50hp evinrude..weak.

[EQCM2B]

I have a 1971 50hp evinrude. Model # 50173s serial # E07812. Ive been asking all sorts of questions about this thing and I appreciate all of the help that all of you have offered.<br /><br /> My latest troubleshooting trying to find out if I am overproped or not has revealed what I think may be a weak cylinder. I dont have a compression reading on them yet but when I followed your advice and removed the spark plug wires one at a time, each time I removed the top plug wire there is a noticable change in the engine. I can replace the top plug wire then remove the bottom plug wire and the engine will die almost immediatly. Is this maybe a weak coil on the top or do you think it is compression. The only reason that Ive been tinkering with it is because im trying to make sure that I need the new prop with a diffrent pitch that I asked about in a previous question.<br /><br />Again Thanks for all of the help.

 

[Fouled Plug]

Re: 50hp evinrude..weak.

It's easy enough to check the spark. If the bottom will jump a 1/4" gap, and the top won't that may narrow it down. Do yourself a favor and get a compression gauge. They can be found for around $25 and are invaluable for monitoring engine health and diagnosing problems. Good luck!<br /><br />------------------<br />Fish on! FISH ON! Holy cr*p, it's a whopper! Oh boy Oh boy! Oh, wait... It's just kelp.

 

[EQCM2B]

Re: 50hp evinrude..weak.

I got a compression guage from work. I've got @ 150 psi on both cylinders. Thanks for the info and advice.

 

[Dhadley]

Re: 50hp evinrude..weak.

What is the RPM at WOT with an average load? Make sure it's around 5800. Those motors were fairly sensative about being overproped.<br /><br />Good Luck!

 

[EQCM2B]

Re: 50hp evinrude..weak.

I've taken the boat out twice since posting the original question and found out a few more items that may or may not be part of the problem. When I first put it in the water with 5 people (@ 700 lbs.), I was able to get up to @ 20 mph at 4000rpm (WOT). After trying to pull a tube for about an hour everyone got back into the boat and I could barely make it over 10 mph and WOT would go no higher than 3000rpm. The engine data plate says this engine should run between 5000 and 6000rpm with a 50hp rating at 5500rpm. I'm starting to suspect dirty carbs or thermostat or both at this point. Each time I've checked the engine temp. it has always been cool to the touch. (no temp guage) Stupid thing is that I've never felt the temp after pullig a tube for an hour. I'll do this on my next outing. When I bought the boat it had been sitting all winter with a 3/4 tank of fuel (18 gal tank). I'm going to do the cheap fix first and try to spray carb cleaner down the carbs, if that doesn't do it then I guess i'll try to rebuild them. At this point I think I'm going to replace the water pump reguardless because almost all of the advice that I've read on the BB says to do it each year or so and since I have no idea when it was done last it's better safe than sorry. Any sugestions?