89 Mercury Classic 50 won’t open up

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,446
It would have been nice to know about that little Tidbit...
 
Joined
Jul 12, 2024
Messages
23
Fuel pump diaphragm ruptured ?----Exhaust tuner plugged ?-----Post actual compression values.
Got another small update, slow progress is better than no progress !
I finally pulled the lower unit back off last night and checked to make sure that exhaust tuner wasn't plugged, and it appeared to be wide open. Pulled the carbs back off and installed the venturi in both of them, everything is back together now, going to go for a water test tomorrow evening. Max timing at cranking speed with plugs out seemed to be about 33 degrees, I tried to back that off a little but 3 turns of the screw in didn't change it at all. That's confusing to say the least. One last thing I noticed, I connected my timing light to each plug wire again at idle. 2 cylinders are showing a super fast rapid fire flash, and the other 2 are a slower normal looking flash. This is consistent with no misses when revving. Not sure why it would be like that but going to water test and see how it does.
 

redneck joe

Supreme Mariner
Joined
Mar 18, 2009
Messages
10,919
I can assure you I'm not your average bear, I will figure this thing out eventually and post the results right here for everyone to see. Whether it is something I simply failed to do correctly or if I find a faulty component.
Oh I can tell, I was more talking just about forgetting to include something in a post.
 

cyclops222

Lieutenant
Joined
Mar 21, 2024
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1,305
Do we have to sign up for the night shift ? :sleep:
I am felling really good for 2 days. If I take a 1 or 2 hour afternoon nap. I am up at 5 am and ramy Time for a coffee to really think about MY small list of all projects to do.
Remove floor boards and sweep up dead bodies. Buy a small B & D car vacuum. Use it in car & boats. Regrease all anchor pullies. Replace 1 dock line. Replace all twisted lines in little boat. Sand and refinish both oars. Grease all ends of Evinrude control cables. Refinish boat chair arm rests. Do a daily check why new Primer Bulb was deflated last morning. After 1 week of use. I need to print this work list.

Naahh Keep boating & sleeping on fishing trips. (y)
 
Joined
Jul 12, 2024
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Just wanted to pop in and leave at least a small update. After installing the venturi's back in these carbs it didn't seem to make a difference, but that's only because the actual problem hasn't been solved. I removed the flywheel revealing a "red" stator with a date code of 1998, once I removed it and revealed the trigger, it has a date code of 1988. Seems to be the original trigger and the wires are almost like wet noodles. Whether it's the culprit or not I ordered an OEM Mercury trigger, will be here Monday. One last discovery was the "red" stator, Mercury made these to replace the often failed factory stators, they came with an adaptor module that protects the switch box from over voltage, I think. According to the style of flywheel magnets you have, it determines if the stator wiring is reversed on the module, or connected to the same solid/solid w stripe wires on the module. Mine being the screw in style magnets, this module wiring was supposed to be reversed and it was not. I have no clue if this would cause any problems, but they put that in the instructions for a reason. There is a chance this might could have damaged the switch box but I will have to learn more about how that module works to know for sure. Sorry for the long post, I'm hoping to help the many others that have had the same problems with these motors. Should have another update within a few days.
 
Joined
Jul 12, 2024
Messages
23
Finally made some progress with the classic 50, removed and cleaned all connections at the coils. Not exactly sure what the culprit was yet, but was able to get this thing running at top speed yesterday. One thing to note, the previous owner apparently replaced the mercury tilt switch. This is the part that is mounted up above the starter solenoid and rectifier that looks similar to a condenser in an old points style distributor. It is a mercury filled switch that kills spark when the engine is tilted up. It was mounted incorrectly in a position that when trimmed down, it would seem to be about half way trimmed up. It has a slot on the back of it that is supposed to line up with dowels in the front plate on the motor. This had to be causing at least part of the problem. For anyone that doesn't know, the black/yellow wires are all spark kill wires, if any of these wires get grounded, it will kill the spark to the ignition. You can simply unhook that black/yellow wire from this tilt switch to bypass it in order to test it. Here's where things get confusing, after cleaning connections at the coils I did a few simple tests to try and eliminate possibilities. I had rapid/double spark on Cyl 1, so I swapped #1 & #2 coils to see if that rapid fire went to cyl 2, it did not. So then I swapped the leads for cyl's 1 & 2 coils on the switch box, and also swapped the wires at the coils. This makes no sense to me how this would affect anything but during the water test it came alive ! Did multiple pulls from a stop and it opened up every time. If I can narrow this down any further I will be back with another update !
 
Joined
Jul 12, 2024
Messages
23
Sounds like Shorts, and Internal Breaks in some Wires
That is pretty much the only conclusion I can come to as well. I started to unwrap the entire wiring harness coming from the switch box to the coils just to see. The coils are old, look to be original blue ones with mercury logos on them. I'm going to go ahead and put a new set on with some fresh plug wires as well.
 

BWR1953

Admiral
Joined
Jan 23, 2009
Messages
6,178
That is pretty much the only conclusion I can come to as well. I started to unwrap the entire wiring harness coming from the switch box to the coils just to see. The coils are old, look to be original blue ones with mercury logos on them. I'm going to go ahead and put a new set on with some fresh plug wires as well.
For my 1985 50hp, I bought a new wiring harness for less than $40 and also bought all new coil wires as well. The stuff that was on there was old and the new parts made a big difference.
 
Joined
Jul 12, 2024
Messages
23
*Final Update*
Alright I have finally got this motor running top notch. The problem came back randomly so that is what had me looking further into it. I figured out what was going on with the wiring so I wanted to post a final update so this thread will be complete. The culprit was simply bad connections on 2 different ring terminals at the switchbox. They appeared to be well connected and was even making contact every time they were checked for continuity. However under acceleration they were losing connection. I was able to cut all 8 of the terminals off at the switch box and the coils and crimp new ones on. It has been running perfect ever since ! Thanks everyone for the suggestions, I hope this helps someone in the future. Check those connections thoroughly !!
 
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