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7.5HP 4 Stroke Honda BF75 No Spark

D

dam123

New member
Hi guys, I recently purchased a 4 Stroke 7.5HP Honda outboard engine without and handle and I've not had any luck with starting it. I get fuel at the spark plugs as normal but no spark what so ever. I'm new to outboards so I don't know a lot about them. Is there any chance that I can bypass the start button on the handle (if there is one) and start it. I hope to resolve this issue by the end of next week because I'm going on a camping trip and I need an outboard engine.Any help is much appreciated.


Thanks
 
That's probably a stop button not a start button.
You can disconnect it if you think that's the problem.
The spark on those can be very difficult to see.
Best to try it in low or no light.
 
Agree completely with alumarine. No start button.....only stop button. The button is used to GROUND OUT the coil under the flywheel that feeds the ignition coil voltage. Make sure that wire isn't grounded.
He is also correct about how faint the spark is. Try pulling over engine in the dark to verify no spark.
Many of these older models will have a "neutral start switch" mounted on the shaft that is connected to the shift lever. It is located on that shaft just inside the oil case on the starboard side of the outboard. Those go bad or get out of adjustment and won't allow spark.
Do you have a voltmeter and know how to use it? That can help alot when figuring out a no spark condition.
 
I have a similar issue, but was able to muster a weak spark after replacing the condenser with one I had to hawk to stay in place. The plastic section of the points that touches the cam is visibly worn and Im trying to get a set of points. The condenser is NLA, only one for sale on ebay as a part of a tuneup kit for a mere $150 and a used one for $22
 
The lighting coil is producing 1.5 to 2.4 volts and the green light barely lights up when grounding the oil sensor wire. I hereby summon a good samaritan to tell us what the output voltage of the lighting coil should be, as well as the Ohms of resistance it should have when probed with a multimeter. With the meter set at 200 ohms, it showed 26.2 ohms. The charging coil is kaput, open circuit, but I believe it has no part on the ignition workings. Im all ears for your input.
 
Yeah,
$150 is pretty steep for a set of points!

One thing you might try, if the point faces you have aren't pitted and have good contact, would be to use a quality 2 part epoxy to build up the cam rider a bit or attach a phenolic tip to the stub. Might work for a while.

BTW...gap is 0.012" to "0.016".

It used to be that if you went to a Napa store on a Wednesday (slow day) and asked nice, ( I wouldn't use the phrase "I summon" as you did here) someone could try to match up the points you have from inventory. But I'm not sure they even stock breaker points anymore these days. But I bet Echlin still makes them for old cars.

The "lighting" (primary) coil resistance is listed as 2.0 ohms

The condenser capacitor value as 0.24 mfd.

There is a hand written note in a shop manual I bought used that says a Borg Warner G610 capacitor will fit but I have never tried one so take that with a grain of salt.

I don't know what the start volts should be for the primary coil. It is rpm dependent and will vary. I believe it can get up well over 50 volts ac while running but not positive. Haven't worked on one of these in years and no notes on that.

The permanent magnets in the flywheel can de-laminate and weaken volts. Rust building up on the coil ends and magnets can weaken volts as well. All you can do there is remove the flywheel and inspect, clean or replace.

You are correct that the charging system has no bearing on the ignition system or oil lamp operation.
But, you can get the coil rewound if you're interested in restoration so don't throw it away or pick at it. A rewinder will need it for the core and to count the turns plus wire size.

Hope this helps some.
Good luck.
 
Thanks a lot J,
I bought points for a Honda CT90 and only used the rocking arm to refresh my points. I also replaced the condenser with one for a Toyota Hilux that has 25 microfarads. (I had to cut the condenser bracket and epoxy it to the rear of the condenser. Other condenser from a Honda CB750 I ran across with a rear bracket was too tall and the spark advance hardware on the timing sprocket would strike it. In addition, I replaced the spark generator with one for a Honda generator. Now I have a much better spark, no need to turn the lights off to see it. The spark generator I used perfectly fits in the original 74mm mounting holes, but only has one wire so I lost the green light and the oil warning. However, I'm hunting for a charge generator and should be able to rewire the light and recover the battery charging abilities in the process. I got these parts from Ali Express, very inexpensively. Hope that helps someone in need.
 
 
 
smoothbf75 said:
ignition coil, with condenser attached, may work. The one I installed does not have the condenser. I'll order this one and report, as it is similarly priced as the condenser.
Click to expand...
smoothbf75 said:
Looking at it it wont work, as the spark plug wire comes right out of it. do not order this one, order the one I
Click to expand...
 
I've been looking for another condenser, as I think the condenser does not necessarily has to be under the timing pulley. I think a condenser mounted externally should work, as long as it is connected in the original place, together with the points and its wire is long enough or extended to the new mounting location. There is space to route the wire out of the pulley, through the same hole that the wire from the lighting coil enters the ignition plate.
 
This is the one I used, but in order to fit it inside the plate, I had to remove the bracket, which left it with little holes that I had to fill with epoxy. This one is a good candidate for external mounting, as it has a fairly long wire.
 
looked at the original lighting coil, removed the tape. The coil looks good, no black spots, has continuity with a resistance of 176 ohms. Wrapped it back up. Jgmo mentioned 2 ohms being the nominal value, connectors don't make easy contact to the multimeter probes, had to wiggle them into moving the needle. This could be wire/connector related.
 
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