max rpm 5100

[jgriner]

johnson 75 hp 1979 75elr79r

just got my tach hooked up, and all my motor would do is 5100 rpm. I have to keep my idle speed in gear set up to like 1100 rpms or it dies all the times

it also has no power, when i was trying to trailer it, I would give it some gas to pull up on the trailer it would hit somewhere around 4000 rpms and engine would just die.

I dont think its the carbs cause I cleaned it several times and rebuilt it once last year, and im have the same problems.

once last year after the first carb clean, it ran perfect for one day (sorry didnt have a tack then) but has been slacking in power ever since.

It has fresh gas
new fuel lines (last year)
cleaned fuel filter (last year)
New gas tanks (last year)
New plugs (last year)
timed (last year)
carbs cleaned and rebuilt (last year)
pumping the priming hose does not help
13x14 prop (i dont think its the prop cause it ran perfect one day on the same prop)
143-145 psi of compression in all 3 cylinders

thanks for all the help

 

[jgriner]

Re: max rpm 5100

one other thing, yesterday on the starter, the gear that pops up and down, stuck on me a couple of times. I want to take it off and clean it, how to you go about takeing it off, and would i clean it and put sometype of grease on it, or oil????

thanks

 

[jgriner]

Re: max rpm 5100

i got the starter gear fixed up,

 

[James R]

Re: max rpm 5100

Sounds like you may still have a dirty carb problem. If cleaning is not done correctly you can expect a repeat of the problem. While you are at it check the sparks with a spark tester and check the compressions. If the plugs are old they to can be a problem.

 

[jgriner]

Re: max rpm 5100

Sounds like you may still have a dirty carb problem. If cleaning is not done correctly you can expect a repeat of the problem. While you are at it check the sparks with a spark tester and check the compressions. If the plugs are old they to can be a problem.

the sparks have always been bright blue.... we also used a timing light and hooked up to spark plug wire when at wot, to see it flashed at a consent rate, and it did

im not a mechanic, but a freind and i took those carbs apart a dozen times last year only found trash in them the first time. My friend used to help a boat mechanic clean carbs when he was a kid,

we pulled them apart, and shot spray can carb cleaner through the jets, (we could not get some of the jets to come out) blow some air through them. he would blow air (with his mouth) to check the float was working correctly. then we would level the float with the carb body. did we miss anything
we never took the caps off, could that have been our problem? other than carbs what else could be the problem?

 

[hidef]

Re: max rpm 5100

You have to pull the welch plugs and soak the carbs. All kinds of crap can accumulate underneath them and plug those little passages.

 

[jgriner]

Re: max rpm 5100

k so how do u remove the plugs, and reinstall them, if i can find the left over rebuild kits tonight, i will clean them again tommorow. how long do i soak them in carb cleaner?

 

[James R]

Re: max rpm 5100

Use Gunk parts and carb cleaner Kit in a gallon can and soak for an hour. Follow instructions on the can. To remove plugs use a 1/8 drill and carefully drill a hole in the center of the plug. Dont allow the drill to go in past the plug. Use a hooked tool in the hole and pry the caps out. To fit the new caps apply a tiny amount of Red sealant to the outer edge of the cap and carefully tap them into place with a small soft face hammer.
Save the Gunk cleaner for any other carbs you need to clean.

 

[jgriner]

Re: max rpm 5100

red sealant is that like lock tight? or something else???

 

[cfauvel]

Re: max rpm 5100

red sealant is that like lock tight? or something else???

red sealant is a silcone based sealant, the different colors dictate the properties of the silcone, some have higher heat range, some have some solvent resilience .I am no export on these carbs so I don't know if the plug or orfices ever comes in contact with fuel or not (I doubt it since they are air bleeds), but silcone DOES dissolve with fuel...and it is a nasty mess if injested into the circuits...I know from experience. Stupid me.

I personally would use permatex #1 or #2, which ever hardens.

 

[jgriner]

Re: max rpm 5100

Aright cleaned the carbs, removing the welch plugs, and diping the carbs for 1 hour each... no improvements

Could this problem be the reeds? When I was spark testing with a timing light last year I knoticed that gas was blowing out of the reeds. The silencer box is always covered in gas, so is the inside of the engine housing, well so is the outside of the engine. Ive read time and time again, reeds rarely cause problems, and a boat mechanic told me that at 5500 rpms the reeds never close so blow back is always an issue, is that true? only about one reed per cyclinder I can see light through, I bought some used reeds off ebay, garenteed to work, they were in worse shape then mine and when I installed them, they did not help any.

 

[jgriner]

Re: max rpm 5100

bump

reed problem?