Johnson outboard trouble

[okeedokee]

Hello guys (and girls). I am in need of a little advice.
I bought my first boat last week, after a few years of borrowing my friends. It's only for fishing so I got a little 17ft Microplus.
The guy who sold it to me has stated that the engine has had a good service and was running fine.
So my first fishing trip! Everything started well. Boat launched easy, motor running and heading out to sea. After about an hour of running the engine just stopped. It was like I had hit the kill switch (I don't know if the engine has such a thing). So first thing I checked was petrol. Had over half a tank so that was ok. Checked the little pump primer thingy on the fuel line. That was a bit soft so pumped it up. Still wouldn't start. Next I took the cover off checked the wires from the coil wires etc. They were on. After about 10 minutes of thinking what could be wrong I tried again. It started. So, not wanting to be stuck out there, we headed back. About half way back it stopped again. So we waited about 15 mins, then it started again.
Does anybody have an idea as to what the problem could be. I know a little about engines (cars and bikes mainly) so have come to the conclusion that its not fuel. I am minded to think that it is probably electrical.
Now I am told that the engine is a Johnson Seahorse 35hp 2 stroke. The year is somewhere around 1985. I haven't found the identity tag yet to confirm this. However, the casing has a decal on it that says Seahorse 25, so I am thinking that it may only be a 25hp.
Do these engines have kill switches on them. If so where are they?
Before I take the engine somewhere, would it be worth changing the coil packs?
Also, I noticed when the engine was running that when I turned the key to the OFF position the engine kept running. To stop the engine I had to pull the throttle right back and then it just stopped. Is this normal? On my friends boat you just turned the key off. I don't know if this is connected to my problem or not

Any help would be appreciated

 

[Fantasie 19]

Hello guys (and girls). I am in need of a little advice.
I bought my first boat last week, after a few years of borrowing my friends. It's only for fishing so I got a little 17ft Microplus.
The guy who sold it to me has stated that the engine has had a good service and was running fine.
So my first fishing trip! Everything started well. Boat launched easy, motor running and heading out to sea. After about an hour of running the engine just stopped. It was like I had hit the kill switch (I don't know if the engine has such a thing). So first thing I checked was petrol. Had over half a tank so that was ok. Checked the little pump primer thingy on the fuel line. That was a bit soft so pumped it up. Still wouldn't start. Next I took the cover off checked the wires from the coil wires etc. They were on. After about 10 minutes of thinking what could be wrong I tried again. It started. So, not wanting to be stuck out there, we headed back. About half way back it stopped again. So we waited about 15 mins, then it started again.
Does anybody have an idea as to what the problem could be. I know a little about engines (cars and bikes mainly) so have come to the conclusion that its not fuel. I am minded to think that it is probably electrical.
Now I am told that the engine is a Johnson Seahorse 35hp 2 stroke. The year is somewhere around 1985. I haven't found the identity tag yet to confirm this. However, the casing has a decal on it that says Seahorse 25, so I am thinking that it may only be a 25hp.
Do these engines have kill switches on them. If so where are they?
Before I take the engine somewhere, would it be worth changing the coil packs?
Also, I noticed when the engine was running that when I turned the key to the OFF position the engine kept running. To stop the engine I had to pull the throttle right back and then it just stopped. Is this normal? On my friends boat you just turned the key off. I don't know if this is connected to my problem or not

Any help would be appreciated

Going to assume you have new fuel... if you have next thing I'd start by changing the plug for new... if it still has a problem after that I've run out of ideas....

Post edit: the only reason I recommend plug change is that I had very similar issue start of last season, engine would run fine for a while and then stop.. I assume plug was knackered, and when it warmed up stopped... and besides, they only cost a few quid and it then rules it out of the investgation

 

[TQA]

The sudden stop is suggestive of an electrical issue.

It is easy enough to check for a spark. Remove plugs and place one with HT lead attached against the block. Operate the starter and check for a spark.

If no spark the kill switch is certainly high on the usual suspects list.

 

[okeedokee]

Thanks for the replies.
Fantasie 19, the fuel was freshly pumped that morning.
I am going to take the motor off the boat this evening and have it running at home, to see if it does it again.
TQA where is the kill switch? I have been trying to find a wiring diagram on the internet but haven't found anything yet. I don't think the keyswitch is wired correctly as I am sure the keyswitch should stop the engine when in the off position

 

[Ramage]

Did you remember to open the fuel tank vent?

 

[newWave]

The fuel line usually attaches to the tank and engine with a ball valve.
These valves may occasionally get stuck.
The pin that presses the ball to open up the line might be misalligned and due to boat movement it might lock the fule line.

Probably not the case, but still worth checking.

 

[okeedokee]

Sorry for the delay in my replies. They have to be approved by a mod first.

Thanks newWave. I have checked the fuel lines, and all seems OK. I am going to order a new fuel connector just in case.

I've got the engine off the boat now, and on a test rack with a water butt full of water. The electrics are all over the place. The red plug has been taken off and all the wiring is the wrong colours. Looks like someone has made their own loom for it.
The switch that stops the engine being started in gear has been by-passed so probably needs replacing. I haven't found anything that looks like a kill switch.
I've had to stop for tonight as lost light. I will be having another look tomorrow now

 

[BruceK]

On this era and make of engine it's common for the kill line to create a short at the switch or connectors.

 

[okeedokee]

Is there a cure for this?

 

[BruceK]

apart from doing a simple rewire and switch replacement? Not that I know of. However to give you a clue if this is the cause touch the body of the motor while starting or running. If you get a shock (like you would holding an HT lead) you have your answer for definite that the system is earthing. Though this isn't always the case if you have a faulty switch.
Also check the IU to coil leads for carbon deposits / arc damage on the connectors and that HT and LT leads do not touch the body of the engine. On my Evinrude / Johnson of that vintage the one of the leads would warm up with the engine, soften and collapse against the engine body and ground out reducing spark and so fouling the plug. Hence the ability to restart after a period once the plugs had dried out some. The problem got worse with carbon paths forming on the leads until only one cylinder was firing. (look for tiny black pin prick holes) New leads and wires all round solved that problem and the increase in power and performance was a joy. Goodluck

 

[okeedokee]

Thanks for the information BruceK.
I have had to re wire most of this engine now. I did find that the kill switch wires had been cut, and one was touching the casing.
I am going to order new coil packs, and have already ordered new plugs. Hopefully I will be able to try it out again next week. I will post how I get on.

Once again, thank you to all that replied

 

[jfm]

If it was a sudden stop and happened intermittintly as described it is likely electrical. Hard to be sure without hearing the thing of course. From the symptoms described I'd check/replace the starter key and check the ignition low voltage circuitry

This engine never had an oem kill switch. You could fit one if you wanted. The kill switch is simply a string operated switch which shorts the LV side of the magneto to earth when you want to stop the engine. you could wire directly to the magneto, or you could piggy back the wires that already run to the key-switch (obviously you have to pick the right pair of wires in the loom)