1950's Johnson breathing problems?

[55Crestliner]

I've been doing a little work on my '57 Johnson 18 horse the last couple days, and I got to thinking (I know, bad thing). How in the world does this motor get air to the carb? The hood is so well sealed up, with a gasket at the bottom, gasket for the face plate, and a plate where the pull cord comes out. Seems to me that the motor would starve for air.<br /><br />I know I can answer my question by taking the hood off next time I go out, see if RPM's go up, but I was curious if some of the more experienced ones here can tell me about this. <br /><br />Did they take the hoods off for racing? Make an air inlet? Didn't bother? Do tell. <br /><br />55 "always after more speed" Crestliner.

 

[DJ]

Re: 1950's Johnson breathing problems?

The air comes in through openings at the base of the cowl, just above the clamp bracket.<br /><br />If your engine runs better, with the cowl off, you have an exhaust leak. Probably from the engine exhaust cover, or the powerhead base gasket.

 

[55Crestliner]

Re: 1950's Johnson breathing problems?

Well, that's kinda my point, there are no openings in the base of the cowl. None. <br /><br />Motor is running good, acually great, I'm just always wanting more.

 

[DJ]

Re: 1950's Johnson breathing problems?

55,<br /><br />You'd be surpised at how much air can come through very small openings.<br /><br />As far as wanting more. More air won't help. Those engines were designed that way. Allowing more will only result is lean running conditions and piston melt down.<br /><br />If you want a "race" engine, there's more to it than allowing more air.

 

[Chinewalker]

Re: 1950's Johnson breathing problems?

Those "seals" are to keep sound in, not air out. They do a fair job of it on the sound end (listen to a '54 Evinrude 15 that lacks the silent treatment vs. a '55 with it!), but it is far from air tight. Take your cowling off, flip it over and try filling it with water. It'll leak like a seive...<br /><br />- Scott