sometimes reversed OK). Switched the wires, cranked it, started right up! Wow, too easy.

Yes, for sure. She ran for about 3-5 minutes, idled nicely just before the blue smoke appeared from underneath the flywheel. I shut it down immediately, but of course not fast enough.

But here is the where the odd part starts. As I was standing there pondering what just happened, switch off, nothing moving, I hear a pop and then comes the sizzle with another cloud of smoke this time the integrated CDI coil packs. It seems power got to all the electrical components except the trigger and the rectifier (both checked OK).

I triple checked everything for possible shorts and see nothing. I located a set of replacement stator and both CDI packs; not cheap. I installed those cautiously and again checked for shorts al along the way. All seemed to check out to the specs.

Tried to crank it up... first of all no spark, either cylinder. Again, while pondering the situation, pop-sizzle, at least one CDi fried again with switch off. Is it possible the recitifier checks OK, but is not OK. Or are there other experiences with these Force engines or Fisher boats that someone could share? Thanks in advance!

 

[pnwboat]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

Sounds like something is not wired right. I would suspect that the previous owner may have messed with the wiring. Sounds like there may be 12 volts constantly going to the CD modules. There should be no 12 volts on any of the connections going to the CD modules. The CD modules are designed to operate off of AC voltage generated by the stator. In fact, the ignition system is self energizing, so you don't even need 12 volts for the ignition system to work. You can pull start the motor with a rope without a battery connected and it'll run just fine. Check the connection on the terminal block that has the white wires from the CD modules connected to them. This is the ignition kill circuit. There should be no voltage on these terminals. If there is, then the white wires are either connected to the wrong position on the terminal block or something in the wiring harness is wired wrong. Maybe ignition switch?

 

[sraley1053]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

Thanks for the response. I understand that 12V should never be on the ignition side, so I have really tried to check this thoroughly and can never get a reading of voltage on any of these terminals. It seems it is an intermittant situation that pops up randomly. I have not considered the switch but maybe I should give that some attention. Do you have any troubleshooting guides for that?

Also, I was not sure if a rectifier could bench test OK but have an intermittant failure.

 

[pnwboat]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

I've never seen a rectifier that was intermittent. Not to say that it's not possible but I would say that it's very unlikely. If you have any doubts, you can get a replacement 25A full bridge rectifier at Radio Shack for less than $5. I guess it's possible that if the rectifier is shorted, it may back feed DC voltage to the stator and induce DC voltage to the CD modules. I do know that a shorted rectifier can affect/interfere with the ignition system.

 

[sraley1053]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

OK, for $5 I will go ahead and do it. I was wondering if there was anything special about these bridges or if a standard from Radio Shack would work. Good to know! Thanks.

I agree with you though it is probably not that. How about testing the switch. Any advice or procedures on that?

 

[pnwboat]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

Nothing unusual with the rectifier. Just a standard full wave bridge rectifier. Typical output of the stator on your motor is about 9 amps, so this rectifier will work just fine.

http://www.radioshack.com/product/index.jsp?productId=2062584

I'm probably stating the obvious to you but just to make sure......The two stator wires should connect to the terminals marked with the " ~ " symbols, 12 volt battery connection, usually the red wire should go to the terminal marked " + ". The Negative terminal " - " should connect to the block or ground.

As far as the switch, I'd start out by a close inspection of it and the wiring making sure you don't have possible shorts between terminals, you know anything obvious.

 

[sraley1053]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

Yes that all checks out on the rectifier. Thanks!

Here is another thing I noticed after installing the new ignition.... wheras the electric choke was functioning during the short 3 minute initial trial run... it was not functioning after the new ignition was on. Is this controlled by temperature? It was rather hot yesterday when I was trying to start it; would 90 degree air temperature stop the choke from activating or this perhaps another symtom to the real problem?

 

[Frank Acampora]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

The switch is (or should be) a standard six pole push to choke. To check it you use a VOM on the terminals. The two "M" terminals should have continuity with the switch off and infinite resistance with the switch on. This is the kill circuit and with the switch off it grounds the CD capacitors to prevent them from dumping voltage into the coils. Thus: no spark.

The "I" terminal should have continuity (or show 12 volts) with the "B" terminal only when the switch is on or in start. This powers accessories.

The "S" terminal should show continuity with the "B" terminal only with the key in the start position.

The "C" terminal should only have continuity with the "B" terminal only when the key is pushed in and held.

Battery (red wire) Should be wired to the "B" terminal. White to one "M", blue to the other "M", yellow to "S", and green to "C".

Red should NEVER show any connection to an "M" terminal.

Internally the switch is a fiber disc with copper segments (like a printed circuit board) that are contacted at various positions. They are relatively trouble free and usually fail by losing contact. BUT: If a segment has come loose and shifted it could intermittently short the wrong terminals. The switches are assembled either with a metal case and prongs or a plastic snap together case. With either it is possible to remove the back and check the switch internally but with a new one costing only 17-25 bucks, why bother?

 

[sraley1053]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

Great info! Thanks.

I will give it a going over tonight and see what I find.

So, is the "C" terminal for the choke energizer? If so the failing choke seems to tie in.

 

[sraley1053]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

Sorry for the delay, had a few real life interruptions. Again, great advice... the switch showed connectivity between the "B" and and one of the "M" terminals. Ordered a switch... will update on results later. Thanks!

 

[sraley1053]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

OK, finally got back to work on the boat. Purchased and received a new ignition switch. All seems to test out with the meter as you describe EXCEPT... where you say "The two "M" terminals should have continuity with the switch off and infinite resistance with the switch on. " I measure .432 K-ohm with the switch on and all connections (switch installed). Is this an acceptable value? Or should it be higher?

If so, what should I check next?

P.S.: I did mean to mention that I found a small fracture piece of plastic inside the switch. I can tell it has been broken for a while because the fractured area is grease covered from the electrical grease in the switch. I suspect this was getting into the metal disk of the switch and causing the intermittent short. Thanks for pointing me to the switch.

 

[sraley1053]

Re: Odd electrical problem on 1988 Force 50 HP- need expert help!

OK, after a long delay, finally able to get back to work on the boat. To recap... I think the switch was allowing 12V on the ignition side which was my root problem.... burned up the stator and both CD coils. I have replaced the switch, stator (used), and one CD coil (used). The stator ohm tested good. It is the CDI brand with four leads instead of 2. The seller suggested that I use only leads 1 and 2 and tie-up 3 and 4 securely; CDI instructions say use all 4 leads. So that is my first question- use both brown-yellow together and brown-blue... or just the 1 of each color. Secondly, the CD coil looks good physically, but is there anyway to tell if it is really good other than installing and checking for fire? Since he only had 1, is it safe to test fire the engine with only 1 CD coil connected? These seem to be hard to find.... I am currently watching eBay for a second coil pack; any other leads for a used one would be appreciated. Thanks in advance for any advice you may have!