1973 25hp evinrude oil in exhaust and idle issues

[racerone]

What is different with the crankshaft that says the pistons need to be different ?

 

[jimmbo]

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.

The differences between the 18/20 HP and the 25 Hp 22in engine, were. Different Pistons that had the wrist pin closer the the Piston Crown, this changed the port timing relative to crankshaft rotation. It also lowered the Compression, so a different Cylinder head with less volume was used to restore, not increase, the compression. Larger Carb, Intake manifold, perhaps some mod to the Reed System. There might have been some differences with regards to the Timing Advance to Carb opening. A more precisely balanced Crankshaft rounded it out.

 

[anthill]

It's a model 25302, 1973? Yes it is the two exposed coils. Haven't pulled the flywheel yet. So much rain the septic tank backed up. Fun,Fun, Fun.

 

[jimmbo]

Before you go pulling the Flywheel, Replace the cracked coils, then retest for spark. If the engine then has spark on both Cylinders, I mean can it jump a 5/16" gap? If it can, I wouldn't be too worried a the points

 

[hardwater fisherman]

In my experience with the lo-tension magneto the condition of the points is very important.. They need to be super clean and checked for pitting. And proper gap.

 

[anthill]

I was looking at this motor today after running it a little on plane but mostly at slow speed or idle. I noticed a little oil on the lower unit. Probably not a big deal. But what concerns me is the little hole next to the oil fill level plug was obstructed by a piece of metal. There was a little bit of it sticking out of the hole. I got a grip on it with my finger nails and it snapped off the rest of the metal fell back down in the lower unit. Where could the metal piece have come from? Where did it go? Can I run the motor as is?

 

[54bobby]

the piece that you did manage to extract, was it aluminum/casing ,or brass/bushing, or steel/piece of a gear? if steel, you may be able to fish it out with a magnet through fill/drain hole but i would drain and open up gear case to inspect for damage and what the origin was.

 

[racerone]

That might be a factory " drain " for a cavity.-----Many folks panic when they see that leakage.----Some try to stop that leak with various means..----RTV is common or perhaps a nail as in this case.

 

[anthill]

Everyone that has responded, thank you. I found it. Pulled the lower unit.The hole is into the underwater exhaust channel. There was a large piece, about half a quarter size, and a couple of smaller pieces laying in the very bottom of the of the channel. They are all magnetic. I guess when I tipped the motor up the pointy end of the large piece fell into the hole. Still do not know where they came from. I could not see anything when I looked up into the exhaust housing that explains it. I took a look at the impeller, looks, felt new. Last I had it out it ran great so for now the coils and points can wait.