help with a 73 Johnson 4hp outboard

[hobojoe]

Have gotten great advise from here before so let's try again. My brother has a 1973 4 HP Johnson outboard. It will run great when the top cowling is off. As soon as put the top on cuts down to around 1/2 speed and dies. What can I do about this or where are the adjustments. Like said sounds great without it.. We did not fish last year because would have probs getting started but started on like 4th pull this year, after cleaning plugs and new gas. Any help would be appreciated. Thanks Joe.

 

[nwcove]

sounds like you have an exhaust leak under the cowl, could be the base gasket or the exhaust cover plate. have a close look at those two areas for tell tale signs.

 

[racerone]

Running in a barrel ?----Do you have a fan blowing the exhaust away ?--------Possibly a plug lead shorting to the cowling latch too.

 

[F_R]

Agreed, it sure sounds like it is running in a barrel. It was designed to run on a boat, on the lake, not in a barrel of it's own smoke. The hood gathers the smoke and feeds it into the carburetor intake, smothering it to death.

 

[hobojoe]

Yes at the moment it is running in a barrel.but seems like every time we getvit to the lake it won't start. And wind up using trolling motor all night. Lol And there is more exhaust then I remember from past years, I could not remember fuel/oil mixture came here and saw a few posts that said 50:1 ratio and that didn't sound like what was running in past years but ran it . 2 gals gas said 5.1 ounces. But your saying should run fine on the boat in open water? Guess if it does not can just take the cowling off. And will look for leak around the gasket. As usual very good advice and help from this site thank you