Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: 1981 Johnson 70 carb adjustment

Posted by BillTano on 09/15/18 - 8:55 AM
#1

Hey everyone,

Had three fantastic weeks with my 1974 Montauk in Lake George this summer. At one point it was starving for fuel, and would not run wide open. I took jets out and sprayed carb cleaner in many times which ultimately fixed the problem. It also has intermittently not idled great. The engine has new coils, wires, and fuel pump. I ordered rebuild kits for all three carbs and took them apart as it was time. After soaking them in carb cleaner, I installed new needle, seat, float, idle and main jet orifices in all three carbs. My question is other then setting the floats correctly, syncing the linkages to ensure all butter flys are eqully closed, and backing idle needle out one turn per the rebuild instructions, is their any other carb adjustment I can make???

As far as I can tell/read the only other adjustments are on the cable linkages / cam stop screws for the idle positon and wide open position. Any help would be appreciated. The manual spec calls for that adjustment to be made in water, with engine warm, while in gear. I dont live near water so trying to do all I can beore I tow to ramp.

Thanks in advance,

Billy

Posted by BillTano on 06/22/23 - 5:36 PM
#2

Just wanted to post I found the cause of my Johnson 70 dying when throttling up to go on plane from idle, and the irrational idling I have been dealing with for quite some time. The timing advance arm was getting hung up under the flywheel when the throttle was increased. When throttling down the timing arm was hanging up and therefore not retarding. Causing it to stumble and stave for fuel out of the hole. Hitting the choke got me through that rpm range, and then ran fine. But caused it to not idle down consistently, and stave for fuel out of the hole.

Now that I fixed that my 1981 Johnson 70 is running better then ever.

I have been chasing this problem for years. A couple mechanics even looked at it and could not figure it out.

Hope that helps someone.

Posted by Joe Kriz on 06/22/23 - 5:49 PM
#3

What was the fix?

Posted by BillTano on 06/23/23 - 6:22 AM
#4

Good morning Mr. Kriz,

I’m going to Seatrial this weekend. On the muffs in my driveway it is idling, throttling up and down better than it ever has since I have owned the boat. Will update once I run it on the water. I’m pretty sure it did.

I sprayed lube under the flywheel as I found a blog where someone said there is a bushing under the flywheel that gets corroded. I also took apart and cleaned the shift control assembly, Morse control, and cleansed all the old grease and regreased.

It’s running better than it ever has. Will repost after I run it on the water.

Billy

Posted by BillTano on 07/12/23 - 3:24 AM
#5

Morning everyone,

Just got back from Lake George. I put the timing light on my Johnson 70 and ran it at WOT as dusk. Timing was at 22 degrees. Adjusted it to 17 degrees.
It is running better then it ever has?

It is idling and pulling onto plane better then it ever has.
I was adjusting based on the timing being off, which is why I could never get it to idle correctly and consistently.

Between the combination of the timing advance hanging up under the flywheel, and the timing being off was my problem.

Hope this helps someone!

And thank you to everyone for their help to all my questions to keep my whaler running

Billy