1979 johnson runs sluggish

[dirtdriver11]

I got a 1979 Johnson Javelin 100hp (100TLR79S). Its on a 1979 Charger 16ft. tri hull. The motor sounds good, but the top speed is about 25 mph. Sometimes it sounds like the motor is running smooth around 20 mph and then all of the sudden it takes off to 25 mph. Every once in awhile it sounds like it goes into nuetral, it slows down but the motor is still revving up. If I throttle down and then back up it comes right out of it and takes off. I guess my question is shouldn't this motor have a faster top speed? I have replaced the spark plugs with the proper champion plugs, one new coil, changed the lower end oil, and disassembled and cleaned the carbs. The tach does not work so checking the rpms is not an option. Could the throttle control cables be out of adjustmen, if so, how do I adjust them and where should I adjust them to? One more thing, there are two holes side by side on the back of the motor right below the engine itself, is it supposed to be shooting water out of them, they are maybe 1/2 inch in diameter.

Thanks

 

[crb478]

Re: 1979 johnson runs sluggish

It sounds like you have more than one issue going on. First I would check the compression and verify the spark on all four cylinders. Hopefully compression is over 100psi and spark will jump a 7/16 gap with a strong blue spark. Then I would check your prop to see if it has a spun hub. Mark a straight line across it and see if it still lines up after the boat seems to go into neutral with the motor still reving. Lastly how did you clean the carbs? Did you take them all the way apart and let them soak? Did you pull out all of the jets and run a wire through them and then blow every thing out before putting it all back together with new kits? And when was the impeller last changed? It can ruin you day and your motor real fast.

 

[dirtdriver11]

Re: 1979 johnson runs sluggish

It sounds like you have more than one issue going on. First I would check the compression and verify the spark on all four cylinders. Hopefully compression is over 100psi and spark will jump a 7/16 gap with a strong blue spark. Then I would check your prop to see if it has a spun hub. Mark a straight line across it and see if it still lines up after the boat seems to go into neutral with the motor still reving. Lastly how did you clean the carbs? Did you take them all the way apart and let them soak? Did you pull out all of the jets and run a wire through them and then blow every thing out before putting it all back together with new kits? And when was the impeller last changed? It can ruin you day and your motor real fast.

I took the carbs apart except for the jets but I did not soak them. I don't when the impellar was changed. I just bought the boat and was told it hasn't been ran in 2 years, could the old gas be causing any of this?

 

[dirtdriver11]

Re: 1979 johnson runs sluggish

Compression is over 100 psi and it seems to have good spark at 1/2" or more. The butterflies in the carburetor aren't even opening half way, could I be missing part of the carb linkage? There is a connecting rod for the choke and one to the throttle. Does anybody of a picture of a similar motor I could look at?

 

[tashasdaddy]

Re: 1979 johnson runs sluggish

http://forums.iboats.com/showthread.php?t=299680

you waste your time on the carbs, they have to be done properly. may have a spun prop. 1979 has a tale tell (Pee) outlet on the lower cowl starboard rear, water should come out there, hose may be clogged up.

impeller definitely needs to be changed.

 

[emdsapmgr]

Re: 1979 johnson runs sluggish

If the engine runs erratically, you may be dropping a cylinder. You need to know if you are getting solid spark to all 4 cylinders when you are running under load. An inductive timing light will help you with this. That engine will normally spew a lot of water out the two exhaust relief holes at the top of the midsection when on plane. The new factory compression on that engine would have been in the 125 to 130 range. The fact that the carbs don't open all the way is probably an adjustment issue. Make sure you sync and link the engine according to the factory manual and then readjust the throttle cable back by the engine to insure that you get the carb butterflies to open all the way. I would not run any outboard on 2 year old gas and expect it to run right. You could have some water in the tank.

 

[dirtdriver11]

Re: 1979 johnson runs sluggish

what exactly do you mean by link and sync? i also checked my lower end oil the next trip after I changed it and it is kind of milky grey with a metallic look, is that normal?

 

[emdsapmgr]

Re: 1979 johnson runs sluggish

The lower unit oil should be a clear oil, usually with a tint of color, like either amber or light green. The oil gets a milky appearance when water leaks into the gearbox and mixes with the oil. Double check the two seals on the gearcase plugs. If they look ok, you should have a pro do a vacuum/pressure check of the lower uni to see if it needs to be resealed. Gearcases don't like water inside, so you should resolve this before you continue running it.

 

[dirtdriver11]

Re: 1979 johnson runs sluggish

Now, the fitting for the fuel on the bottom of the carb is leaking, how can i seal that since it is just pressed in? How do i adjust the linkage for the butterflies in the carb and what exactly does link and sync mean?

 

[emdsapmgr]

Re: 1979 johnson runs sluggish

The factory manual describes how to set the sync and link-the relationship between the throttle advance and the spark advance. There are pictures that show how it is to be done. Esp important if carbs have been off the engine. Is the leak in the bowl fitting or the hose connection itself? The original hoses under the cowling are not capable of handling today's ethanol fuels and over time will deteriorate and leak. Recommend that you replace any original hoses with the 2009 versions. If the bowl fitting is leaking, you should be able to get a replacement bowl. If no longer available as new, you should be able to locate a used replacement. You may have to transfer the jets from your current bowl to the new one.