Re: 1964 3 HP Evinrude (model #3402) Can't get a spark. Please help a newbie.
I don't think you're doing something wrong - you gave it 4 or 5 good pulls right? If so, this tune-up is going to move to a more advanced project.<br /><br />There's a few possible reasons for low compression. One is worn or scratched cylinder walls & rings. Generally speaking on small engine's that's fatal. The second possibility is that the head gasket is blown. On a 3hp that's very unlikely, and it often results in uneven or no compression anyway. A third possibility is that the pison's rings are stuck in their grooves. This is a fairly common problem on these especially if they're over-oiled and never decarbed (maintanance process that removes deposited carbon from the combustion chamber).<br /><br />With luck we're looking at #3 but freeing those rings is going to be a real challenge. You can try turning the flywheel until the pistons are about half-way up the cylinders (to close off the exhaust and intake ports), then set the engine carb down and put a few teaspoons of decarb solution (like seafoam) in each cylinder. Then wait a few days and check your compression again.<br /><br />If you're going to proceed with a tear-down, read through the entire powerhead section before proceeding so you know what you'll be doing. Also, check back here to see if anyone else has a better idea.
I don't think you're doing something wrong - you gave it 4 or 5 good pulls right? If so, this tune-up is going to move to a more advanced project.<br /><br />There's a few possible reasons for low compression. One is worn or scratched cylinder walls & rings. Generally speaking on small engine's that's fatal. The second possibility is that the head gasket is blown. On a 3hp that's very unlikely, and it often results in uneven or no compression anyway. A third possibility is that the pison's rings are stuck in their grooves. This is a fairly common problem on these especially if they're over-oiled and never decarbed (maintanance process that removes deposited carbon from the combustion chamber).<br /><br />With luck we're looking at #3 but freeing those rings is going to be a real challenge. You can try turning the flywheel until the pistons are about half-way up the cylinders (to close off the exhaust and intake ports), then set the engine carb down and put a few teaspoons of decarb solution (like seafoam) in each cylinder. Then wait a few days and check your compression again.<br /><br />If you're going to proceed with a tear-down, read through the entire powerhead section before proceeding so you know what you'll be doing. Also, check back here to see if anyone else has a better idea.