1973 50 hp evinrude (50373r) bogs down past half throttle

[jake83]

So I took the rectifier out and cranked, still no spark. Went ahead and put the old stator back in just to see. Spark came back on both cylinders with new coil packs. Put new stator back on and no spark. Strange thing is that the new stator ohms out within spec and old one does not. Oh well, it doesn't get more conclusive than that. Definately a bad stator right out of the box, I don't care what the ohmic value of the coils are, it just doesn't work. Gonna snatch up a new rectifier for 30 bucks at Napa and return the new stator for one that works. I found a post on this forum that was titled "bad rectifier?" and there was some good info that explains how a bad rectifier can cause the stator to overheat and cause coils to start leaking. Still doesnt quite make sense to me since the rectifier has nothing to do with ignition, but hey, 30 bucks for some peace of mind aint bad. Hopefully it's all downhill from here. I would love to get this thing up and running ......I wanna go fishing!

 

[ondarvr]

You can get a rectifier at Radio Shack for about $5.00, I've used them several times and they work well.

 

[jake83]

Well I just paid 30 at Napa. Damn. At least the bolt holes line up

 

[jake83]

Got the new stator in today. Woo hoo! Got it all put back together and spark is back and stronger than ever. Seems to be idling really high but that is also on muffs. I will take it on the water as soon as I can and let y'all know how it worked out. I have a feeling carbs will need a little readjusting but I have been looking in to how to adjust them and it seems pretty straight forward. Hopefully all is well and I can move on to my cooler/livewell project. Fingers crossed......

 

[jake83]

Put the boat in the water yesterday. Planed out then same ol bogging down. Tried to adjust carbs on the water while idling. Top carb screw adjustment did nothing. Pulled top plug boot and no effect. Did get shocked a little though (rubber handles leaked through my pliers just a bit). Pulled bottom boot and motor died. So I am running on one cylinder.
I pulled boat out and cleaned carbs with carb cleaner and air compressor (no rebuild kit yet) and reinstalled. I seated the needle valves then backed out 1 1/2 turns. Same issue pulling plug boots. Pulled plugs and top ceramic is dark brown and bottom plug is a light tan. I rechecked compression and top is 155 and bottom 165. I swapped the two plugs and still only bottom cylinder is running (pull bottom boot and motor dies). I pulled carbs off again and inspected reed valves and no broken pieces or anything like that. (I am still learning or I would have done that the first time).My inline spark tester shows great spark at 1/4" on both cylinders. So it's gotta be a fuel issue right?
So I adjusted the needle valves starting at 1 1/2 based on the Joe reeves sticky. I double checked manual and it says to start at 3/4 turn. Is it possible that even though they are even, that with the valve being to far open on the bottom carb would draw all the fuel from the top before the top can take it. The fuel line runs to the top carb first. I think maybe I'm going to slap the carbs back on real quick and close off bottom needle valve and see if I can get top cylinder to fire off. No success with that then I'm going to rebuild carbs the right way. No success with that and I am out of ideas. Anybody wanna chime in here?

 

[AlTn]

when you clean the carbs with carb cleaner and air compressor, would you describe how much disassembly you do and exactly what you spray the carb cleaner and compressed air through?...are you removing the orfice plug < main jet > and cleaning it, or are you cleaning it in place < still in the float bowl >?

 

[jake83]

I completely rebuilt the carbs today. Pulled all Welch plugs, found the hole directly behind the slow speed needle valve appeared to have some varnish so ran a bread tie through it and blew it all out with carb cleaner and air. I removed all jets and float the first time and obviously when I rebuilt it. Had to bend float a little to get it parallel on both new floats.
Got everything put back together and still only had bottom cylinder running. I swapped the coil leads on the power pack and put boot from top coil on bottom cylinder and that cylinder still ran fine. Put it all back to normal when done. I turned the butterfly valve while running and I can see gas entering both carb throats. Pulled top plug and it's slightly wet. Tries spraying a spraybottle of gas in top carb to no avail. I am sooooo discouraged right now. I thought that bit of blockage was it! I don't even know what to do next. Since I can see fuel entering carb throat and I know spark is good I would think bad compression but it has been testing fine. Maybe stuck reed valves...... but the plug was wet. Hmmmm. Fuel spark and compression sure is getting complicated.

