1999 Johnson 50 Gas Leak from Lower Unit

[abchinchar]

1999 Johnson 50, J50PLEEA: Was looking for an air leak somewhere in the fuel line, and noticed the priming bulb would not harden. (Hardens fast when I disconnect the hose at the clip on the cowl.) Had my wife squeeze the bulb while I stuck my nose in the engine, and heard liquid trickling into the lake below my platform. Yup, clean yellow gas was cascading off the bottom of the fin on the lower unit with each squeeze of the bulb. It seemed to be exiting the lower unit somewhere just above the prop shaft beneath the planing fin. The entire engine and its lower cowls are clean and dry. So is the lower unit shroud exterior. All fuel line hoses from the tank to the carbs are new and tight. Compression reads just below 120, both cylinders. At this point I've cleverly deduced that this gas leakage accounts for the failure of the priming bulb to harden, but I am now mystified by the source of the leak. And since it doesn't appear to be a visible hose or filter, I am now filled with a massive, looming dread of some of the possible reasons for this gas leak. Any thoughts?

 

[oldcatamount]

Re: 1999 Johnson 50 Gas Leak from Lower Unit

Vro/fuel pump leak? Crack in fuel/oil manifold? Loose float bowl(s)? Does the motor run with it leaking like that?

 

[abchinchar]

Re: 1999 Johnson 50 Gas Leak from Lower Unit

Vro/fuel pump leak? Crack in fuel/oil manifold? Loose float bowl(s)? Does the motor run with it leaking like that?

Motor runs okay low idle, but dies out as I throttle up, which is why I just rebuilt the carbs and replaced all the fuel line. VRO has been carefully rebuilt. I can't find any leaks on or around it. Fuel/oil manifold is clean and dry. Carbs are tight, clean and dry. I've run it a couple of times to sync and link, adjust carbs, check timing, etc., but all without noticing the lower unit dripping gas. Was still getting the throttle bog, which prompted today's hunt for the fuel line leak. But it seemed to run okay at idle and low RPM. It's just that having a lot of gas dripping out of your prop shaft is sort of like finding ear wax in your navel. I think I'd rather fix THAT before moving back to the celebrated Johnson Throttle Bog At WOT. Hell, maybe that leak's been there a long time, and could be the reason for my JTBAWOT.

 

[oldcatamount]

Re: 1999 Johnson 50 Gas Leak from Lower Unit

Well, fuel is getting out of there somehow so, just guessing here but, it may be a float valve not seating. Which one is another guess but it would mean removal and inspection of both carbs.

 

[abchinchar]

Re: 1999 Johnson 50 Gas Leak from Lower Unit

Maybe so. I'll check the carbs again. But I'm also wondering how gas is getting down the inside of the lower unit. Am wondering if it could be something like gas being forced by the priming bulb through the carbs, through the engine and out the exhaust. Doesn't exhaust travel down through the lower unit? And what would be leaking that would push gas hard enough to get through all that hardware? I don't think that's supposed to happen.

 

[whalerdude24]

I am having the exact same problem with my 1999 Evinrude 40 hp. It can idle fine, but when I throttle it, it stalls out. Recently, it began to leak fuel from the lower unit. Any update on what happened or how to fix??