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Full throttle fail

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BuckB

New member
I have a 1989 Bass Tracker with a 89 Johnson/Tracker V4 90HP.
It starts great and once warmed up idles good. When I take off I seem to get good power for the first 1/4 of throttle. When I push it to full throttle it falls on its face. Sometimes I can run it a few minutes and it will suddenly fire off and run great but most of the time it doesn’t. It normally pushes my boat at about 34mph loaded but when it fails it will run 8-26mph. I have ordered carb kits and will rebuild later this week. Is there anything else I need to look at. Thanks for your help.
 
Many people pick the carburetors first for some reason.-----Not much can go wrong with them.-------Do yourself a favor and do a compression test. ----Post your values here.-----Then check for spark on each lead.----Good spark can jump a gap of 7/16" on a test device with an open gap.------Or test run with another fuel tank and hose.----Or test run with a timing light hooked up 1 cylinder at a time and see how spark behaves.-----If it SUDDENLY fires off I would be looking for ignition issues.-----And it could be as simple as a bad plug wire / boot arcing to latches on the cowling.
 
racerone said:
Many people pick the carburetors first for some reason.-----Not much can go wrong with them.-------Do yourself a favor and do a compression test. ----Post your values here.-----Then check for spark on each lead.----Good spark can jump a gap of 7/16" on a test device with an open gap.------Or test run with another fuel tank and hose.----Or test run with a timing light hooked up 1 cylinder at a time and see how spark behaves.-----If it SUDDENLY fires off I would be looking for ignition issues.-----And it could be as simple as a bad plug wire / boot arcing to latches on the cowling.
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Thanks for the swift reply. If the weather cooperates I will try to get the boat out tomorrow and check the compression, spark and timing then post my results. I have replaced the fuel line from tank to motor as it was corroded and feeling mushy and I was afraid it might be collapsing internally and constricting the gas flow.
 
Hmmm! You use ethanol fuel? Then I just MIGHT pick on the carburators first. When did the aforementioned symptoms begin?
 
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timguy said:
Hmmm! You use ethanol fuel? Then I just MIGHT pick on the carburators first. When did the aforementioned symptoms begin?
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I’ve been using 87octane straight from pump but am considering going to premium. It’s just so stinking high this year. The problem started last season at the end of summer. It would do it just about every time I went out but only for a short time then it would run fine. This year I’ve only been out twice and both times had to cut trip short because it ran bad more than good.
 
Quick note to let everyone know I haven't disappeared. I haven't done anything more with the boat due to the weather. I live in Kentucky, and we had tornado weather pass through yesterday. But today is a new day and looking nice out there. As soon as my son can go with me will get the boat out and run some test. To be clear I am not a marine mechanic but I worked construction most of my career and then into facility maint. the last 15 years. Last job was a Chief Engineer at a hotel and resort in Alaska. With that said, I am not new to troubleshooting and mechanics, however I'm not the best mechanic either. So please bear with as I work through this boat issue. I appreciate everybody's input and hope to get up and running soon. I am now semi-retired and can't really afford to take the boat to a shop. Thanks again and i hopefully will be posting some results this evening.
 
Excellent. Alaska has got to be on my wish list, certainly a place to get away from things. I have a couple remote camps in NW Ontario sure can't get enough of that either.
Question: Is the VRO still operating? They are typically destroyed by ethanol fuel!!!
 
timguy said:
Excellent. Alaska has got to be on my wish list, certainly a place to get away from things. I have a couple remote camps in NW Ontario sure can't get enough of that either.
Question: Is the VRO still operating? They are typically destroyed by ethanol fuel!!!
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Yes the VRO is working. Seems to be doing fine. The motor sometimes smokes more than I feel like it should and if you pull the cover off the carbs there is what seems to be a lot of oil in the carbs but I’m thinking this is from the fact it’s not burning the gas properly. As far as Alaska goes it is a beautiful place. I was raised there and spent about 30 years of my life there. I love it but get tired of the long cold winters. Ironically I was born in Florida, lol, goes I’m a country boy at heart. Weather break tomorrow so taking the boat to do some troubleshooting.
 
Ha....interesting. I grew up on the farm and in the woods, love the seasons, but this has been an exceptionally long winter.
Could be a fuel delivery problem then....and also the oil cap vent is a common failure on these. The oil reservoir can build pressure, overdosing oil into the fuel system while at rest. If it smokes too much at startup, then the pressure has pushed oil onto the system. You can buy a new cap, or repair the old one. The vent cover can be removed, then you can clean and repair. I have also removed the vent components and reinstalled the cap. This is only a safe fix when the oil reservoir is protected from rain and possible flooding.
 
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Well fella's I got it figured out (i think). Ran multiple tests as advised by you all and found that the coil pack on cyl.4 is bad. So, i have ordered 4 coils, wires and plugs. I decided to replace all instead of just the one. Compression test showed 105 on all cylinders. I couldn't get timing and idle to adjust out right so i did the suggested cyl drop test and found the dead coil. Once that was realized trailered boat and came home to order parts. As soon as I get my parts and can install, I will let everybody know how it turned out. I very much appreciate everyone's suggestions.
 
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