Help my Javelin

[Rick paredes]

I have a 76 85hp Johnson Javelin. I have installed card kits and new spark plugs and it is sputtering. It also only gets my 18' pontoon up to 15 mph without a load. My 55hp yamaha did that. so, I was expecting a little more speed with this engine. Any ideas of where I need to go from here to get this running a little better?

 

[HybridMX6]

Re: Help my Javelin

Have you done a basic health check of the motor? Compression, good strong spark, and sure the fuel is getting into the cylinders properly?
If it's sputtering, sounds like the idle may need adjusting, but if it's that slow on the water, something else other than idle is not functioning correctly. I would think even a 55hp Yamaha should push a pontoon more than 15mph, so I'm wondering about your setup.

 

[Rick paredes]

Re: Help my Javelin

Compression is good 120 on all 4 cylinders. I have not done a spark test yet. Is thier a special tool that needs to be used to check this?
Thanks for the reply

 

[HybridMX6]

Re: Help my Javelin

You should be able to get an adjustable spark gap tester at any local auto parts store for around $10. The spark should be a strong blue spark and should just a 7/16" gap. It will have instruction on it for how to hook it up. You will probably need help doing it unless you have a remote ignition switch so you can stand by the engine and turn it over while also watching for spark. I just have my wife do it, all she has to do is turn the key.
Did you set the idle properly? I'm not too familiar with your specific engine, but I had a '78 35hp which had a knob on the front of the carb cover for rich or lean. Settings need to be done when the engine is warmed up, and idling on the water, not on muffs or in a bucket.
The compression sounds fine, so that just leaves fuel and spark. Did you take everything on the carbs off/apart, clean each passage, blow out, etc? Even the little plugs? It doesn't take much to make it run poorly.

 

[Rick paredes]

Re: Help my Javelin

I basically just changed the floats,seats and needles and sprayed the cards down with carb cleaner. My carbs do not have air fuel mixture screws. It does have two screws on both sides of the carbs that have another screw behind it. Is the the passage you are talking about blowing out? The screws looked like they went in under the two silver caps that were in the float bowl and the guy at the marine shop said he never has changed those when doing a carb rebuild. I will pick up a spark tester and try that out and see what happens.

 

[HybridMX6]

Re: Help my Javelin

Since I'm not that familiar with your engine, I'm hoping someone with more knowledge will get in on this. From what you describe, that sounds like the high speed jets in the carb. You don't need to change them, but you need to get them out and clean them thoroughly. There is a special tool required to get them out, I believe Tashasdaddy has a diagram of it somewhere. You can make one yourself, or buy one. The freeze plugs just pop out with a whack and a center punch, and new ones pop in with a whack and a socket on an extension. You need to pull the carbs apart completely, clean every thing you see, and blow compressed air through every passage you can find, even whatever is behind the silver plugs before you put new ones in.

 

[crb478]

Re: Help my Javelin

Check your spark first since it will cause it to run poorly it it is intermittent or not sparking on all cylinders. I have to disagree with the marine shop advice that you got. To Clean the carbs they should be totally taken apart and have the jets pulled out and then soaked in a container of carb cleaner. You should also pull the silver disk and make sure that the holes are clear and clean. That is why they give you new disk in the rebuild kits.

 

[Rick paredes]

Re: Help my Javelin

Thank you gentlemen, I will try that this weekend and see what happens.

 

[HybridMX6]

Re: Help my Javelin

Good luck. Post back with your results, good or bad, and we can go from there if it's still not right.

 

[Rick paredes]

Re: Help my Javelin

Good morning,
I re-rebuilt the carbs and did a spark test and found out that the two coils on the left side were not firing. I replaced those and it ran great but, still only getting 15 miles an hour top speed. My boat is a 18' 1994 Playbouy pontoon. Is this correct for what I have?

 

[Chinewalker]

Re: Help my Javelin

Have you done anything to the propeller? If the 85hp came from a small runabout and you haven't changed the prop, then it is probably the wrong prop for the application. Your motor needs to be peaking in the 5500 RPM range. If you've got a prop with too much pitch on there, it's akin to trying to drive uphill in 5th gear while towing a trailer - ain't gonna happen. If all else is good, assess your prop... A good marina ought to be able to set you up with a better propeller for a 'toon... something with lower pitch and likely more blades.