1975 Johnson 135hp dies under load

[dweber]

Hello,

My first post to the forum. I have a 1976 Johnson 135hp on a 1975 Starcraft 180ss that I bought two weeks ago. I am looking forward to restoring this boat. The motor idles and revs on the ear muffs in the driveway. Take it to the lake and the idle drops from 930rpm to 670rpm in the water. Motor has a hard time staying running when shifting into gear. Once in gear and running it will not stay running when advancing the throttle past 1500 rpm. The carbs have been cleaned and the compression is 120/cyl when tested in the driveway. Any suggestions?

Thanks!

Dan

 

[boobie]

Re: 1975 Johnson 135hp dies under load

How were the carbs cleaned? Will the spark jump a 7/16 " open air gap. Is the timer base advancing when you give it throttle? Has it been decarbed lately?

 

[dweber]

Re: 1975 Johnson 135hp dies under load

Disassembled, cleaned and reassembled. Did not put a carb kit in it, unless needed. They were pretty clean, no sediment or residue. I did run sea foam thru the motor for about 15 minutes. Replaced the fuel lines, they were cracked and leaking. I have not tested the spark or timing base yet will do tomorrow.

 

[emdsapmgr]

Re: 1975 Johnson 135hp dies under load

The idle rpm's should be set when the boat is in gear and is floating normally in the water. Set it between 650 and 750 rpm. You can't set it when on the trailer. If it is lower than 650 when in gear, it won't idle well and may die out.