Power Loss

I have a 1973 Evinrude 50 Hp motor. A couple of weeks ago, my boat started and performed as usually. Then the time to head back to the dock, the boat was slow coming out the hole. Finally reaching plane, it became to loss power. Since then I have changed the spark plugs and taking the carburators apart and cleaned them out. The motor will start fine, idle fine and will start off slowly, but as soon as it reaches speed of 25 mph, then it losses power below speed of 10 mph. Even after coming off the throttle and trying to restart, the boat will not exceed 10 mph. After allowing to sit, the same result will accure. <br /><br />Any advice is welcome.<br /><br />Thanks<br />Ed

Re: Power Loss

Ed, welcome to the forums.<br /><br />Couple things you need to do.<br /><br />First, make sure the engine is NOT overheating. At idle, lay your fingers on the flat area on top of the engine just forward of the head. You should be able to keep them there for several seconds with out having to pull them away. You will know if it's really hot.<br /><br />Take a compression test and make sure the cylinders are in good shape. Should be within 10 to 15% of each other on compression.<br /><br />Check your spark. Each spark should jump at least a 7/16" gap with a hot white spark.<br /><br />Check your fuel lines are have not gotten hard and are not sucking air at the connections.<br /><br />Primer bulb in good shape and the tank venting OK?<br /><br />Check the above out and let us know what ya' find.<br /><br />Keep us posted....thanks.

Re: Power Loss

I am having a loss of power problem with a 1998 48 hp spl Johnson. the problem was intermitant, but has become full time. When I first start it, it runs fine, as soon as it hits 4100 rpms it starts to run very badly, but will idle fine. The motor will not go past 3000 rpms after this, until it is shut off, then it will go to 4100rpms again and then lose power. I have changed plugs, changed fuel, changed and/of check fuel lines.<br /><br />Does anybody have any ideas?

Re: Power Loss

Do you have have a fuel/water seperator in the gas line,I would also change the in line filter. Is the gas tank vent closed? Could also be a power pack or coill problem also,

Re: Power Loss

Originally posted by EdW02:<br /> I have a 1973 Evinrude 50 Hp motor. A couple of weeks ago, my boat started and performed as usually. Then the time to head back to the dock, the boat was slow coming out the hole. Finally reaching plane, it became to loss power. Since then I have changed the spark plugs and taking the carburators apart and cleaned them out. The motor will start fine, idle fine and will start off slowly, but as soon as it reaches speed of 25 mph, then it losses power below speed of 10 mph. Even after coming off the throttle and trying to restart, the boat will not exceed 10 mph. After allowing to sit, the same result will accure. <br /><br />Any advice is welcome.<br /><br />Thanks<br />Ed

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Ed<br /><br />I have a 1975 Johnson 50 Hp motor,and had similar problem this time last season. Ended up being the power pack.