Motor wont start....help please

[macahillsho01]

I have a 1975 Evinrude 25 hp. model 25553B. We got this motor with our pontoon and just cant seem to get this thing started. I hooked up a spark checker and both coils seem to work. Rebuilt carburetor, new fuel lines and fuel pump/filter. Made sure kill switch is correct. New spark plugs. did a compression test and have 65 on top and bottom cylinder. Top cylinder looks like has some carbon. Bottom cylinder looks like dusty dry. Was wondering if i need to have the neutral safety switch hooked up because there are no wires for it. Im guessing they just bypassed it??? Does anyone know what i should be looking for , or maybe I am doing something wrong. Any help would be greatly appreciated.

 

[Geoffrey Graydon]

If you have a cylinder that stays dry you are not getting any fuel through.try removing the line where it arrives at the carburetor and crank over,if no fuel,pump problem.If you have fuel,carburetor problem. does your spark jump a 5 1/16 gap on your tester.

 

[racerone]

The neutral switch has to with electric start motor.---Not spark.----So does spark jump a gap of 1/4" or more ?---I say you have weak spark.---Or the high speed orifice plug inside the carburetor bowl is plugged.

 

[Bobbywolf]

Something to more to check, after you have confirmed spark and fuel, is the flywheel key. Partially sheared will throw timing off enough you can't get it to run right. Fully sheared and it won't run at all, but you will have spark, just at the wrong time.

Get your fuel sorted out first. A choked engine, being turned over but not starting should be dripping with fuel from all carbs.

 

[racerone]

This motor has breaker points !----When the key is fully sheared there will not be any spark.

 

[Bobbywolf]

This motor has breaker points !----When the key is fully sheared there will not be any spark.

Ah ha! I overlooked the year. Very good point.

 

[James R]

Did I miss something here. Compressions at 65. That motor is worn out.
I have worked on a variety of Johnson/Evinrude 25Hp motors. Haven't seen one working properly that has not been at least 100Psi. A good one will be at 120Psi. Mine is. Pull the cylinder head and take a look.

 

[Crosbyman]

try a good decarb product Merc POwer TUbne ... a bottle of seafoam in a 2gal of fresh agas...

some like seafoam some don't .. but try it

 

[oldboat1]

I'm one of the seafoam nay-sayers -- but mostly when left in the tank (empties tank debris into the carb, imo). Flushing out the engine like Crosbyman suggests is a different story.

 

[James R]

I have never used sea foam and don't intend to. The compressions are very low. If sea foam removes carbon as I hear it is supposed to, that wont improve compressions. If the rings are stuck then something like ring free might do it but again I doubt it. To get the best idea of the condition of the cylinders removal of the head is necessary. Or am I barking up the proverbial wrong tree and the compression tester is wacky.

 

[racerone]

Simple to remove bypass covers on these to have a look at pistons / rings.

 

[Crosbyman]

After peeking in the bypass covers or pulling the cyl head one would still be at step1 to recovery.

A can of decarb product may or may not help but as far as Seafoam it seems to do some improvements compression wise see video .

I have used it on my snowblower with sneezing and popping and it cleared it up nicely. I had ordered a new carb but it is stored way.

Is Seafoam better than outboard decarbs...I do not know but if these products used as a least cost step to save on time, labor and parts it remains a personal decision but at least a new compression meter may be a wise move for O.P.