Hello, I have a 1963 evinrude light twin , 3 hp , it was running (not well) but is now not running, I checked the compression and found it 60# in both cylinders. Is this part of my problem? the compression is the same in both. thanks
low compression can easily cause it to not fire and have far reduced power. the gas wont be able to be compressed enough to combust when sparked. it can be caused by bad valves, bad valve gaskets, bad piston rings, or just normal wear due to old age.
bad valves can be replaced and fixed, as can there gaskets. over time the gaskets wear out causing the valves to not make a tight seal with the block which causes reduced compression. the valves could also be damaged from overheating or normal wear from old age.
if the rings are shot then you need to disassemble the block and remove the pistons to replace the rings. the rings could have gone bad due to old age and normal wear or from overheating. lack of oil causes greater heat, friction and wear.
if its old the block itself could just be worn out and to fix that would require (i assume) reboring the block for slightly larger pistons. i know, its not exactly an ideal or logical thing to do, but it would work...theoretically
sorry, didn't know it was a 2 stroke
not that knowledgable on what each engine has and mostly just rough guess based on things that i know can cause various problems based on experiences.
Considering that the only way to check compression in that engine is to use the pull starter, I don't think 60 psi in each cylinder is all that bad. It would be nice to see a bit more, but I don't think the values that you obtained are fatal, especially given that they are very even.
That is an extremely simple engine and whether of not it is going to run well goes to the two basics - spark and fuel. Pull the flywheel (harmonic type puller only, please!) and check the points for condition and gap. If the points are pitted, I would replace them along with the condensors. If there is any cracking in the coils at all, replace those also. If they are without cracks, they may or may not be ok. At this point, I would set the gap for the new points and reassemble - you can then use a park gap tool to check for spark.
If all is well in the "fire dept," next on the list is fuel. I don't have a parts diagram handy for your motor, but if I remember correctly, it has a built in fuel tank and gravity feeds fuel to the carb. That being the case, there is no fuel pump to worry about. As a gravity feed motor, however, proper venting of the tank is very important. I think I remember there being a vent screw in the tank cap, so be sure to check that for proper air flow - starting with whether or not it has been opened enough to insure a clear breathing point.
Like any other carbureted motor, this one needs to have a clean carb. If you are not sure of the carb's status, it may be time for a rebuild kit. The hardest part about rebuilding these carbs is that they are little and you feel like you are working in miniature. That said, I have rebuilt them in the back of a boat, while keeping an eye on the bobber of my fishing pole for evidence of a fish strike! While you are rebuilding the carb, it makes a lot of sense to replace the fuel line because it is really frustrating to rebuild a carb, only to have it clog again due to a deteriorating fuel line.
And, while you are doing all of this stuff, you may as well check the waterflow from the water pump. You will have to wait until you get all the other stuff done and the motor is runnign OK, but its an easy enough task. Run the motor in a barrel to see what is coming out of the motor in terms of cooling water. This motor should have the small oulets, 4 to a column (2 columns) on the backside of the midsection. Don't be fooled by the fact that the 3hp model doesn't pump a whole lot of water, but be sure that your are seeing a constant stream of it in the form of a fine mist coming from the outlets. You should also check the powerhead for excessive heat. Once again, I don't have a manual for your motor, but I can tell you that normal operating temp for the later, 4hp motor is 163 degrees, measured on the side of the cylinders. Don't try to determine temp at the head because it will run hotter than that.
Last on the list is the gearcase. Yup, I know I am getting slightly off topic, but what the heck, while you are doing all of this, might as well replace the gearcase oil. I believe that this motor takes "Type C" lube so be sure to get the right stuff to refill it. Since Type C is no longer available for the most part, you will want to use the OMC "Premium Blend." This oil meets the Type C standards so you will be fine. Don't forget to put new O-Rings on the gearcase plugs!
I just learned in another thread about a 3hp motor of your vintage, that they have a fuel filter built into the bottom of the tank. You might want to check that and go read the other thread that is on the boards now.
Also, I had forgotten about the petcock on the tank - you'll want to make sure that its open all the way and not obstructed.
I realised that I never told everyone what the problem was. It turns out the motor kept fouling the plugs. At my elevation (7000 ft) the carb was getting too much fuel. As the main jet is non-adjustable, I peened the jet wirth a small hammer, and the motor has been running great since then.
well, desperate times, desperate measures... I adjusted it gradually with running tests in between, till I got the sparkplugs a tan rather than oily color.
This is how the natural gas guys adjust our gas appliance jets up here to compensate for elevation.
1963 3 hp evinrude low compression?
Linear Mode
