1975 johnson 70 hp

[sparkyl300]

just bought this boat from my brother, I used it several times last year so I know that there are a few problems. The motor idels well and runs great at wot but floods out at trolling speeds. I'm sure the carb needs cleaned and rebuilt, any other things I should check. Any help is appreciated.

 

[HighTrim]

Re: 1975 johnson 70 hp

Frequent trolling can sometimes cause carb troubles. Im sure it is in need of a bath (clean and rebuild). Make sure you get at those high and low speed jets . Tashas Daddy or FR has a pic of the tools you will need. A decarb should follow.

(Compliments of Tashasdaddy)

i think i would invest in a can of seafoam, in a portable tank, mix 3/4 gallons of premix gas, an 3/4 can of seafoam, (assuming you don't have the vro connected). Put the remaining seafoam in a spray bottle, run the motor up to temperture, remove the plugs, one at a time, spray some seafoam into each cylinder and replace plug. let sit 15 minutes, remove the air silencer from the carb while waiting, restart motor, and spray seafoam into each carb, until it start to stall. repeat till seafoam is gone. run out the rest of the gas. it is going to smoke like it is on fire, and drip goo on the ground. replace the plugs with new ones, and then do the compression check again. this procedure burns the carbon out of the motor and been known to free up rings, and increase compression. let me know the results.

 

[doggonegoose]

Re: 1975 johnson 70 hp

Hi Have you checked the compression. At fast speed it will run good, but as you slow down the compression will drop to making it idle badly or quit altogether. Hi and low speed orfius are non adjustable. I might be wrong, have been before according to wife. I an having same problem with mine and the shop said it was a tired motor. Low compression. Am looking hard and serious about putting any more money into it.Just spent $225. putting a new water pump in. Runs good from about 1/4 to full speed. 28 miles per hour on a 18 glastron. Maybe should sell boat and motor. Any good offers. Any one handy putting rings in would have a good boat and motor. Would need a couple days notice to put motor back on. Had it off to put on my pontoon. Forgot it has tilt and trim which work good. Only problem is they in wrong spot for the toon. The hyd. motor is past the side of motor mount and acts like a anchor by catching water and spraying all over. Works good on glastron . Comes with all controls and steering wheel and cable. Two adjustable seats and livewell seat on top. Has bilge pump and pump in livewell. If interested, come try it out. Am only two miles from lake. Remember money talks. Thank You

 

[doggonegoose]

Re: 1975 johnson 70 hp

Hi Just read your reply. Where do you get the seafoam from. Will give it a try. Thanks

 

[HighTrim]

Re: 1975 johnson 70 hp

One of the guys on here from the states could better answer that for you, Im unfamiliar with the store names.