MaverickSRX
New member
Hi all, First time poster long time watcher/reader on this site.. I'm at wits end. Can't figure out whats wrong with my motor. I'll start at the beginning. I bought a boat with the 1975 Evinrude 50hp #50573B in summer 2021. the boat/motor sat for 8 years. I get the motor running without much difficulty. I couldn't believe how good it ran after sitting so long. I install new impeller pump kit, change gear oil, compression test both cyls. at 130# each. I fix boat up and take it out in the fall and motor runs like a bear, high speed, low speed and at idle. fish it a few times before putting it away for winter. Spring 2022 go fishing a few times motor ran good. Then started running rough.. Would start good ,run good out of marina run like a bear to fishing spot shut down troll with kicker motor few hours. Start the 50 up to go back and while warming up just run rough missing wanting to stall. It would run back to marina like a bear ,high speed, idle down in marina miss ,sputter etc. I remove carbs and rebuild with new kits, carbs surprisingly clean. new spark plugs NGK's. run in driveway on muffs runs great. take out to the lake and starts out good run it around and run great at high speed then starts running rough missing at idle/low speed. Then I read on here Evinrude don't like NGK plugs so I put new Champion L77JC4's back in. I do a spark gap test and have nice blue spark 1/2 inch gap. Take it out and same issue. Frustrated I let it sit in garage and use my bigger boat for fishing etc. After awhile (week or so) I start checking the motor out and pull spark plugs and they have water droplets/moisture on the electrodes both plugs. I do compression test both cyls. at 130#'s. clean plugs take boat out run it same issue at idle low speed.. check plugs as soon as i get home about 20 minutes plugs are dry light tan/brown burning looking good. Put plugs back in motor check a few days later (in a dry garage) and they're wet with water/moisture. (Really scratching head now !!!!) I come back to here to try to find a answer and read somewhere that it could be exhaust manifold gaskets leaking???? How can the plugs get water on them after just sitting in the garage????? In the fall I pull the powerhead to work on over the winter. I order parts from MarineEngine.com. Exhaust manifold gaskets, new thermostat, cover plate gaskets, lower crank seal since i got it apart, fuel pump rebuild kit, mounting base gasket. I do the work all the gaskets looked good. do the crank seal and find the seal it rubbed through can see the spring through the rubber. crank shaft sealing surface is good no groove. I figure finally i found the problem !!! Spring 2023 i run the motor in the driveway in a barrel for about a hour never skipped a beat idled great. Take it out ,ran great low speed in the creek to the lake. run it around the lake ran like a bear. Idle it down ran like **** missing, sputtering, died, started hard, give it gas runs great medium/high speed. get back to dock pull motor cover and notice coil arching to block. (it was a dark cloudy day). Get it home found both coils cracked. figure i found the problem. Order 2 new OEM coils kits from here. Install new coils do a spark test good spark but if boot was close to a ground it would spark to ground instead of through tester.. take the boat out ran great idled great ..yea i finally fixed it, I thought... go fishing ran good. trolled with kicker started 50 to go back started missing running /idling like crap like dropping a cyl. then would idle good then miss again.. run back to dock like a bear. I ohm test eveyrthing check clean all grounds. check post here and other sites, probably a power pack. install a new power pack , new stator and new trigger/sensor and guess what SAME PROBLEM!!!!!! The problem is after running hard getting it hot (its not overheating) you idle down and it starts missing dropping a cyl always #1. It starts arching between the spark boot and the hex head on spark plug then it stops arching and runs good then its starts aching and missing i took a video at night you can see and hear the difference. I swapped coils, changed plugs and it always on #1cyl. I did find moisture on the plugs again.. Its been a few weeks since i looked at it. I never post before but I'm at a loss what to do next. could it be moisture grounding out the plug ????? head gasket?? i still have 130 lbs compression bth cyls. IDK .. Help Please.. sorry for the novel lol.. TIA !!!! I can post pics once i figure how to do it..