1996 115hp stumbles at 30rpms

[bradley3054]

Im new to this site but need help so i signed up lol, Im also new to this engine never experienced a picky enginge like this before lol. Well heres my problem, i bought the boat and the guy told me to not put high octane in the boat but i forgot because im use to gas engines liking high octane and being it hasnt been out since the year before it would do it some good. well i stuck it 100$ worth of high octane in it and starts up fine easy and idles great but when rpms get up to 30 it stumbles real bad. i asked the guy who originally owned the boat about it and he said high octane will make it run like crap and stumble real bad. 4 weeks later got some free time to go back on the water but day before i drained 15gal out of in to containers and put fresh low octane gas with 50:1 mix and it ran beautiful all day and fast! got home sat for a week exatly and we went back out and it started the same crap over again but not as bad sometimes it would run great or it would stumble at high rpm. The following day we went back out and i added 15 gal of low octane to see if that will help but nope no difference. WHats the deal here is it true these engines hate high octane? btw i did change the fuel water sep after my first use, but i havnt been on my best a game with the treatment stuff but i cant see it would make that much of difference or am i worng and the fuel water sep is filled again because of the ethanol? help anyone im trying to have fun with tube lol low speeds kinda get old

 

[pvanv]

Re: 1996 115hp stumbles at 30rpms

The seller was full of BS. Higher-than-needed octane will not ever hurt a thing. Period. Odds are you need to inspect the entire fuel system and thoroughly clean everything involved. Also could be leaking air into the suction side of the fuel system. But it could be a lot of things, not just the fuel system. Either see your dealer, or get a factory service manual and start inspecting the fuel system, as it is the most likely surce of the issue.

 

[bradley3054]

Re: 1996 115hp stumbles at 30rpms

The seller was full of BS. Higher-than-needed octane will not ever hurt a thing. Period. Odds are you need to inspect the entire fuel system and thoroughly clean everything involved. Also could be leaking air into the suction side of the fuel system. But it could be a lot of things, not just the fuel system. Either see your dealer, or get a factory service manual and start inspecting the fuel system, as it is the most likely surce of the issue.

from my experiance with other engines when its a fuel issue the motor will act like its dying or loosing power, but mine is acting like a two stroke engine hitting the rev limiter. and this doesnt explain for the one day she ran for 8 hours amazing. The motor will shake real bad that kind of stumble. btw finding a dealer around me for this engine could be a issue prolly gotta research that too

 

[bradley3054]

Re: 1996 115hp stumbles at 30rpms

what will running lean sound like? also what is the correct mixture for 50:1 mix i was told 2 ounces for every gallon that correct?

 

[pvanv]

Re: 1996 115hp stumbles at 30rpms

what will running lean sound like? also what is the correct mixture for 50:1 mix i was told 2 ounces for every gallon that correct?

Too lean can lead to popping through the carb. 50:1 is approximately a pint in 6 gallons. (50 oz. of fuel for 1 of oil).

 

[TOHATSU GURU]

Re: 1996 115hp stumbles at 30rpms

Popping and one pint of oil for every 6 gallons of gas. Did someone remove the oil injection off of the engine? That would be a sign of the engine having being worked on by someone who was mechanically stupid. You need to get a service manual and start troubleshooting the engine. There is no shortcut to troubleshooting.

 

[bradley3054]

Re: 1996 115hp stumbles at 30rpms

Ok well its not popping and i have a tech book. Yes the oil injection tank was taken off

 

[TOHATSU GURU]

Re: 1996 115hp stumbles at 30rpms

Then it's not running lean. Start with the manual and pick one of the engine's three main systems and start the diagnostic troubleshooting. Chances are that the problem is fuel system related, but with the oil injection system removed, there is no telling what else has been screwed up too. The engine will run without the oil injection system, but will tend to foul out spark plugs and not run as smooth.

 

[bradley3054]

Re: 1996 115hp stumbles at 30rpms

Someone told me it could be my coil pack, how do you properly test the coil pack to see if its putting out enough through all rpm ranges?

 

[pvanv]

Re: 1996 115hp stumbles at 30rpms

"Someone" doesn't have a clue, and is guessing. There isn't any such thing as a "coil pack" on that motor. There is a CD, and there are four ignition coils, the whole system driven by four pulser coils. The test procedure in the Factory Service manual calls for analog ohm meter testing. You can also test the input to the ignition coils (from the CD) with a DVA meter.

Don't guess, Diagnose, with the Factory service manual as your guide.

So... Start by getting a Factory service manual (from any dealer, including me). Don't bother with any of the aftermarket manuals. Also pick up a good Analog multimeter (not a digital unit), that has a resistance testing voltage of 3vdc or less, and preferably has DVA capability. Then learn how to take readings, and start at the beginning, checking the fuel, electrical, and mechanical systems.

 

[bradley3054]

Re: 1996 115hp stumbles at 30rpms

"Someone" doesn't have a clue, and is guessing. There isn't any such thing as a "coil pack" on that motor. There is a CD, and there are four ignition coils, the whole system driven by four pulser coils. The test procedure in the Factory Service manual calls for analog ohm meter testing. You can also test the input to the ignition coils (from the CD) with a DVA meter.

Don't guess, Diagnose, with the Factory service manual as your guide.

So... Start by getting a Factory service manual (from any dealer, including me). Don't bother with any of the aftermarket manuals. Also pick up a good Analog multimeter (not a digital unit), that has a resistance testing voltage of 3vdc or less, and preferably has DVA capability. Then learn how to take readings, and start at the beginning, checking the fuel, electrical, and mechanical systems.

Whats wrong with the sealoc manuals? i have one of those that came with the boat?

