59' Johnson runnin' rough

[Itec01]

Hi fellow boaters,<br /><br /> I bought a 1959 Johnson seahorse 18HP.<br /> It ran good for 20 min. and then started getting weaker and weaker. It now runs at about 40% of what it did.<br /> I checked coils, plugs gapped at .030, carb compression points gapped at .020. Just am running out of things to do. Any suggestions would be appreciated. I have run out of things to try.<br /><br /> I have a service manual on order, but the fish won't wait, haha.

 

[JR]

Re: 59' Johnson runnin' rough

You should use Champion J4C Plugs set at 0.030, points should be set at 0.020<br /><br />JR

 

[ShafferNY]

Re: 59' Johnson runnin' rough

Is there a little glass bowl on the bottom of the carburetor? If there is take it off and remove the stone filter, clean both of these up and try that, it's a common problem on my '56 5.5 Rudy. <br /><br />Does this have duel lines?? If so you may have a slight leak, check the tank to make sure it has pressure, try pressing the primer while drive it and see if that makes a difference? <br /><br />Let me know if any of this helps.

 

[Itec01]

Re: 59' Johnson runnin' rough

Hi ShafferNY,<br /><br /> I cleaned the filter in the bowl. And the tank is a pressurized one. I replaced the pickup in the tank and it has very good pressure. I triied pushing the button on the tank while the boat was full throttle and it made no difference.<br /> I don't know what to look at anymore.<br /> Thanks for the reply.

 

[rolmops]

Re: 59' Johnson runnin' rough

Hello.<br />There are three things I can think of<br />1 Sometimes the needle valves vibrate loose and start making a different, much richer, fuel air mix.This will happen gradually (20 minutes?).Try and see if reajusting helps.(close them a bit more)<br />2 On the rod that goes from the accelerator to the carburator, there is a clamp screw.This loosens up sometimes.without that clamp in the right spot you do not reach full speed. .Check to see if it is loose,and try to accelerate to full speed by pushing down on the rod where it gets to the carburator<br />3 The 2 screws that hold your cam in place are loose.When this happens your camfollower can no longer get into full speed position.Check again by accelerating by hand, right on the carburator.<br />This last one is much less likely to happen<br />Hope this helps.

 

[ShafferNY]

Re: 59' Johnson runnin' rough

How does it idle? or is it just top end that's lacking?<br /><br />You may have to take the carb apart and clean it, if the previous owner never ran it out of gas before storing it.<br /><br /> (When ever I'm done with my engine I unplug the fuel line and let it idle out of gas, because I never know the next time I'll get to use it, one day or two months. Just good insurance.)

 

[Itec01]

Re: 59' Johnson runnin' rough

Hi ShafferNY <br /><br />Thanks for the reply, It idles fine when I get on the throttle it goes 40% of what it should go. It backfires once in a while through the air intake. I cleaned the carb more than once. Replaced the seat and needle and the float.<br /> It does miss now and then also when I throttle up.<br /> The bottom cyl. seems to be running cooler then the top one. I'm wondering if I don't have a leaky head gasket. Water may be getting in with the fuel on that cylinder and causes it not to burn properly.<br /> Thanks again

 

[ShafferNY]

Re: 59' Johnson runnin' rough

Usually one plug will be exceptionally cleaner than the other if it's a leaky head gasket. The cleaner plug is the one that is leaking.

 

[Itec01]

Re: 59' Johnson runnin' rough

Thanks to all that helped on this.<br /> I did buy a head gasket, I would like to look at the pistons to see what shape they are in and I bought 2 new condensers to replace the existing ones.<br /> I did buy a new coil yesterday and need to swap it around to make sure the one I left in isn't bad.<br /> I am also batting around the idea of replacing the spark plug wires.<br /><br /> Continueing the saga....<br /> I will get this.<br /> Oh one more thing, could this possibly be a valve problem but the problems I've outlined. Thanks again

 

[Bear]

Re: 59' Johnson runnin' rough

Check this out too:<br /> http://www.maxrules.com/fixfaq.html#coils <br /><br />Good luck!<br /><br />/Bear

 

[Itec01]

Re: 59' Johnson runnin' rough

Thanks Bear <br /><br />I'll see if that helps.

 

[ShafferNY]

Re: 59' Johnson runnin' rough

If your going to chage a coil, or both, you might as well change the plug wires, it's not hard at all, and it's good insurance out on the lake.