18 HP Johnson

[Gamecock]

I am brand new to the world of boating. I just bought a used (not sure of the year) 18 HP Johnson Seahorse. I tried to take it out on the water yesterday and couldnt get the darn thing started. On a couple of cranks it would act like it was about to come to life but would go out after about 3 seconds. The carb has been recently re-built but the motor hasnt been ran in a couple months. Every once in a while the motor would backfire when it was being cranked. I might have had the set up wrong when trying to crank. I had the hand control on START, I dont know what the "lean" and "rich" control does, so I had it in about the middle. But I'm not sure if I had the thing in the right gear. I'm assuming it has foward, neutral, and reverse and should be in neutral when starting. I had the gear shift in the middle (thing is not labeled) so im not sure if i was actually in neutral. If it sounds like the thing is set up correctly and just not starting, let me know. Or if it wouldnt start and i had it set up correctly let me know what it sounds like needs fixing. <br />Thanks for any help!

 

[Paul Moir]

Re: 18 HP Johnson

Your setup sounds right. The gearshift is in neutral in the middle. I don't think it would matter on your engine anyway. Did you choke the engine? I only mention it because you didn't. If not, you'll never get it started. Closing the choke closes a plate in the front of your carburator, giving the engine plenty of gas for cold starting. Once started you must open the choke fully on some engines, or partly on others until they warm up.<br />Also, did you pump the primer bulb on the gas line until it was firm? This fills the carburator with gas until the engine drivin fuel pump can take over.<br />If none of this solves your problems, post a question in the Johnson/Evinrude forum with your model number. The model number can be found on the nameplate on the transom bracket.<br />Good luck!<br /><br />EDIT: Looked like that just happened!!

 

[Gamecock]

Re: 18 HP Johnson

I did choke the engine, but I'm not entirely sure I was doing that correctly. I think I might have been doing it backwards (opening the choke when trying to start it). I'll give that a try. Thanks for the advice.

 

[Paul Moir]

Re: 18 HP Johnson

Look under the cowling to make sure the plate is closing over the front of the carb. Then you know you are choking the engine.<br />This makes for a high vaccum inside the venturi (narrow part) of the carb, where fuel is pulled into the air stream. Since the vaccum is high, it pulls a lot more gas into the air. Beyond the venturi is the throttle plate, which opens as you open the throttle.

 

[Gamecock]

Re: 18 HP Johnson

Thanks for the response. The motor was backfiring a lot when I was trying to start it, do you know what would cause that?

 

[Chinewalker]

Re: 18 HP Johnson

Have you had the spark plug wires off at all? It's possible the backfiring is caused by the plug wires being on the wrong plugs. There should be a small metal or plastic marker on one of the plug wires. It always refers to the top plug (on a 2-cylinder) and is usually marked as such. If the plug wires are reversed the motor can backfire as it's firing with the ports open and the cylinders full of unburned fuel instead of exhaust...<br />- Scott

 

[Gamecock]

Re: 18 HP Johnson

I've been reading through a lot of the posts here and I've read that the impeller should be changed each season. I've got a pretty good feeling that the impeller on this recently bought motor has not been changed in a while (definitely not this season). My question is this: could a faulty impeller be the cause of the engine not starting, or is the impeller something that only matters once the engine is running?

 

[BF]

Re: 18 HP Johnson

the impeller is a circular piece of rubber with vanes on it (like flat fingers) that fits around the driveshaft and is the water pump to cool the motor. Most motors have a "tell-tale" or "pee hole" so that you can see that water is being pumped when it is running. Some old motors don't have a tell tale, you have to look at the exhaust hole in the back of the leg (the one about 1/2 way between the prop and the motor) and look for water being spit out.<br /><br />The impeller will get hot and melt in only seconds if the motor is run out of the water. You need to have the LU (lower unit) in water or have "muffs" that attach to a garden hose and clip over the water intakes to start the motor off the lake.<br /><br />As for your starting... for cold starting my evinrude/johnsons:<br /><br />Attach fuel line.<br />Pump fuel bulb until it gets firm<br />Make sure engine is in neutral (shifter is straight up)<br />set throttle to start<br />pull choke all the way out<br />pull starter rope (usually 2-4 times)<br /><br />engine fires (briefly)<br />push choke all the way in immediately (I'm usually too slow and it stalls)<br /><br />pull cord again with choke in until it starts (1 or 2 pulls)<br />If engine starts to slow, give the choke a short blip (out then in as fast as you can). I may have to do that once or twice if engine's cold.<br /><br />Some engines need a more choke than what I describe, others (like mine) flood badly if you keep pulling with the choke out once it's fired the first time. You'll get to know what's right for your engine.<br /><br />By the way... setting the lean rich knob in the center is the right way to start. Use it to fine tune the idle mixture at trolling speeds.<br /><br />good luck.<br /><br />Brent

 

[Gamecock]

Re: 18 HP Johnson

I'm a little confused on what the lean/rich knob actually does, can anyone clear this up for me?

 

[Paul Moir]

Re: 18 HP Johnson

Sure. That controls the fuel to air ratio at idle. Engines need a richer mixture at idle than they do at full throttle. The numbers are around 1:12 at full throttle and 1:8 at idle. The proper idle mixture is dependent on a lot of small things with the engine, so they make it somewhat adjustable.<br />This is accomplished by the idle mixture needle valve. What it does on your carburator is to control the flow of gasoline under higher manifold vaccum conditions (which happen at and near idling) to a couple of extra ports, one of which is normally behind the throttle plate. It's through this valve and those ports that the extra gasoline is drawn into the engine.<br />The inital setting on your carburator is turned in (clockwise) until the valve lightly seats, then out (CCW) 1-1/2 turns. Then, while idling and warmed up, turn the valve in (CW) in 1/8 turn steps, giving the engine a few seconds to react. When it begins to sneeze (from running too lean), turn it out (CCW) until you reach the highest running RPMs.<br />Hope this explains it!