1980 evinrude suspect clogged exhaust

[Bgreen86]

I’ve been working on my 1980 evinrude 50. It has clean new carbs, new powerpack and coils, new stator and flywheel.
ive checked all the linkages and all seem to be right. The motor would fire up easy with almost no choking run great for a few minutes then start to bog almost like it was trying to jump in gear. This morning I fired it up after changing out the stator and fly wheel. It ran great for a minute then started blogging again before completely shutting down. After shut down the starter with new hot battery would just barley turn it over. Almost like it was seizing up. I pulled the spark plug as and tried again and it turned over wide open so I know it’s not locked up now. I think the exhaust has become clogged some how. I had the foot off of it two days ago the exhaust down there is all clean. Can the exhaust clog inside the power head some how? Anyone have experience with this?

 

[Crosbyman]

how's the tell tale steaming hot or warm

 

[Bgreen86]

Slightly warm. Very little water coming out of the exhaust relief ports up on the leg. Right before it did this the motor reeved up high and I had to shut it down. Then when I cranked it back it ran fine a minute then quit.

 

[racerone]

I have never seen exhaust blocked to the point of stopping a 1980 type Evinrude outboard motor !--I think that is a far fetched idea on your part.-But post your compression numbers.----Did you drain / refill gearcase with the proper oil ?----Torqued the flywheel properly ?------Did you install flywheel with proper fitting , clean and dry tapers ?-----Mixing gas / oil at 50:1 mix ??------I believe I have already stated that I would not leave the dock with this motor !

 

[Bgreen86]

All of the above done correctly fresh new gas mixed properly in new clean tank. Lower unit good. I’ve rebuilt several out boards and am a service tech by trade. This has me stumped. If I pull the spark plugs the motor will turn over no problem. Put the plugs back in and it will not. It’s being air locked some how just don’t know how yet. Obviously will not be leaving the dock with it as it’s one of many boats at my disposal. Guessing my next step will be to open it up and look for carbon build up. I do appreciate the help.

 

[Bgreen86]

Also 145psi on both cylinders

 

[racerone]

There is no carbon build up.------Pull the starter motor apart for inspection / testing ohms to ground / brushes / cleaning.

 

[Bgreen86]

Swapped out with brand new starter on hand still same problem plugs in barley turns over plugs out wide open. Alternate 1 plug out at a time and it broke free. Put both plugs back in turned over wide open about 15-20 revolutions and locked back up pulled plugs again relived pressure and it will turn over again

 

[jimmbo]

Sounds more like an Electrical Problem. Connection/Cable getting hot and a Rise in Resistance., Internal Battery Problem.

 

[Bgreen86]

Changed out starter again just to be sure 2nd new starter did turn it over better but still struggled. Would not start the motor.
battery is less than 2 weeks old back on charger now but still had enough juice to start a truck. Cables didn’t get hit to the touch but I’ll still change them out with a bigger and newer set later. I used my endoscope to look I. The cylinders and at the pistons everything inside looks pretty good normal build up on cylinders. Could use a little sea foam if you believe in that kind of thing. Just out of curiosity I pulled the engine out of the water and turned it over the exhaust gave a loud pop and fired up almost instantly. I shut it down just as fast. Scratching my head and letting battery charge at the moment.

 

[racerone]

Told you would not find any carbon !---Is there a factory key for the flywheel, yes, or not sure.-----Were the tapers clean and dry when you assembled that.----Did you torque the flywheel to 100 FT LBS ?----Are you installing NEW starters or other starters off your work shop floor ?----Take these starters apart for inspection !!.-----Easier to do than guessing , blaming anything else.

 

[oldboat1]

Blue stripe wire to upper coil/cyl, green to lower. Water in a cylinder (head gasket)? Flywheel key sheared/flywheel not aligned with key slot, throwing off timing?

 

[Bgreen86]

Fly wheel key is questionable if it’s original or not. does it fit properly yes. toque on fly wheel is a guess for right now however as my torque wrench is at my shop that I’m not allowed to go to right now because we are on lockdown. But I have torqued many and usually get them pretty close before checking. Everything under the fly wheel is nice tight and clean. My stator has a yellow purple a yellow blue and plain yellow. Hooked them up just as they came off. And the motor ran good with them like that before it stalled the last time. I will go to bigger and new battery cables as well and have a new solenoid. Again appreciate the help chasing this bug. I don’t normally have this much trouble with things. But I’m sure I’m missing something small

 

[SSboatman242]

Did you get it sorted out? Having this problem myself.

 

[GA_Boater]

Did you get it sorted out? Having this problem myself.

Start your own thread.

 

[anthony-g]

I know this thread is over a year old. But just for anyone searching and reading, I felt this comment is worth being added:

Yes. Absolutely do remove exhaust covers and inspect the ports. Clean away carbon buildup from the cylinder exhaust ports. Carbon buildup can and does occur, even if gradually over decades of use. In fact, the service manual covering my '72 25hp explicitly emphasizes the importance of that as part of routine maintenance.

Unfortunately, I only read that after losing my 25hp. Post-mortem: a chunk of carbon broke free from the upper cylinder exhaust port wall and severely gouged the cylinder wall and destroyed the piston and rings. Upon removal of the exhaust cover, I discovered and removed "massive" accumulations of carbon. In some spots, nearly 1/2" thick.

Prior to the powerhead's demise, it had developed symptoms of overheating and excessive drag. Though the exhaust was not clogged to the point of complete stoppage and motor seizure, it's easy for me to imagine it eventually reaching that point if the fatal event had not first occurred.