'73 50hp Johnson won't run in the lake

Just picked up 1973 50hp Johnson (50esl73 r). Had no idea how old the impeller was so immediately replaced it, good thing I did. It seems one fin was broke off. Put the muffs on in the driveway it fired right up. Let it run for 15 Min. or so. It ran smooth and cool. Read somewhere that muffs aren't the best way to check your waterpump. So I filled a 12" deep rumbermaid tub w/ water which easily covered the water intakes. Again Fired right up ran smooth an cool. Put it in the lake. It won't even start!<br />That is not until I tilted it up on the manual tilt so it was almost completely out of the water. Then it started. Drop it quickly back in the water dies immediately. And I mean immediately. I couldn't count to 3. Did this 4 times. Took it home put it back in the tub and of course it fired right up. Any Help would be appreciated.

Re: '73 50hp Johnson won't run in the lake

Put it back in the water try to start, if no go while still in the water check spark at plugs if you have fire take a squirt bottle with you full of 50:1 mix shoot it in the carbs and try to start it if it fires then dies check the fuel filter, is the primer bulb getting hard and staying that way? If it's getting fire and fuel it has to run mayby not right but it will start or try to. Check the compression make sure it is about the same in all cylinders, can't understand why it will run everywhere but in the water it dosn't add up. Let me know how it comes out maybe i can think of something else.

Re: '73 50hp Johnson won't run in the lake

Bass runner thanks for the quick reply.<br />I can't help but wonder if how deep I'm drafting in the water has something to do with this. It's hard to recreate the same conditions in my driveway. The motor is an additional 10" deeper in the water in the lake than in the tub. I can't see how that would matter though. The lower end on this motor doesn't quite fit into your "garden variety garbage can". So I'm trying to get my hands on a 55 gal drum. So I can see if depth is or is not a factor. Thanks again.

Re: '73 50hp Johnson won't run in the lake

Shiska,<br /> I'm no expert, but I was just thinking it could be your floats are not sitting right. I guess the only way to find that out is to check them. I can't think of any other reason off the top of my head, but I know, or at least 99% sure, the depth of the water has no part of it. Unless of course it was partially submerged, but I am pretty sure you would have noticed something like that. <br />Good luck,<br />Bro Chris...

Re: '73 50hp Johnson won't run in the lake

Here is something I wouldnt have been able to figure out either, except it happened to me. Is your boat sitting in the water, or is it on the trailer on the ramp when you are trying to start it. Sometimes the angle of the ramp is enough to mess with the flote level and not let the engine start.

Re: '73 50hp Johnson won't run in the lake

The one factor you're facing in the water that is not present when running with a flushette is "exhaust back pressure". Without that back pressure, it's possible to have a two cylinder engine running on one cylinder.<br /><br />What is the model number of that engine? It's important that we know exactly what engine we're speaking of.<br /><br />What is the compression readings of each cylinder? It should be 100+ psi and even on all cylinders. Is it?<br /><br />With the s/plugs removed, the spark should jump a 7/16" gap on all cylinders. Does it?<br /><br />The spark plugs (if the engine is indeed a 1973 model) should be Champion QL77JC4 or L77JC4 plugs, gapped at .040 .<br /><br />If the three items above check out okay, in all probability the carburetors are fouled and will require removing, cleaning, and rebuilding.

Re: '73 50hp Johnson won't run in the lake

A outboard will run in water up to the powerhead as long as you don't injest water in the carbs. This is a wierd one, like already stated check the compression, are you sure none of the wiring to the ignition is shorting out when you put it in? This is a real brain strain, has to be something so obvious that we can't see it.

Re: '73 50hp Johnson won't run in the lake

Ditto-what Joe said.

Re: '73 50hp Johnson won't run in the lake

Sorry it took so long to get all the info but the weather was bad. Not to mention family stuff.<br />Here they are.<br />Model#--50ESL73 -R<br />Plugs---QL77JC4<br />Gap-----.040<br />Compression 75 lbs. upper- 74 lbs. lower<br />Spark jumps a 7/16" gap fine. Tried starting the motor removing one plug wire at a time. It started with lower plug wire removed but not when the upper was removed. While doing this I noticed the lower float bowl was wet. Got a flash-light and sure enough there was a puddle of gas accumulating under the lower bowl. That was enough for me. I pulled the carbs. Haven't tore into them yet. I will tonight. My question at this point is-does the low compression mean a complete rebuild right now? Or can it wait. Opening day is week away! Thanks for everything, shishka

Re: '73 50hp Johnson won't run in the lake

I wouldn't go rippin it apart just yet. Get it running then do a thorough decarb job and retest. You might even borrow a different compression guage in case the one you have reads low. Even if the compression does not come up I wouldn' do anything if it runs well.

Re: '73 50hp Johnson won't run in the lake

That happened to me on my 200hp.<br />It was deffinently the back pressure.<br />It would start right up on the muff's all day long, but NOTHING in the lake. Unless i had it tilted almost with the prop comming out of the water.<br /><br />So anyways..I seemed to fix it by cleaning and putting in a carb kit (needle vale, gaskets, float) on each of the 3 carbs.<br /><br />hope this helps

Re: '73 50hp Johnson won't run in the lake

Just want to thank everybody again. For all the help and insight. UPDATE! As Joe said, the motor was running on one cylinder, but not because of the carb as "I" thought. It turned out to be a bad ignition coil. When I tested with the spark tester I never let it turn over long enough to see how sporatic it really was. Bought A new one and know she's firing on both cylinders nice. Before I found the bad ignition coil I tore into the carb. It didn't take long to out someone else was here not long ago. Everything was brand new. The only reason it was leaking was a few loose bolts. Quick question-when I did the compession test I did it by the book, removed both plugs, disconnected the stator wires and throttle wide open. 75 lbs both cyl. I did it again saturday but this time left the other plug in. Compression 115 lbs. both cyl. Whats up with that? Is that normal? Which one is right? Thanks again--shishka