Hey, those little 3hp Evinrude Johnson motors are great!!!
I have 4 of those!!! One I am currently rebuilding!
1957 Evinrude 3hp (80 psi upper and lower)
1958 Evinrude 3hp (78psi upper and 76psi lower)
1959 Evinrude 3hp (75psi upper and 75psi lower)
1965 Evinrude 3hp (rebuilding) ( 0 psi upper and 68psi lower) had blown head gasket!
If, you can tolerate a little advice about those motors, then I have some. :LOL2:
Originally, those little motors had bushing connecting the wrist pins and connection rods to the crankshaft. They continued the same set up until 1968. The reason I am bringing this up is that running the motor with a fuel to oil 50:1 ratio will short life that motor. I know that is the "manufacturer" recommendation.
The original fuel to oil mix ratio was 16:1. The motors with the bushing needed a lot of oil to prevent wear and protect the bushings, crankshaft, wrist pins, and cylinders and rings. A lot of the older motors still have good compression despite having years more of run time on them.
The manufacturer went to 24:1 to around 1960 to 1963. Then went to 50:1 1964 and there after. They did this because the rest of the larger motors already went to needle bearings and thus need much less lubrication. Also improvements of the 2 cycle oil was an added bonus as well. Prior to the 2 cycle oil improvement regular SAE 30wt non detergent motor oil was used in all motors.
The reason I am going through all this song and dance is to let you know that 50:1 fuel oil ratio is not sufficient oil to protect that motor from wear and tear. You motor still has bushings!!
I would recommend using a minimum fuel to oil ratio of 24:1. I use 16:1 in all mine (3hp motors Evinrude Johnson motors, but that is a personal choice because that is what they original call for and the added oil helps protect my motors). The extra oil will not harm your motor!! Seafoam can take care of any extra deposits.
The 24:1 fuel oil ratio will give your 1965 Evinrude added protection from wear. You stated that the mechanic stated that you had 60psi compression in your upper and lower cylinder. That is low minimum for your motor. It shows that a lot wear has taking place already with using 50:1 ratio.
Try adding a 1 or 2 ounces of Seafoam (can be found at most auto stores) to each gallon of fuel oil mix. It will help decarbon your the inside of your motor's rings, cylinders, exhaust ports..etc.
At first it will smoke at bit more, but that is because the Seafoam will be removing the carbon in the engine and then after about a tank or two it will run will a lot less smoke, like normal. Continue the Seafoam from there on and you will help keep your motor clean and prevent gumming up. The Seafoam is very safe for your motor and been around for about 40 or 50 years. Hopefully your lower compression is from semi stuck rings and preventing good compression. Hopefully the Seafoam will removed the excess carbon/coking and free up the rings and you will get better compression with improved running.
I have several buddies that are semi retired mechanics on the AOMCI(Antique Outboard Motor Club Inc) forum that will testify, even with the great advancements and improvements of 2 cycle marine motor oil (TW-C3) that 50:1 fuel ratio is not enough oil to lubricate and protect the 3hp Evinrude Johnson motors from 1968 and prior!!
24:1 fuel oil ratio is 5.3 oz of oil per one gallon 87 octane gas (but who is going to measure 5.3 ounce....just put 6 ounce and been done 8) ). Then added your 2 ounces of Seafoam and mix it up and your golden!!
Well, I think I have talked your ear off!!! I'm glad you got that little beauty running again!!! Oh, don't for get to check and replace your lower unit oil (any marine grade 80wt to 90wt gear oil will do )and replace your motor with a good impeller (water pump).
Here is a parts diagram for your motor!!!
https://www.marineengine.com/parts/vintage-evinrude-johnson/380570/catalog.html?https://www.marineengine.com/parts/vintage-evinrude-johnson/380570/38057000001.htm
Give a yell if you need help!!
