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My 1996 48 Johnson SPL cuts in and out after around 3000 rpm. A shop put in and synced the carbs and installed a new fuel/water separator. I have replaced the fuel pump, gas tanks, fuel lines, hose clamps, tried the primer bulb when the problem occurs and don't know what else it could be. I was told by the shop it was a fuel problem for sure but obviously they didn't fix it so does anyone else have any advice? At my wits end and could use the help. Thanks!!!!
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Your motor '96, could possibly have the shift sensor, it seems the earlier 90's they started doing that. But, still not positive on your motor? Look for an electrical switch at shift linkage on motor.
Good luck.post back if find anything. -
Thank you, I will definitely post back once I resolve it because it seems common to a lot of people. As stated I pretty much eliminated a fuel problem and it runs ok at low rpm so it's time to look electrical. Waiting on a manual for it as well.Comment
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Possible success
Threw a Hail Mary and put new plugs in today because the other plugs were a year old. The plugs were changed by either my dads friend or a shop last year and were gapped incorrectly. I put correctly gapped plugs in and took it to the lake. Took her up to 4000 rpm after some warm up time and only skipped once. Drove it back and forth for about a half hour through different rpm ranges and no skipping. I hope it's fixed and this wasn't one of those the motor runs good today but smacks me in the face when I go to the sound. Could the incorrect gap on plugs really cause that or should I expect the smack?
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Hopefully it is fixed. Improper gaps cause misfires. Even some new plugs you buy can be bad, it has happened many times. Does motor go to 5k RPMs? Are you just holding at 4k? Being conservative?
Good luck, always go out with other boats, or a kicker for backup. If the sound is a distance? Also a good radio. I recently called coast guard because I had one motor die, and they passed a message to my family that I would be 3 hours getting back to dock, as my other motor by itself could only go 12 mph on my boat 30-35 miles out. They were happy to pass message on, and stood by to hear we made it in safely. I did thank them for their assistance.Comment
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Manual In
Got the manual in today and didn't find a shift sensor but really good info on a "SLOW" override from the power pack if the engine temp sensor is either bad or getting interference from the spark plug wires by being too close. It could also be caused by a sticky thermostat causing an actual high temp in the motor causing it to "run between 2000-3000 rpm". I'm going to get a new thermostat because I dought it was ever changed prior to me owning it and secure the sensor wires away from the plugs. I also was leaving my motor in the up position (like if I was hauling the boat) for weeks between fishing. Maybe that would mess with everything or lodge something in the thermostat and cause my issue??? Don't know but it ran well last time and I feel way better to narrow some stuff down. Manual is already worth it's weight in ****! Thanks and will post back if I have the ah ha moment.Comment
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Well after a good trial one week later I'm back to the same issue. On Friday took it out and it was missing at low speed around 2000 rpm, after 10 minutes it ran well all day. at the end of the day at 3000 rpm it missed over and over bucking up and down. Ran it back to port at 2500 rpm with no problem. The entire fuel system from the tanks to the pump and carbs is new and triple checked. Anyone have any advice? What in the ignition side would be this kind of intermittent problem? To add the engine does miss at idle and it runs rich at idle and shakes a lot. Would a coil pack or voltage regulator do this? I've tested the temp sensor that was good but didn't get any continuity through the blocking diode on either polarity. Could that be it? Thanks for anything I can get at this point!Comment
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Not a 96, it's a 95!
Such a dope. My motor is a 95 not a 96. At any rate I've been searching forums high and low and found someone with the same exact motor same exact problem. That person like I did replaced all fuel related parts and no luck. Then that person pulled the thermostat and found it plugged solid replaced and problem was resolved. I took mine out today and it was dirty and it was so stuck I broke it taking out and it looked like junk. I will replace and follow up with progress. I also got a new dual coil assembly just because I like to throw $ away ha ha. I wasn't able to find a timing coil in the parts list or the book so I'm not sure about that part solarman. Thank you and I will repost as said.Comment
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Finally got it! Pulled the thermostat (no good) and changed the coil pack and had the first problem free day of the year! Fished from noon to about ten o'clock at night not a single hiccup. A huge plus is I only burned 6 gallons of gas as oppose to the 12 I used to go through with the same amount of driving!Comment
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I thought I fixed it but here I am a year later dealing with it again... It's so intermittent I cannot pinpoint the cause. After replacing the thermostat last year no issues all season, pulled it out this year doing the same thing every other time I run it. I will not rest until I have this figured out! Once again any suggestions are welcome. Someone out there has to have the same issue and resolved it.Comment
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Found it
Found the heart of the issue, bare wire behind the power pack. I was checking wires behind my ignition switch while the motor was running and actually cutting in and out and got a wall outlet type shock. That must have lit my light bulb because it got me thinking about ignition... I read up on it in my manual and with some advice I took the wire that was suspect in shocking (black/yellow shut off to power pack) off. Running the engine at 3000 rpm cutting out the wire was getting 200-250 volts cutting back in no voltage. It's not suppose to have voltage running through unless you turn the key to shut the motor off. That's when I found a cut in the wire by the switch and found an even bigger one after removing the power pack. I will not dare to say I've finally got this licked as I have thought that before but damn this feels good! Hope this helps someone else having troubles.Comment
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