My 1958 johnson 7.5 won't speed up

[Aydelott]

My 1958 johnson 7.5 won't speed up it starts on the second pull idles fine but when i turn the handle to shift gears it dies an when I turn it to fast it just chugs along real slow this is my first outboard so i dont know much about them I just got it And I found water in the gear oil so I replaced everything from the power head down it cost me over $600 so I'm hopping this is a cheap easy fix i dont know much about carbs.

 

[MikDee]

Re: My 1958 johnson 7.5 won't speed up

Take the cover off, and look to see if your carbs are opening fully as you give it throttle, then look closely under the flywheel to see if the mechanical spark advance plate is also moving as you give it throttle.

 

[HighTrim]

Re: My 1958 johnson 7.5 won't speed up

Yikes, 600 bucks where did you get your parts!

Could be a couple issues. First, with any new outboard, or issue, check compression.

Next, get a spark tester, set the gap to 1/4" and test both cylinders. Spark should jump the gap with a bright blue ZAP!!
You can also run it, and pull off 1 plug wire at a time, using insulated pliers of course, or have the wife do it You should hear a noticeable drop in RPMS. IF not, that cylinder was not running.

Could also be fuel delivery issue. The carbs are quite simple on that motor. Change the fuel line while you are at it. Soak clean and rebuild and you should be good to go.

Have the coils be changed? Ignition gone over at all? Was it a shop that you spent 600 dollars at?

 

[racerone]

Re: My 1958 johnson 7.5 won't speed up

Could be a bad shock absorber in the lower unit too.------Wish I could find folks who would spend that kind of money.---You should be able to buy one with a 1 year warranty for that kind of coin.

 

[HighTrim]

Re: My 1958 johnson 7.5 won't speed up

Could be a bad shock absorber in the lower unit too.------Wish I could find folks who would spend that kind of money.---You should be able to buy one with a 1 year warranty for that kind of coin.

Very good point, was meaning to mention that as well. I have seen motors with such bad shock absorbers they will not even start. Ill assume the gearcase rebuild for 600 would cover that though?

 

[Aydelott]

Re: My 1958 johnson 7.5 won't speed up

Next, get a spark tester, set the gap to 1/4" and test both cylinders. Spark should jump the gap with a bright blue the spark plugs were deffinaley shot one was mashed against the nipple the other had 32nd of carbon build up on my way to get some now were I saying to put. A 1/4 in gap between the nipple and the arm thing sorry about my lack of knowledge I'm a machinst not a mechanic thanks

 

[HighTrim]

Re: My 1958 johnson 7.5 won't speed up

No the 1/4" gap is for the tester. That gap mimicks compression in the cylinder, to ensure the ignition is up to snuff.

The spark plug gap is 030. Are you getting Champion J6C plugs? They will come pre gapped at 030

 

[racerone]

Re: My 1958 johnson 7.5 won't speed up

The one sparkplug with a closed gap is a big concern !-------Check for a loose bearing / connecting rod.

 

[HighTrim]

Re: My 1958 johnson 7.5 won't speed up

Or maybe wrong plugs in there? What was in there?

 

[Aydelott]

Re: My 1958 johnson 7.5 won't speed up

The one sparkplug with a closed gap is a big concern !-------Check for a loose bearing / connecting rod.

I think that might have bee. Because it didnt have a washer that spaced it back out a little bit the other plug had it I got it hitting high rpm but in doing so I took off the plastic cover with the lean rich printed on it an I have those two needles all out of Wack I didn't think to count how many turns I backed them off till it was two late I seem where someone referred two a post a bout how to set them but I can't find it and it is still dieing when I put it into shift mode thank u guys for all your help

 

[HighTrim]

Re: My 1958 johnson 7.5 won't speed up

To start, set the low speed, top one, 1.5 turns out from gently seated.

The high speed, bottom one, 3/4 of a turn out from gently seated.

Then tune on the water. Start with the high. Go WOT, and slowly, in small increments, lean the needle, clockwise, until it want to die or backfires, then back it back out 1/4 turn or so.

The go down to an idle and do the same with the low speed needle.

 

[Aydelott]

Re: My 1958 johnson 7.5 won't speed up

U have know idea how much I appreciate u guys I cant even put it at slow it dies if I go any past start I can't even but it into shift with out it dieing so I have to start it in gear and i dont know why

 

[HighTrim]

Re: My 1958 johnson 7.5 won't speed up

Follow the steps in my post 3

 

[nwcove]

Re: My 1958 johnson 7.5 won't speed up

has the carb been rebuilt? pressure tank or converted to fuel pump? needles should be set .....top needle 1.5 turns from gently seated, bottom needle 3/4 turns from gently seated. those are generic settings for start up, and will need to be tweaked . with that being said, and as mentioned, compression test! then do the drop cyl test.

 

[Aydelott]

Re: My 1958 johnson 7.5 won't speed up

It seems to have good compression but I'm not sure I'll have to borrow a tester. I really don't know what the previous owner had done to it. He did convert it from a pressure tank to a diaphragm also it had water in the gear oil so I replaced all the seals the prop housing ,gear housing, impeller housing all the gaskets an seals also the driveshaft was missing the porclin thing above the spring that'
holds the seal where the drive shaft enters the power head that being gone wore a huge ring in the drive shaft so I got all those parts the spring in the gear box
That holds it In gear was pushed over to the side so it was not even working also I got everthing from marine engine.com an crowleymarine.com I had issues with both places sending me used an broken parts all that with shipping was the 600 I picked the motor up for 300 I thought It was a good deal based on what they went for on eBay but my wife is getting annoyed with me putting all this money in it that's why I don't just take it to a shop so I really appreciate all your guys help the old owner must have ran it hard and put it up wet it's a amazing it started right up I still don't understand why it dies if I turn it to shift this is my first out board so I really didn't know anything about them till I started takeing this one apart

 

[Aydelott]

Re: My 1958 johnson 7.5 won't speed up

Chris both cylinders are right at 75 on the compression test and both have good spark I'm going to run some seafoam threw if the cylinders look pretty gummy and slot of carbon buildup

 

[Greg O.]

Re: My 1958 johnson 7.5 won't speed up

Are both sets of points set at .020 inch? Also the cam that operates the throttle needs to be set so it just touches the throttle when it is in line with the line on the right side of the cam as you are looking at it. Your compression of 75 isn't too bad, especially since both are the same. It almost sounds like a dirty carb.

 

[HighTrim]

Re: My 1958 johnson 7.5 won't speed up

yeah go through fuel system, and check linc n sync as mentioned above here.