82' 115 hp speed and random rpms

[mherndon]

I saw another thread similar to this one, I just didn't wanna hijack his.

I have a 1982 115 HP Johnson. When I bought it (used), it would run for about 3 minutes, then slow WAY down. Noticed the priming bulb was deflated. I pumped it up and it did the same thing, repeatedly. I got home and poured the rest of the gas out. Couldn't take the fuel line out of the plastic gas so I filled it up with water, blew air thru the lines, drained, repeated about 4 times. Put new gas in it and hit the river. It ran GREAT for about 2 months.

Now, when I give it full throttle, it raises the bow up and acts like it is going to go but only goes about half speed. You can hear the rpm's fluctuating occasionally, from about half to wide open, then immediantly back to half. Finally, after about 4 minutes, the bow will FINALLY sit down, and 5 minutes after that, it will reach close to top speed and the rpm's remain fairly constant. I don't think that it gets quite there though. The bulb stays inflated but it feels like when I do squeeze it, it is kind of empty, like the fuel pump maybe.

When I stop, it repeats all of the symptoms over again.

Just cleaned fuel filter, installed 4 new Champion spark plugs, changed oil in lower foot, blew thru lines again. Any ideas?

 

[SparkieBoat]

Re: 82' 115 hp speed and random rpms

sounds fuel related, check fuel pump

 

[fsujack21]

Re: 82' 115 hp speed and random rpms

I had a very similar issue with my '81 115. Turned out to be a vaccum leak in the fuel lines. I replaced all fuel lines (including primer bulb) from tank to engine. I also replaced the internal lines from the fuel pump to the base of the carbs with 5/16" ethanol resistant line. If your engine has the quick conector at the base of the cowl, like mine did, I removed that and ran the line from the primer bulb straight to the fuel pump. Just be sure to route that line in a manner that turning the engine doesn't cause a kink in the line. This resolved all my issues.

Hope this helps

 

[emdsapmgr]

Re: 82' 115 hp speed and random rpms

The only time the fuel primer bulb will get hard is when you first prime it each day before starting. Once the engine runs, the bulb will get soft, but should not collapse. That's normal. When your engine starts to act up, what happens if you contantly prime the fuel hose bulb? An intermittent spark plug miss can also cause the problem you describe. Check for spark on each plugwire when underway with an inductive timing light. The flashes in the gun will show a misfire or weak firing.

 

[mherndon]

Re: 82' 115 hp speed and random rpms

The only time the fuel primer bulb will get hard is when you first prime it each day before starting. Once the engine runs, the bulb will get soft, but should not collapse. That's normal. When your engine starts to act up, what happens if you contantly prime the fuel hose bulb? An intermittent spark plug miss can also cause the problem you describe. Check for spark on each plugwire when underway with an inductive timing light. The flashes in the gun will show a misfire or weak firing.

When the engine starts to act up and I prime the bulb, it doesn't affect it. Sometimes, it sounds like it increases rpm and picks up a little bit, but then goes back down. I will check the sparks with the timing light soon. Thanks for the help!

Also, I tried to check the lines and they seem fine. I think that I am going to just replace them all. Wouldn't I be able to use a vaccum tester or something to check to make sure that the fuel pump is actually pulling correctly?

 

[emdsapmgr]

Re: 82' 115 hp speed and random rpms

If you prime the fuel hose bulb and it makes no difference, your fuel pump is probably ok. If you put a pressure gauge between the pump and the carb, then crank the engine, you should see about 1 psi.

 

[mherndon]

Re: 82' 115 hp speed and random rpms

If you prime the fuel hose bulb and it makes no difference, your fuel pump is probably ok. If you put a pressure gauge between the pump and the carb, then crank the engine, you should see about 1 psi.

My first thought was that the pump wasn't pulling enough fuel thru the lines. That make's sense though. I will try the pressure gauge and the timing light. Hopefully, I can find one of each to borrow! Should I also try to rebuild the carbs? A guy told me to put some "sea foam" in the gas and it would clean the engine. He said it's like $12 at AutoZone.

 

[SparkieBoat]

Re: 82' 115 hp speed and random rpms

sea foam is great but you have a fuel issue most likely, you should test your spark and compression first just to eliminate it, look at my sig below.

 

[Monte1961]

Re: 82' 115 hp speed and random rpms

Fog the carb/s with mixed fuel and see if it pics up or gets worse. That will help in determining if its fuel or electrical issue. You might want to add a inductive timing light and check all plug wires while your at it! Good luck

 

[emdsapmgr]

Re: 82' 115 hp speed and random rpms

If you have the remnants of dried fuel (gas gelatin) in the carb passages (or the jets) Seafoam may take a long time to dissolve it. You may find a gas cleaner, like a Gumout product may work faster.

 

[mherndon]

Re: 82' 115 hp speed and random rpms

If you have the remnants of dried fuel (gas gelatin) in the carb passages (or the jets) Seafoam may take a long time to dissolve it. You may find a gas cleaner, like a Gumout product may work faster.

I put some fuel stabilizer in it. I will try some fuel cleaner this time and try it. I think that I am going to do the timing light test this weekend. Thanks for all of the help!!

 

[mherndon]

Re: 82' 115 hp speed and random rpms

Alright. So, I cleaned both of the carborators with carb cleaner and put the fuel cleaner in it. I ran it a couple times and it seemed to run GREAT! One or two small hiccups but overall I was very pleased. Then, I added a whole can of Sea Foam to try to get rid of those couple of hiccups. I ran it a couple more times. The first time after the Sea Foam was a little more spotty then before. The second time, I was having a terrible time with it. Every time I would increase speed, it would shut off. even after idling for a while and then going at a slow speed for a while. I would finally get it up to top speed and after a couple minutes it would start hiccuping. After about 10 minutes, I would cut it off, swim then crank it back up and had to do all of that over again.

Well, I did a compression test and checked for spark on all four cylinders. All of them had good spark and the compression was: 120, 110, 112, 110.

What should I do next? It seems like it runs good when it wants to!! Oh yeah, and a trick i learned to get it going better is to put it into gear and accellerate then back it off realy quick. I slowly go further and further with the throttle until I am at full throttle and it doesn't cut off!

Thanks again!