1970's Johnson 40horse SeaHorse

[Peace]

Hi. I have a 1970's? Johnson 40 horse SeaHorse motor that cuts out after 10 mins of warming up the motor. I believe the problem lies with the coil. Being pretty new to the outboard repair scene, could anyone please provide me with a link to an online manual for replacing the coil? Would appreciate a site with pics/diagrams to help me out. Also, how am I able to find out the exact date this Johnny was made? Thanks for the assistance, Peace.

 

[Peace]

Re: 1970's Johnson 40horse SeaHorse

Also, could I replace the coil with one from any other 1970's Johnson or Evinrude 40 horse?

 

[Paul Moir]

Re: 1970's Johnson 40horse SeaHorse

Welcome to Iboats, Peace!<br />We're going to need a model number, since during the 70's there were a few different ignition systems. Look on the top & side of the transom clamps/steering swivel bracket for a nameplate with the numbers.<br /><br />In the mean time, has the cooling system been maintained recently? (waterpump, thermostat?)<br /><br />Unfortunately, there's no online manuals for these outboards. Seems some people are still making a tidy profit off them. There's lots of places to buy one online, but if you don't want to purchase one, check your local library. Once we've got your model number we can point you toward a few manuals if you like.

 

[Peace]

Re: 1970's Johnson 40horse SeaHorse

Hi Paul. Thanks for the friendly welcome. Not too hard to tell I'm new to this huh?<br /><br />The numbers I have found are:<br /><br />Model # = 4OR73D<br />Serial # = 107366<br /><br />Cheers, Marty.

 

[fireman57]

Re: 1970's Johnson 40horse SeaHorse

Check your spark first. After the 10 minutes of warm up when it dies do a spark test. If you have an orange or yellow spark that is an indication of a weak spark. Should be bright blue and if you get bit by it it should blow the snot out of your nose. If you have a weak spark swap the coils and see if it follows. Then you can change the powerpack. Even after all of this the best advise I can give you is get a manual.

 

[OBJ]

Re: 1970's Johnson 40horse SeaHorse

Hi Marty....your engine is a 1973 40hp. The ignition is a standard point/condenser system. A local library would probably stock a generic manual like Seloc or Clymers.<br /><br />I would ask as Paul did, you should be sure the engine is not overheating causing it to stall. Don't take long if the cooling system is not up to par. A quick way to find out, start the engine. After a few minutes, put your fingers on the flat area on top of the block just in front of the head. You should be able to leave your fingers there for several seconds without having to pull them away. If you can't and the area is extremely hot, better check the impeller and t-stat.....and don't run the engine until you do.<br /><br />Just a couple more questions....do you know anythig about the engines maint history? And when it runs, does it miss or cough? Is it hard to start....in the water?

 

[Peace]

Re: 1970's Johnson 40horse SeaHorse

Nah mate, no idea about the maintenance history. Getting plenty of spark. Engine is getting hot, and is heder to start in the water then out. Whats the t-stat? cheers, Marty

 

[Paul Moir]

Re: 1970's Johnson 40horse SeaHorse

T-stat is the thermostat. It should be in the head (where the spark plugs are) underneath a plate held on by 3 bolts. You can remove the plate and remove the thermostat for inspection/testing. And while it's off, you can run the outboard in water (with the plate temporarily on) and observe water flow out through the large hole on the back of the engine's midsection. <br /><br />You say you have started this engine out of the water? I know that the form of 'muffs' it needs are unique and a little hard to get. So how did you cool it? If you ran it without any water, then you likely roasted the water pump's impeller. No big deal, you needed a new one anyway.

 

[Peace]

Re: 1970's Johnson 40horse SeaHorse

Yep. I was mucking around with the choke switch so tested it out of the water. As soon as it fired I hit the stop button so it hasnt run out of the water for any longer then 2 or 3 seconds, just long enough to start her up. Dunno about the previous owner though. Also I think I need to replace the bearing in the big wheel on top of the engine, as its starting to get a bit wobbly. I can think mechanically but have never worked on a 2 stroke before, be that a lawnmower, motorbike or outboard. In your opinion do you think I could be able to replace the bearing, impeller and coil myself, if I got a manual, or would you suggest these repairs be undertaken by a qualified mechanic. Also are these repairs likely to be costly, as the engine is probably only worth a couple of hundred New Zealand dollars. <br /><br />Thanks again, Marty

 

[fireman57]

Re: 1970's Johnson 40horse SeaHorse

The impeller and coil should be easy but definitely get an OEM manual for the bearing. The manual will easily pay for itself time and time again.