not going very good

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bigd5977

Seaman
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Jul 19, 2011
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ok, i have a Johnson 75ELR77s motor ,, it has spark, timing is good, getting gas, when it's out of water & has the earmuffs on it runs great,, throttles up with no problem & when in gear it throttles up with no problem,, when it's in the water,, it throttles up good,,, BUT, when in the water & i put it in gear,, i can only get it up to a high troll most of the time,, as soon as i try for more power/full throttle,, it dies & really takes some work to get it finally up & going full throttle,,, WHAT COULD POSSIBLY BE WRONG ???
 

oldcatamount

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Re: not going very good

Sounds like it's dropping a cylinder. Check the compression and re-check the spark. Sometimes it's as simple as putting a new set of spark plugs.
 

bigd5977

Seaman
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Jul 19, 2011
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Re: not going very good

compression is good on all 3 cylinders,, 120,, 120,, 115 & spark plugs are all new
 

bigd5977

Seaman
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Jul 19, 2011
Messages
59
Re: not going very good

also,, why would it run great out of water with earmuffs on it & water hose attached & water going thru the system,, compared to being in the actual water/lake ,,, what is the difference ?? besides the force of the propeller against the water to make the boat move,, it is something to do with the power in the propeller area that would kill the motor or make it act like the motor is flooding out,, i'm very mechanically inclined,, but this has me stumped ,, like i said,, in the water u can can throttle it up & down with no problem,, IN NEUTRAL ,, but put it in gear & it's whole new story
 

oldcatamount

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Re: not going very good

The difference is in the "back pressure"from the exhaust. On the muffs, there is no back pressure and in the water there is. Have you cleaned the carbs lately? You have good compression numbers, and good ignition, so the next thing is fuel delivery. It's entirely possible you have a dirty carb (or two) that are starving the motor when you put the throttle down and the motor would still run ok on the muffs. Check the entire fuel system for air leaks (loose clamps, cracks, etc). Has anyone been "adjusting" the carb(s) linkage? That could be another area to investigate. The carbs have to function at exactly the same time so the linkage adjustments are crucial.
 

Playantony007tm

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May 29, 2023
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did you ever figure out the issue? I have the same exact motor and same exact issue, runs great on muffs but when I put it in the water it bogs and dies as soon as you give it throttle. I also figured out I can bump the choke with the key as I'm throttling up and it will allot it to run and get up to wot.
 

saltchuckmatt

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Jul 19, 2019
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Fuel pump or carb clean/settings not done properly. This assumes compression is acceptable. Full diagnostic of this motor is needed.
 
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