 

[pvanv]

Re: 1996 115hp stumbles at 30rpms

The Seloc manuals tend to cover "all models, from 1966 through 2001", or something like that. They tend to be too general, and don't always get to the specifics for a particular model. They're the "readers digest condensed version". Yes, you might be able to use an advertising brochure to repair a motor as well, but it wouldn't address the nitty gritty details. The devil is in the details, you know. The Factory manuals are written by the Factory service guys. I use Chevy manuals to work on a Chevy, and I use Toyota parts to repair a Toyota. Same holds true for outboards. Yes, since they are now obsolete, Tohatsu has grouped the 2-stroke manuals together in a single publication for the 1- and 2-cylinder motors (and another for the 3- and 4-cylinder motors), but the actual original information is there, in all its content.

 

[bradley3054]

Re: 1996 115hp stumbles at 30rpms

I manage to diganose and get it pin pointed down to ether my gas in the tank or the carbs, its def a running issue, not prop. I changed fuel water sep so its not it and filter is clean as possible and so is sediment bowl. My pulgs could be reading a little rich there is always oil on them after i kept pulling them. Gonna try using my aux 6 gal tank i have from another boat with fresh gas to see what happens to eliminate my fuel problem then itll be down to my carbs if its not gas. Just weird how she ran good with full tank of fresh gas one day then sits for a week and runs like crap again

 

[pvanv]

Re: 1996 115hp stumbles at 30rpms

Your problem could still be almost anything. Definitely a good idea to try the portable tank and a new primer hose. A leaky o-ring in a fuel connector can cause problems at higher speeds. And, since the motor was hacked up (and the oil system removed), you will need to run 50:1 mix, which will indeed be too much oil at idle, so the plugs will probably be a little oily when you shut down. Running premix will force you to change plugs more often.

 

[bradley3054]

Re: 1996 115hp stumbles at 30rpms

ive been thinking, since my boat ran so good one entire day after fresh full tank of gas, its obvously not tuning! so ether something in my bowls and something along with the fuel lines or gas tank or fuel flow. I wonder when i put fresh gas in it stirred up my gas tank and after it sat for a week something and alot crap or water settled for that week and maybe also why its doing it. but wont know for sure till i hook up the aux tank. btw i also have two fuel lines one for the main motor and second for the small 9.9 motor that use to be on my boat before i baught it.

 

[pvanv]

Re: 1996 115hp stumbles at 30rpms

You are headed in the right direction. Diagnose the issue. Could still be other things besides the fuel system. Try the portable tank, get the carbs properly cleaned, test the ignition system, and finally the mechanical system. As you go along, you will uncover the problem.

 

[bradley3054]

Re: 1996 115hp stumbles at 30rpms

Well kinda stumped now, hooked up the aux tank with fresh properly mixed gas and still the same, pulled the carbs apart and cleaned them still noth, idk

 

[pvanv]

Re: 1996 115hp stumbles at 30rpms

What method did you use to clean the carbs? Are the float heights correct? Did you use a known-good fuel hose and primer? Did you verify the link and sync? Have you tested the ignition components? What is the compression? How good is the fuel pressure? How about the fuel pump vacuum (on the suction side)? Is the old oil-mixing t-fitting still in place, or was the hose replaced? Still a lot to go through.

 

[bradley3054]

Re: 1996 115hp stumbles at 30rpms

What method did you use to clean the carbs? Are the float heights correct? Did you use a known-good fuel hose and primer? Did you verify the link and sync? Have you tested the ignition components? What is the compression? How good is the fuel pressure? How about the fuel pump vacuum (on the suction side)? Is the old oil-mixing t-fitting still in place, or was the hose replaced? Still a lot to go through.

I took the carbs off one at a time and took them apart and sprayed every port out and took float off and made sure every thing was clean, i did not see a way to adjust the carb float but the float looked fine no holes or bends. I honestly believe with the mixing system all they did was take off the oil tank and bent the sensor thats all i see, the hoses are still laying there. How do you properly test fuel pressure? im thinking that might have something to do with it. Because i was on the boat yesterday and started off with the morning same thing no fast then 3000rpms then i got a idea have some play with the throttle as i pump the primer and we actually got the motor to almost run that stumbling out of it. since i had a second fuel line on there i took the primer off of it and switch the main lines primer with the secondary one cuz its newer and stiffer, that didnt make a difference. I need to take off the second line because i dont have a second engine on the boat it was taken off it kicker bracket and when i played with its primer i notice the line leaks so erase that to get rid of possible air pockets and next thing is fuel pump i feel like it doesnt have enough pressure. I dont know the compression yet but i did test it by having the engine running and unplugging each spark plug wire and it was running on one clyinder pretty decent actually. The fuel pump works by vibration to work the diaphram right? Have to look at my book to see were exactly it is.

 

[pvanv]

Re: 1996 115hp stumbles at 30rpms

1. You did not thoroughly clean the carbs. In order to do that... They must be completely disassembled (including the jets and emulsion tube nozzles), submerged in real carb dip for 4 hours at room temperature, and then liberally blown out with generic carb spray. For all 4 carbs, expect to go through at least 2 cans of spray. When reassembling, confirm float height.

2. Fuel pressure is measured with a pressure/vacuum gauge. Likewise, you can use the same gauge on the suction side of the pump.

3. If the oil mixer is still connected, with no oil tank, it could supply air instead of oil, and that could be your problem.

4. The fuel pump is operated by alternating pressure/vacuum from the crankcase, moving the diaphragm. If the diaphragm or check valves are dirty, damaged, or worn, you could have fuel delivery problems.

5. Also verify link and sync.