 

[AlTn]

instead of "inline spark tester set to 1/4""...try checking with an open air gap spark tester set at 7/16" gap..< these testers are available at most auto parts stores ~$10 >...make certain it is grounded well....I check for spark with the plugs out making certain the spark isn't in direct line with any fuel mix that may come out of the spark plug hole....I have checked with a screwdriver inserted into the boot and held approx. distance from a head bolt or other ground...difficult to get the exact distance with this method tho'....just doing this to make certain that the ignition system isn't a factor...just to rule it out with some certainty

 

[jake83]

It is an adjustable spark tester. I set it to 1/4" per the manual but I can widen the gap if you think that it is necessary. I ripped the reed boxes out last night but tore the gasket all up in the process so I've got to go get some gasket material before I can reassemble everything. Then I was thinking of swapping the two reed boxes just to rule them out. Once I put it back together I can retest with the air gap set wider.

 

[jake83]

Just got back with gasket material. Gonna go trace out a pattern and make a gasket up. I sure wish the marine parts stores were open on Sunday and save me some hassle. Oh well. I'll let you know what happens

 

[jake83]

Got the reed boxes swapped out and made me a gasket. What a pita. Anyway, tested spark with the gap stretched to 7/16 and it had spark on both cylinders. Top cylinder still not acting right. I can get it to run on bottom cylinder alone no problem. I can get the top cylinder to run alone for a short amount of time but it is soooo weak. Doesn't even sound like the same motor. Also a new problem arose, once I prime it up it will run a minute or two then the rpms spike and motor quits so I'm guessing the fuel pump. If I pump the bulb every once in a while it stays running. When I ground out top plug I can hear a definately difference but I ground the bottom plug and motor dies everytime. With compression testing okay, could a clogged exhaust port cause a weak cylinder? I haven't pulled the exhaust cover or anything yet , should I?

 

[jake83]

No Title

 

[AlTn]

good..ignition eliminated...not likely the exhaust would be plugged to that extent, however by removing the exhaust covers you can examine the piston skirt and rings on ~ 1/3 of the side of the pistons..skirt and rings on that upper cylinder need to be checked on that upper cylinder as they can affect crankcase pressure....be prepared to pull the powerhead if any of the exhaust cover screws break off in a location that would be hard to drill out with the ph in place...upper crank seal showing any sign of leaking? ...sure seems to be more of a mechanical problem now rather than a carb/ignition one

 

[jake83]

Upper crank seal seemed alright to me, I looked at it when I had the flywheel off to replace stator and saw no signs of an oil leak or anything. So is it worth pulling the exhaust cover? Is there anything I can do to help bolts from breaking off if/when I do?

 

[jake83]

No Title

Upper crank seal seemed alright to me, I looked at it when I had the flywheel off to replace stator and saw no signs of an oil leak or anything. So is it worth pulling the exhaust cover? Is there anything I can do to help bolts from breaking off if/when I do?

 

[AlTn]

heat the area and loosen then tighten the screws as little as 1/8th turn at a time...when one begins to feel tight..stop... try some penetrating oil on the threads and tighten it back up....use heat and try loosening it again....patience is vital, but if a screw is really damaged no amount of caution will prevent it from breaking off..let's hope if any do break they become more like a stud and the exhaust cover can be worked over the screw and enough of a "nub" remains that some vice grips can be used to remove the rest of the screw....better yet...hope all of yours come out freely

 

[jake83]

Thanks. I'll give it a shot after dinner

 

[jake83]

No Title

So I finally was able to get another look at it. The bottom two bolts on the cover plate seemed to be the toughest so I started with those. The good thing was they backed out somewhat freely.........until they backed in to the motor housing. Do I have to pull the power head just for these two stupid bolts?

 

[racerone]

Look for issues with the fuel pump.--Could be a ruptured diaphragm.

 

[jake83]

Would the fuel pump cause one cylinder to run worse. If not I need to get to the problem before I address the fuel pump issue. I have never had a problem keeping the motor running till today. I have also squeezed the primer bulb while running and it makes no difference (well in how it runs, not how long). Just trying to put it all out there. But any advice on getting the bottom two bolts off the exhaust plate without pulling the motor?