1973 25hp evinrude oil in exhaust and idle issues

[anthill]

Hi all,I have spent hours reading these forums and learned a lot. I have limited outboard repair experience but am trying.
This motor starts easily enough accelerates to wot with a stutter, shake at about 1/2 to 3/4 throttle. But it struggles to run at idle slow enough to shift into gear without slamming the lower unit. Got to be quick or it dies.
I have cleaned rebuilt the carb. It was spotless no varnish no corrosion nothing. I pulled the #5 core plug to clean the slow speed passages, nothing. I did not remove the #4 plug, should I? I did not replace the needle bearing just found out about it tonight on an old post. Needle valve looked fine. Float and seat and valve looked fine. reinstalled according to service manual. parallel and 1/16 above gasket. Spark will jump 1/2 to 5/8 across a Thexton spark tester. Installed new Champion UJ6J plugs instead of the UJ4J. Set the needle valve open one turn per the manual, changing the opening does not seem to have any effect untill it just shuts down. Adjusted the throttle cam follower. The plugs are very wet with a black fuel mix after a few minutes of run time and the barrel is covered in black oil. I run the motor in a 50 gallon barrel for short durations. I have at least 3 questions.
What next? What tool do you recommend for a compression test? What tool do you use for RPM's?

 

[racerone]

Check the thermostat.

 

[anthill]

Thank you the t-stat was stuck 1/2 open. Will run it to check.

 

[racerone]

That is a very common failure !

 

[jimmbo]

What ratio are you mixing gas-oil?

Are the points gapped properly?

 

[F_R]

Remove the fuel pump from motor (don't disconnect the hoses). Now give the primer bulb a squeeze. If gas comes out the backside of the pump, the pump diaphragm is shot and flooding a cylinder.

Those are not clean-running motors, and you will never get it to stop producing black gunk in a barrel. But it will be a lot better if you get it running properly. Or on a boat where it was designed to run.

 

[anthill]

jimmbo I use 50 to 1 ratio. Will have to check the points. It is not something I have ever done.
FR I will test the fuel pump.
I ran it on the boat 2 days ago. Its a long story way it took so long to get it in the water. It was running fine at about 3/4 throttle and suddenly lost almost all RPM. Just "bogged down". Did not stop. Chugged along for 20-30 seconds and caught back up and took off. Fuel bulb was hard. Idle was much better. Compared to other motors I have had it uses an enormous amount of fuel. Ran on plane (14' polar craft) for an hour and idled for another hour used 4 gallons. Any help would be much appreciated.
Thank you both for your help.

 

[anthill]

Should I start a new thread with additional questions or keep this one running?

 

[kbait]

The 3/4 throttle and sudden slow down sounds like an ignition issue.I would pull flywheel, remove/clean point faces, check for any side to side play in armature plate (any play changes point gap/timing..post back if there’s play), gap each pointset to .020” at widest opening, new J6C plugs gapped to .030”. You’ll likely have a sweet runner afterward.
Good luck!

 

[anthill]

J6C hotter? or just a better application for this motor?

 

[jimmbo]

A J6J is a hotter plug than a J4J, Some people(I wouldn't) run a hotter plug if they idle a lot and rarely, if ever, run wide open

You said the plugs were wet, that happens a lot at lower speeds, You need to read the plugs after the engine has been running a WOT for a while

 

[54bobby]

those 22 cubic inch 25"s are first of all, 2 strokes, 2nd of all they're high performance versions of their little brother 22 cuber 18hp's by way of a different cam, carbs, pistons, and a couples other mods. you will never get a high revving 454 chevy motor with a race cam to idle like the same engine in the oldsmobile 98. lol these little 81 lb engines, (1 lb. heavier than the 18 hp) are built to run as in scream. they're operating rpm range was i believe, at least 500 rpm's higher than any other omc outboard of the same era. point gap and cleanliness, the right plugs gapped properly, coils, and don't overlook the plug wires are a must. as mentioned above the smallest undetected pinhole in the fuel pump diaphragm will drive you nuts. clean fuel, and propper lync and sync are a must and check the o ring in your fuel line, you don't wanna be sucking air in till the engine wants it. as long as you have good compression, and proper maintenance, these motors are screamers and will continue to be so long after much newer 4 strokes are dead and buried. i have a couple and like all thoroughbreds, need proper care with which will keep your 14' boat with only 8 or 10 inches touching the water with just you and no gear at wot for years to come.

 

[anthill]

jimmbo I knew that the j6j is hotter than the j4j but what is the j6c kbait mentioned. Now that the idle is better I may go back to the j4j. Or run out on the j4j and switch to the j6j to idle and slow troll.

 

[anthill]

54bobby is lync and sync same as throttle cam adjustment?

 

[jimmbo]

The J4J and J6J plugs are not being produced anymore(those there may still some in stock at dealers. The J4C replaced the J4J, and the J6C replaced the J6J

Careful with frequent plug changes, in that you don't strip the threads

 

[racerone]

What different " cam " would you find in the 25 HP versions of this 22 cubic inch motor ?

 

[54bobby]

54bobby is lync and sync same as throttle cam adjustment?

yes, but there is small differences between the 22 cubic inch engine models and years. some the throttle is supposed to start to open a 1 certain spot on the cam markings and others a different spot. either a hair before the roller is centered or centered or just after. the celic manual has all the years and there setting points listed. get the celic manual and i also sugest getting your model and hp specific shop manual. a 1967,8,9, and i think up to 1975 or 6 18 and 25 hp engines are 95% compatable in repairs and parts. it's the other 5% that the 25hp models throw you the curve. carbs, cam, pistons come to mind. you can take a 9.9 amd pretty much make a 15 out of it with a couple changes. you can not convert an 18hp to a 25 with simple part swap outs. the 25 is high performance. if you do a ton of trolling grab an 18 fastwin from the same era. much better at low speed. put that 25 on a 14' tin and make a sleeper out of it.

 

[anthill]

So I took the cover off and both coils? are cracked. Looking for something else to use while I get this one back in shape.

 

[hardwater fisherman]

If it is a 1973 model it should have external coils. What cover did you take off to find cracked coils? Flywheel? If you are talking about the driver coil under the flywheel they do look kind of strange even when new.Any ways there should only be 1 coil under the flywheel if it is a 1973 model.

 

[54bobby]

What different " cam " would you find in the 25 HP versions of this 22 cubic inch motor ?

my bad, not the cam. i meant crank shaft. beer and forums with grand kids in the background. lol. and the different crank is why the pistons needed to be different.