1977 70hp Johnson. Can i fit idle needles

[dcr42t]

I have rebuilt a 1977 70hp Johnson. Have got the motor running ok on muffs but once i put it in water, it doesnt want to start, and when it does, it wont idle any lower than 1300 -1500 rpm. Cant get it to idle, just stalls out.

Spark is good
100psi each cyl

The idle jets are 32's. I cant see any restrictions in the carbs. I have removed the welch plugs and all ports are clean.

What id like to know is, can i fit some adjustable needles to these carbs? Im sure ive read you can somewhere, but cant find the post. id like to try richening up the idle and see if this solves my problem.

If not, i guess i just try and get some 33 or 34 jets? Is there a chart with part numbers for these jets somewhere here?

The only other this i think could be happening is a small amount of water getting in through the exhaust sandwich plates. These have all new gaskets though so i will start with the carbi's.

 

[fireman57]

Re: 1977 70hp Johnson. Can i fit idle needles

Have almost the identical engine. the .32 jets are the right ones. Check your spark with a spark tester, it should jump almost a 1/2" with a bright blue spark and a snap to it. If your spark is okay go to O'reilly's auto parts and get some clear fuel line. They have it for lawnmowers and put it on from your fuel pump and also the small lines to your carbs and see if you are getting air in the line. The lines are a32nd smaller than what the specs call for but they did the trick for my engine. Seem to seal better and didn't need any clamps. If you are still getting water in the exhaust side then you need to pull it off and change those gaskets or see why it is getting in there. Plugs can't burn water. If you are sure that it is coming in there then you have no choice but to fix that. If you are still getting water then change your head gasket.

 

[dcr42t]

Re: 1977 70hp Johnson. Can i fit idle needles

Thanks for the quick reply.
I have just bought a proper adjustable spark tool, so i will check that properly. When i get these carbis back together i will give the clear fuel line a go.

The motor will run at high idle no worries and will continue to do so, but when i try to bring it down to an idle it will stall. There is still plenty of fuel in the carbi when this happens which makes me think its not sucking air, but i will check anyway.

 

[F_R]

Re: 1977 70hp Johnson. Can i fit idle needles

The exhaust baffle plate is probably warped in the ports area. Gaskets alone won't fix it. You gotta deal with the warp. Replace the plate is best way. Unless you can resurface it. That water will destroy the powerhead.

 

[fireman57]

Re: 1977 70hp Johnson. Can i fit idle needles

What F_R said. It will run at high rpm because it will keep up with the small amount of water but you are looking for BIG trouble if you keep running it this way. Get rid of the water leak and everything else will probably be fine.

 

[dcr42t]

Re: 1977 70hp Johnson. Can i fit idle needles

Hopefully the inner exhaust plate is the problem, because ive been scratching my head over this.
Will let you know what i find. Wont be able to get back on it for a couple weeks though because of work. Gaskets on order.

What is the best sealant to use on the gaskets? I did read that some use a 3M product, but does it withstand high temps? I used hylomar when i assembled the plates, but it wouldnt have taken up the gaps very well if it was warped.