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1992 Evinrude 120 HP Power Problems

J

jdsmith61

New member
A few years ago my boat started to lose power when the outside temp was very high ie sometimes my partner would have to set on the bow to get it to plane off when the weather cooled down it would work fine I do a lot of night fishing. The next year it was little worse over a period of about 4 to 5 years it got worse to the point where you had to help it plane off all the time it always ran smooth I just thought it was wearing out I have put many hours on it. I had decided to rebuild it myself so I replaced all pistons had the cylinders checked by a marine shop replaced all the bearings and seals got it put back together and timed it I followed the book and when I took it to the lake for a test run it ran the same as it did before so i broke down and took to a marine mechanic that all of my friends said was the best around he keep it for about 5 months and called me and said he had it fixed. I took it home because it was very cold outside in the spring I took it out however it ran the same so i took it back to him he told me that he would get it fixed after 8 months he said he had it fixed he had to replace one of the carbs it did run better however it has problems planning off and about 4900 to 5000 rpms is all it will turn when it ran right you could turn 6000 easy.
sorry this is so long I know it has a weird problem just cant seem to get it figured out any help would be greatly appreciated. Thing that I have tried replace carbs replaced reeds new power pak checked timing fuel lines rebuilt VRO it idles very good and runs smooth just weak.
 
Run the motor on a dynomometer.---------------If it puts out the proper power there is something wrong with your boat.----Perhaps it is water logged.
 
racerone said:
Run the motor on a dynomometer.---------------If it puts out the proper power there is something wrong with your boat.----Perhaps it is water logged.
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Yes I thought of that however the mechanic that looked at it told me to start with that he had put some kind of prop where he backs the boat in what I call a small pond behind his shop and that the 120 hp motor should turn that prop 5500 rpms and that he could not get it anywhere close to that which also leads me to believe that he knew that it wasn't fixed when he told that he though that it was because he could have checked it again
 
A test prop is the same as a dynamometer.-----Find another mechanic or do your own trouble shooting.---------Check for top notch spark on each cylinder.---------Does it jump a gap of 7/16" , yes or no ?----Do a compression test and report your actual values.------------Perhaps check the flywheel key as well.
 
5 months and 8 months ..over a year at this "mechanics" shop and he still cant figure it out? If you arent willing to go at it yourself...please do not take it back to that guy.
 
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